A: What is the best underlayment for a tile roof? Our house in Los Angeles is 25 years old. One roofer recommended removing the composite roofing tiles and replacing the old underlayment with 90-pound paper. Then they will replace the roofing tiles. Another roofer recommended the same approach, but with two layers of 30-pound felt as the underlayment. Please explain the differences between paper and felt and the differences between using the 90-pound paper and the 30-pound felt? Is one better than the other? — Irene
Q: With a tile roof, the underlayment and flashings are critical as they create the primary water barrier. The tiles are mostly for aesthetics and to help protect the underlayment. Since the tiles, themselves, should last 50 years or more, the underlayment should be of similar quality. More often than not, the tile roofing outlives the underlayments and flashings.
The terms “paper” and “felt” are used interchangeably and refer to organic felt paper, which is impregnated with asphalt and fillers to make roofing shingles and underlayments. Some products use fiberglass mesh rather than felt as the substrate.
The term “90-pound paper” usually refers to gravel-coated roll roofing, which is a low-quality product that rarely lasts more than a few years when exposed to the elements. It weighs about 90 pounds per square (100 sq. ft.) because of the heavy gravel surface. I would not recommend it for anything other than a utility shed as the quality today is very poor.
Two layers of ASTM 30-pound asphalt-impregnated felt is the minimum you should use under tile and should last 20 to 30 years. For a little more money, you can upgrade to a double layer of heavy-duty, SBS-modified asphalt underlayment such as VulcaSeal G40 (Fontana), Layfast SBS T35/43 (MB Technology), or Right Start UDL (Malarky Roofing Products).
Two-layer installations often have twice twice the warranty period of single-layer installations. Read more on Installing Two-Ply Underlayment.
The fiberglass mat, SBS (synthetic rubber) additives, and 40-pound weight can increase the lifespan of the underlayment by 50 to 100%. Torch-applied membranes of organic or modified felt are commonly used as the second layer (the “capstock”) in wet areas like Florida, but are probably overkill in an arid region like southern California.
There is a distinction between standard “30-pound” felt, which actually weighs 15 to 20 pounds per square and ASTM-rated #30 felt which weighs closer to 30 pounds and is of higher quality. ASTM-rated felt (under ASTM D4869 or the older D226) is manufactured to strict specifications, while standard 30-pound felt varies in quality from one manufacturer to another. Both are made with an organic felt mat impregnated with asphalt and various fillers. Some premium asphalt underlayments use a fiberglass mat instead of felt paper.
Many roofers now prefer synthetic underlayments, which are lighter, more tear-resistant, and easier to work with than felt paper. There are wide variety of these with different warranties and projected lifespans. As with any new product, however, how long they will really last is unknown and manufacturing standards have not yet been established.
Whatever underlayment is used, the installation is as important as the specific material. Most important are proper sealing and flashing at all penetrations for chimneys, skylights, pipes and roof vents. Valleys are also a problem area that need special treatment.
I prefer an open valley design using a self-adhesive flashing membrane (such as Grace Ice & Water Shield) as the underlayment, covered with a heavy-duty metal flashing. Avoid aluminum flashing as it is will fail long before your tiles.
In some markets, it is becoming more common to cover the entire roof with peel-and-stick, self-adhesive (SA) membrane. This is typically bonded directly to the roof sheathing. SA membranes self-seal around nails and other penetrations, can be exposed to sunlight for extended periods, and aggressively sticks to just about any material. It is a good choice for roof coverings that are easily penetrated by water — such as low-slope tile roofs in an area with windblown rain. For that reason, this approach is catching on in parts of Florida and the Gulf Coast. The main drawback, is that the underlayment is nearly impossible to remove when it comes time to reroof, so you may need to tear off and replace the roof sheathing at that time. — Steve Bliss, BuildingAdvisor.com
Robert C. says
Peel & Stick vs. Modified Felt for Arizona Roof
We are obtaining bids for tile roof replacement in Tucson, AZ. Most of the bids are recommending two layers of SBS underlayment (various brands). However, one contractor is recommending to use MAT 40 by Bitec. He says we would only need one layer because it is thicker and tougher. It is SBR type which more rubberized. He is our preferred contractor so I have pressed him on the one layer issue. I also called Bitec in Arkansas (it is made in USA) and discussed with their technical rep. He also said one layer is OK and they sell most of their product in AZ and FL. He said their product has been in use for 30 or more years, so it is well tested in real world use.
What do you think of MAT 40 and using only one layer? Very appreciative of you opinion and help!
There are now many options for roofing underlayment. But with tile and other high-end roofing, most high-quality contractors use either two layers of rubberized asphalt or one layer of peel-and-stick, such as MAT 40.
Both systems have a proven track record and each has pros and cons. MAT 40 and other premium peel-and-stick membranes are the closest thing you can get to a guaranteed waterproof roof. The material seal around any nail or screw penetrations, aggressively sticks to itself at seams and to any clean material, and is ideal for sealing around skylights, chimneys, step flashing, and other roofing transitions where most leaks occur. In the event of a blow off, this is the underlayment most likely to stay in place and protect the building.
The biggest drawback is the difficulty removing it when re-roofing. You choices are often to either leave it in place or to tear off and replace the roof sheathing – a costly process. If you use a peel-and-stick in your climate you need to choose one that is rated for high temperatures like MAT 40.
Two layers of SBS-modified asphalt is also a good system and a big improvement over traditional roofing felt. It is more durable, flexible, tear-resistant, and waterproof. They seal moderately well around penetrations, but cannot be considered waterproof at nail holes. With double coverage, you’ve got a secondary barrier in the event of a hole or tear. Detailing around transitions and penetrations requires standard flashing and sealing details. The service life should be comparable to peel-and-sticks.
You can read more about Peel & Stick for hot climates at this link.
Joe Marcin Jr says
OK To Staple & Leave Old Underlayment in Place? Valley Techniques?
Great articles – I’m considering Fontana G-40 for my underlayment in Arizona. Should this be nailed or stapled to the roof? Can this be applied over the existing underlayment that is not leaking? And is it best to use self adhesive material in the valleys?
This roof is 17 yrs old (tile) and I am doing this as preventative maintenance as many roofs in my community have leaked due to poor contractor applications
If you use staples with Fontana G-40, you void the warranty and get an underlayment more prone to leakage. Fontana states:
The industry standard is to strip the original underlayment. It may look good now, but it probably won’t in 20 years. Also the contractor is unable to inspect the roof sheathing for wood decay or other damage that you would want to fix. Sometimes contractors leave peel-and-stick underlayment in place due to the difficulty in removing it, as well as its longevity and water-tightness.
As for the valleys, self-adhesive bituthene underlayment is usually the best option. Even if you use a metal valley flashing, use a sheet of bituthene under the metal. Installed properly, it creates the most waterproof barrier in the places you need it most.
You art absolutely right to focus on products with high-temperature ratings in addition to their overall performance and longevity. In your climate, I would look for products rated for long-term exposure to temperatures over 200°F.
Most roofing underlayments publish a high-temperature service (or application) temperature, but not all. Above this temperature the material may start to soften, flow, degrade. As you point out, many plastics and other materials fail prematurely in extremely hot temps.
In the absence of long-term test data, companies use accelerated testing techniques to simulate long-term performance. How well the simulation represents actual field performance over many years is open to question. But testing to established industry standards (e.g., ASTM or UL) carries a lot more weight than marketing claims pulled out of thin air.
Some high-temperature products are labelled HT, like Boral TileSeal HT (now owned by Westlake), while others like TU 43 are rated nearly as well, but you would only figure that out by digging into the data sheets.
If you’re looking for a peel-and-stick membrane underlayment for valley flashing or the entire roof, Grace (now GCP) Ice & Water Shield has the longest track record, having introduced the material 45 years ago. Their HT version is much newer, but it’s a reasonable assumption they Grace knows the product type as well as any competitors.
Ro M says
2 Layers G40 Vs. Boral TileSeal – Which is Better?
2 layer GTA 40# rubberized Vs. 1 layer Boral Tile Seal underlayment material
I am in Phoenix area. I am trying to finalize between 2 contractors with different underlayment options. Each is offering 20 year warranty on material. First contractor wants to install 2 layers of GTA 40# rubberized underlayment (for about 5-10% more price) and is offering only 5 years on workmanship, unless there is defect with material and then the manufacturer will cover 100% . Second contractor wants to install only 1 layer of Boral Tile Seal and is offering 20 years on workmanship. He thought the wt. of the Boral Tile Seal is most likely 60#, but could not confirm. Which option is better for the long run, for the AZ weather? Both contractors are pretty highly rated in the area and have good reviews posted on line.
Short answer is that both are good choices and will probably last 20 years-plus. Which will last the longest in AZ is impossible to say. Both product types have been around for 20 years or more although the specific formulations are newer and have not been used long enough for definitive answers. A two-ply installation of G4O is comparable to a single layer of TileSeal.
VulcaSeal G40 is similar to traditional roofing felts but uses synthetic rubber (SBS) additives to make the product stronger, more tear resistant, and longer lasting. Boral TileSeal is a variation on the peel-and-stick membranes first used in the 1980s as roof flashings in cold climates. The new high-temperature versions like Boral Tile Seal HT (now Westlake TileSeal HT) is tested up to 250 degrees F and has all the necessary approvals, including Miami-Dade Country.
I cannot find published temperature data on G20, but other similar products are rated to above 200 degrees F., so should be OK in your area, where roof deck temperatures may exceed 150 degrees F. However, it wouldn’t hurt to check with the manufacturer.
There are pros and cons to each approach. For the best water seal around nail holes and other penetrations, nothing beats peel-and-stick membranes. They are a good choice for slow slopes and areas that get heavy wind and rain or snow. Their main downside is they are difficult or impossible to remove when re-roofing. Your choices are to leave them in place or replace the roof sheathing.
Two layers of modified (rubberized) asphalt is a well-established approach that should outlast traditional asphalt felt by 50% or more. It provides pretty good sealing around nail holes, but not perfect. It is easier to repair and replace if necessary.
As for warranties, they provide a rough indication of the manufacturer’s confidence in a product, but are usually worth less than expected. Most roofing product warranties are for materials-only, prorated for years in use, and have plenty of loopholes for installation errors, exposure time, etc. In many cases, “certified” installers of a given product are able to offer longer warranties for the same product.
Greetings. I am also in the process of getting new underlayment and going through quotes like crazy. It seems as though prices have gone up but what can you do , right? I am slimming down on the choices of companies that I am considering of hiring. I have been given the options of Westlake Royal Tile Seal HT, Komodo, MB Technologies Layfast SBS TU-43 Synthetic Underlayment. I am in the heat of an area in between Tucson and Phoenix, AZ. It gets real hot and I am sure that the roof is even hotter. How do they last with extreme heat? Usually with synthetic material, in the heat, either stretches, warps, melts, or cracks and totally falls apart from being exposed to these temps in AZ. I have had plastic do all these things in the heat of Arizona. I have seen plastic melt before my eyes in this heat. So the main question is what to pick? Surely the materials that are newer to the industry have yet to experience the long term affects on their products. What to do? Thank you for your help and knowledge.
Mar T says
Which Self-Adhesive Underlayment is Best?
I’m getting different bids from roofing companies here in AZ where we get heavy wind driven rain throughout the monsoon season (June – end of September). Some companies use either single layer or double layer 40# felt. Most often lately, the roofers are wanting to either use APOC Weather Armor Ft3, Polyglass TU Plus, or Boral TileSeal HT….
All have 30 year warranties… but is there a better self adhering underlayment that others?
Comparing one product to another, however, is difficult as none of the newer products have been around for more than a few years. Apoc Weather Armor was introduced a year ago in 2021, PolyGlass TU Plus was introduced in 2006, and Boral Tile Seal HT (now owned by Westlake) has been around since around 2016.
Since none of these products has existed for close to 30 years, there is no field data to establish their service life. Some companies do accelerated testing to simulate long-term conditions, but laboratory conditions don’t always correlate with real world performance. The only self-adhesive membrane with a 30-year track record is Grace Ice & Water Shield (now ACP), introduced in the late 1980s.
On the plus side, the three products you mentioned are all premium products from well-established manufacturers, all have high-temp ratings from 260 to 265 °F, and all are approved for use in Miami Dade County, which has some of the toughest roofing codes in the country.
Two point to bear in mind:
1) Installation is as important as the specific product chosen, so go with a contractor you can trust. Some membranes require primers on the sheathing and all require a dry, clean, and undamaged substrate, along with even hand-pressure or a roller for a good bond.
2) Most roofing product warranties do not include labor and are pro-rated from the installation date. Also they have plenty of loopholes. While they say something about a company’s confidence in their product, but their actual cash value is limited.
Nat Chiaffarano says
Can You Place Peel-And-Stick Over Hop-Mop?
In south Florida our roofer is suggesting mopping tar over the sheathing and then 30# self adhesive rubberized felt paper under the ceramic files. Is this a good way to go?
Florida has one of the strictest roofing codes in the U.S. It allows several options: hot mop, peel-and-stick adhered directly to the sheathing, peel-and-stick applied over mechanically fastened felt, or two layers of an approved felt or synthetic underlayment. Another option is to tape the roof sheathing with 4-inch peel-and-stick and then apply one layer of an approved felt or synthetic underlayment.
The code goes into detail about the number of plies, lapping, and types and placement of fasteners. There is no consensus on which system is best, but most roofers still prefer traditional hot mop or have switched to peel-and-stick. Each has pros and cons.
I have never heard of anyone applying peel-and-stick over hot mop and wonder what the advantage would be. Peel-and-stick is considered a longer-lasting system, so why put it over a material with a shorter lifespan? Also, I would make sure that the peel-and-stick manufacturer (as well as the local code official) approves this type of installation.
Hot mop is the traditional approach in Florida. It has a proven track record, but has a relatively short life span, is messy, and quality control may be inconsistent. It’s easy to repair, but should not be exposed for too long if there is storm damage the roofing.
Peel-and-stick generally has longer warranties, but is relatively new and not fully trusted by some Florida roofers. It does have a long track record in cold climates where it has been used successfully for a few decades, but mainly as protection at eaves and valleys rather than the whole roof surface. These older installations were mostly Grace Ice & Water Shield. In general, peel-and-stick can be exposed to the weather for longer – a plus if there is storm damage.
Many new peel-and-stick products have come on the market and, therefore, do not have an established track record. Also it is very difficult, if not impossible, to remove when reroofing. The choices are to leave the old underlayment in place or replace the roof sheathing. For that reason, some roofers place the peel-and-stick over a layer of adhered felt.
Bottom line: Peel-and-stick is a good alternative to hot mop and will probably last longer. It is less reliant on skilled labor and job-site variables. Choose a product that’s been around for a while and has a proven track record. With either hop mop or peel-and-stick, the installation is as important as the product. So choose a competent and trustworthy contractor.
Steven Do says
Best Underlayment for Tile Roofs in Hot Climates?
I am looking to replace the underlayment for our tile roof. We live in Phoenix, AZ. I have 4 estimates. Out of those, 3 roofers recommended TU-43 (either on 1 ply or 2 ply) and recommended Boral 40 (2 ply). The cheapest option is Boral 40. I am asking for your feedback regarding what the best option for Arizona climate. Thank you!
SBS-modified asphalt underlayments, such as the ones you mention, are a good choice for tile roofs. Two plies are, nor surprisingly, better than one and carry longer warranties — often twice as long.
SBS is a synthetic rubber, which gives the underlayment better strength and flexibility, and fairly good sealing around nails – though not a good as peel-and-stick underlayments. Synthetic underlayments, on the other hand, seal poorly around nail and staple penetrations, so are not recommended for tile.
The other big concern in your area is the ability to withstand high temperatures without softening or failing prematurely. TU 43 softens at 240°F, according to company literature. This compares favorably with “high-temperature” self-adhesive underlayments like Boral TileSeal HT, which are generally rated to tolerate temperatures up to about 250°F. I cannot find any temperature rating for Boral Ply-40, so would suggest contacting the manufacturer about acceptable service temperatures if you are considering this product
Standard #30 felt vs SBS-Modified Felt for Tile
Appreciate all of the wonderful information on here.
I am looking to install solar panels on my 20 year old 10 pound concrete tile roof. I was told by the solar company that the underlayment was cracking and that they needed it replaced prior to any work on panel installation.
The roofing company they contact with is suggesting a double layer of Fontana 30# felt.
I got a second quote advising instead to use APOC material. This company also said anything felt that’s not TU35 isn’t a good option for me.
The APOC is 30% more expensive than the quote I got for double layer Fontana 30# felt.
Would love to have some feedback on the direction to go in this case. So many choices…!
There are a lot of choices and a lot of opinions — but not a lot of data, which makes this a confusing topic.
I agree that a heavy-duty roofing felt made with synthetic-rubber (polymer) additives is much better than standard roofing felt (such as Fontana #30), which has deteriorated in quality over the years. Most of these products are use SBS polymers, but other types work just as well.
Examples pf SBS-modified underlayments include Fontana G40, Layfast TU35 or TU43, or a comparable APOC product. The polymer-modified materials are stronger, more flexible and tear-resistant, and generally longer lasting than standard asphalt felt. APOC states that they use “flexible rubber polymers,” in their underlayments, but do not identify the specific polymer used. Manufacturers’ warranties give you some idea of their level of confidence in a product’s performance and longevity.
All things being equal, a heavier underlayment is better than a lighter one and two overlapping layers are much better than one layer. There are minor differences from one manufacturer to another (and from one production batch to another), so I can’t recommend one brand over the others. However, it’s best to go with a brand that the contractor has used successfully for a long time and buys from a reliable local distributor who will stand behind the product. A good relationship between the contractor and distributor can help if there are problems.
It’s foolish to cut corners on the underlayment or flashing as these are almost always the first components to fail on a concrete or clay tile roof – and very costly to replace. Since most of the cost is labor, spending a little more on the materials is usually a good investment.
Michael Cordon says
Caveat – when using spray-foam insulation (SPF), whether open or closed cell) on the underside of the roof deck (think unvented or conditioned attic), using an air permeable underlayment is highly recommended!
Boral, the largest roofing manufacturer in US, strongly advises against using the vast majority of ice & water shield or “peel & stick” underlayments if the structure has SPF (or will have SPF in the future) on the underside of the roof deck.
The reason is that the roof deck (think the OSB, plywood, Zip, etc.) that’s atop of the roof rafters and below the roof tiles, needs to dry out from above because they don’t consider the roof deck being able to dry out from underneath if you use SPF. I know many believe that open cell SPF is air permeable … but Boral says it may not be. In AZ, I’m sure it’d be fine. But probably not in Houston in the long run.
My Houston roofing contractor was not aware of this potential issue – so I nearly made a potentially big mistake of having trapped moisture between two air & vapor impermeable surfaces.
The recommended solution by Boral and my SPF manufacturers was to use an air PERMEABLE roof underlayment so that my roof could dry out from above, specifically below the cement roof tiles. I used elevated battons (to get the roof dry ASAP as well as eave risers so my roof deck can breath a little.
For my underlayment, it was recommended that I use 2 layers of quality 30# felt that was installed in a staggered fashion – basically you rip the first 3’ layer of 30# paper in half after you mail down the bottom half of the paper with plastic caps. Then rip it in half (save it for next section of roof). Then use a full 3’ and hang it down even with the ripped piece at the metal drip edge. Then just keep going up the roof at 18” laps.
One additional comment, I heard that some folks are getting into trouble because they add SPF to their homes’ attic (underside of rafters) unaware that this may cause a moisture / mold issue later if their underlayment is air impermeable.
I hope this makes sense.
Michael Cordon, Esq.
All good points. In most cases, synthetic and modified-asphalt roofing underlayments are much less permeable than traditional asphalt felt. With spray-foam insulation, it’s best if the roof sheathing can dry upwards, so a synthetic underlayment is not a good choice (unless you use one of the few high-perm products). With tile or wood-shingle roofing, the sheathing can dry upward, especially if you enhance the breathability as you have done. However, with asphalt shingles or other impermeable roofing products, the roof structure cannot dry upwards regardless of the type of underlayment.
With roofing underlayments, manufacturers are much more concerned with stopping water penetration than with permeability. The assumption is that traditional roof ventilation will take care of any moisture problems. The equation is changed with spray foam. Moisture penetration from the household air leaking into the roof structure is virtually eliminated if the spray foam is applied properly. Water can still enter from above, however, through leakage at flashings, penetrations, damage, errors, or worn-out roofing.
You have a choice: either use a completely impermeable membrane such as peel-and-stick (and hope for the best), or use a breathable underlayment and install a breathable roofing system like you are doing. This is a belt-and-suspenders approach which is always a good idea with building construction where Murphy’s Law is always lurking. Few things are built or maintained perfectly in the real world.
Final point: If you do choose traditional organic felt, use a premium ASTM-rated product as asphalt felt quality (and thickness) has diminished over the years. Nowadays, unrated #30 felt typically ranges from 15 to 20 lbs. per square (100 sq.ft.) vs. about 27 lbs. for ASTM-rated material.
Do You Recommend Titanium Synthetic Underlayment For Tile Roofs?
We just had the S-tile on a 1231 sq ft single story home Mansard roof re-set as we are going to sell it and know it will be remodeled but a couple fell off and we felt it was a safety issue.
The roofer came highly recommended by a friend but used Titanium 50 underlayment right over the existing felt (house built in 1973 was probably original) I questioned that they could not see the condition of the wood underneath but they said as they hammer the Titanium 50 on they could tell if it was solid or not. What do you think?
We have a second 1231 sq ft single story down the street that has the same S-tile on it.
We want to replace those with Boral 900 series slate. This time I’d feel better if the old felt was removed . What underlayment would you recommend on a Mansard roof in California under this Boral tile.
Love your site. Thank you so much — I could not find any other site to help me like yours did.
First question: Can the roofing find damaged sheathing when hammering the new synthetic underlayment. Maybe, maybe not. If a large area was badly deteriorated and pulpy, yes, they should notice that. If there was a slow leak that had stained the sheathing, but it had not yet rotted, then no, they would have to see it.
As for what underlayment to use with Boral concrete roofing, consider that concrete roofs should last 50 or more years under optimal conditions. So most people want to use flashing and underlayment materials with a similar lifespan.
Whether to use synthetics or traditional felt underlayments is heavily debated among roofing experts. Many roofers are moving to synthetics, like the Titanium products (now owned by Owens Corning), mainly because they are easier and faster to install, less slippery to walk on, and more durable and wind resistant when left exposed for extended periods, as is the case on some projects.
How long they last is unknown at this point, but it’s reasonable to expect that the higher quality products will last as long as asphalt felt. Titanium carries a limited “lifetime” warranty against material defects with all the usual exclusion, including leaks at nail holes.
I personally like to see two layers of heavy-duty SBS-modified asphalt under tile. Boral makes a product called BoralPly 40, but there are several other good alternatives. On a mansard roof, with all the hips and changes of pitch, I would also consider a self-adhesive underlayment that seals around nails and penetrations. Boral makes several self-adhesive underlayments including GatorSeal, Citadel Plus, and HT for high-temperature installations (in case you are near Death Valley).
At the end of the day, the quality of the installation is at least as important as the specific product used. So make sure you go with a reputable firm with a strong track record in your area.
Dan Kam says
Does Modified Asphalt Underlayment Seal Round Nails?
Hi, I have S-clay tiles in San Diego, CA and I’m about to reroof a 30+ year old roof. I’m leaning towards Right Start UDL (Malarky Roofing Products) unless you have other recommendations. From previous comments, it sounds like I should use 2 layers of Right Start UDL, correct? A couple of roofers recommended 2 layers of 40# modified but I’m thinking Synthetic is the way to go. Is this product and other Synthentic Underlayments self sealing when they nail back in the clay tiles? I would think all Underlayments are self sealing to nails, but when I read comments on various websites, some installers think synthetics don’t seal up. What do you think? Regular slope on the roof on this 1980s built homes so I don’t think they are using battens nor have I seen any use of them on other reroofs.
Yes, a double layer (two-ply) installation of a heavy modified asphalt underlayment is a good approach for tile roofs. These “modified” asphalt underlayments add synthetic rubber polymers to give the asphalt greater strength, durability, and flexibility. Most use a polymer called SBS, but others use proprietary formulations including Malarky Right Start UDL, which uses proprietary mix of synthetic rubber and recycled rubber and plastic.
Since there are no national standards for these products, you are relying on each manufacturer’s performance claims, backed up by testing, field performance, and warranties to determine how a product will perform. As a class of products, they have established a good track record, but it is difficult to compare one to another. Some claim they seal around nail penetrations. Others do not, but will tell you that leakage at nail penetrations is negligible.
For complete protection at nail penetrations, you typically need to use a self-adhesive membrane, often called Ice & Water Shield, the original product from Grace. These membranes offer great protection at valleys, eaves, and transitions, and around skylights and other openings.
The term “synthetic” underlayment usually refers to lightweight plastic fabrics woven or spun from polyethylene or polypropylene. They may have more than one layer as well as a non-slip walking surface. They are similar in composition to plastic housewrap. Roofers like these because they are easy to install and many offer a good walkability on steep pitches. But, like modified asphalt, national standards are lacking and the product is endless. I would consider these on an asphalt roof, but at this time would not recommend these for a tile roof.
Dan Karn says
Thanks Steve for the quick response!
I called the supply house my roofer wanted to use, and they didn’t carry that Right Start or it least it wasn’t in stock. They did carry the Owens Titanium UDL50 synthetic. Do you have any experience with that product? Should I be using 2 layers with my clay S-tiles if I go that route?
I’ve used the lighter weight Titanium underlayment on an asphalt shingle roof, but never used this version. Owens Corning Titanium is considered one of the premium (and more expensive) synthetic underlayments and this is their heaviest grade, which they do recommend for tile, metal, and other premium roofs.
Many roofers like the synthetics because they go down quickly without wrinkles or bubbles and are much lighter than asphalt. UDL 50 weighs under 5 lbs. per square (100 sq. ft.) compared to about 40 pounds for the heavy-grade modified asphalt products. They also include a good, non-skid walking surface that makes installations go more quickly with less staging.
Some roofers love synthetics for these reasons, but some prefer traditional felt (or modified felt) and feel that it is more waterproof at penetrations and laps. Capped nails are best with synthetics, but capped staples seem to work with some. Because every synthetic is different, it’s hard to generalize. Once the roofing is installed, leakage of the underlayment is not an issue — unless there is a roofing leak. Due to their design, tile roofs are more prone to leakage than other roofing types.
And, yes, two layers of underlayment is better than one. It’s also true that the workmanship and experience is usually more important than the specific product used. You generally want a product that your contractor has used a lot and has confidence in.
Synthetic underlayment would not my first choice for a tile roof because of the greater potential for leakage at nails/staples. But the specs and test data for Titanium look promising. If you want a roofer’s view of the issue, you might find this link of interest.
Can Black Tar Drip From Underlayment?
We are living in a 1925 Spanish house in Los Angeles County.
Our Living Room has a 17 foot tall wooden beam ceiling.
There is no attic.
As you can imagine, the terra-cotta clay tile on top of that roof heats up during the day and is baking our living room like an oven.
Since we had a couple of leaks in the last rain and had to fix them anyway, we decided to re-do the entire living room roof (except one portion that butts up to a flat roof above our upstairs office) and add insulation, so we can save on utilities.
Our contractor suggested 2 layers of Fontana # 40 lb underlayment and 2 layers of low-e insulation.
We had the work done August 2019 and were very happy with the outcome. The room feels much cooler now.
We don’t have to use the A/C as much as we used to.
Last week it got very hot and I noticed some dark spots on the floor. I thought our dog might have been dragging something into the house and cleaned it up. Then we had spots again…….and I noticed that it is a tar-like substance dripping from the ceiling.
We had our Contractor and the Roofer over to take a look so we can stop getting stains on our Persian rugs.
They are telling us that what they used was not a torch down product, it is nailed in place and they don’t think what they used will just ‘melt’.
They think that it might be something coming from the flat roof on the other side of the pitch. But we had that roof done 13 years ago and never had a problem. Is it possible that a 13 year old asphalt roofing material all of a sudden starts to melt? The tar-like leak is only about 1 ceiling board from the top of the roof where they installed new cap tile with the fontana roofing underlayment underneath.
I have done some research on Fontana underlayment paper and can not find a Fontana #40 lb. version. There is a #30 version and the specs say that it is ‘asphalt saturated’. So I guess even if it was not torched down – there is a tar-like substance. I just don’t know if that would start to melt all of a sudden under the tile – even if the tile gets very hot (probably 135 degrees on top of the roof).
We would appreciate your opinion very much to solve this mystery!
Fontana makes a 40 lb. product called VulcaSeal G40, which may be the underlayment used on your house. This is one of a number SBS-modified-asphalt underlayments widely used tile roofs. These products typically use a fiberglass matt saturated with asphalt that has been modified with a synthetic rubber compound and other additives.
The rubber compounds improve the material’s strength, toughness, and elasticity. They also improve performance in low and high temperatures. Other chemicals may be added as well for improved performance in specific applications.
I have heard of asphalt underlayments failing prematurely in extreme heat or from UV exposure, but not dripping or oozing asphalt.
However, melting asphalt can be a problem with peel-and-stick membranes. Some of these are formulated for high-temperature applications, but the standard products can begin to soften and flow when temperatures reach 120 – 180°F, depending on the specific formulation. Some high-temperature formulations are rated for temperatures above 200°F.
Contact with other types of sealants or with soft vinyl can also cause the material to soften and flow. In general, butyl-based flashing membranes are more stable and heat-resistant than the more common (and less expensive) modified-asphalt products.
Peel-and-stick flashing membranes are commonly used on roofs for sealing around skylights and other openings, chimneys, transitions, valleys, and other tricky spots prone to leakage. So that’s the first place I would look as a source for your problem.
It’s also possible that the roofers used an asphalt-based roofing sealant to seal an area above the leaking tar. These are sometimes used as a quick-and-dirty way seal a leak, but are less common on new roofs or re-roofing jobs. There are many formulations, but most don’t have a very long service life.
If the problem persists, you may need to remove some tiles in the area of the drip to get a better look. I would also ask the roofer about the transition between the new roof and the existing flat roof. What did they use to seal this transition? Openings, transitions, flashings, and similar changes in materials or slope are the places where roofs are prone to leakage and other problems.
Should I Seal Between Roof Tiles With Silicone?
The cement tiles along my roof edge were not nailed properly so I glued the lower end of each tile to the ones below with silicone caulk about 12 years ago. The caulk bonded well and is still in good condition.
Now I am thinking of sealing the rest of the cement tile roof with silicone caulk to insure that no water can get under the tile. I will seal the bottom edge so wind cannot blow water up under the tile and through gaps between the tile. I have a lot of experience using caulk guns. Silicone caulk lasts a long time even when exposed to the elements. What do you think? Thanks, Dudley
Sounds like your quick-fix with silicone did the trick for the edge tiles, but I’m not sure you want to use this on the rest of the roof. The lower roof edge is exposed to the greatest wind load, so you probably improved the durability of your roof with the silicone sealant, which acts as both a water-seal and adhesive. Although silicone is not traditionally used to seal or secure roofing tiles, it should work OK as long as you get a good bond – so always test first.
Most silicone caulks are acid-cure and have a vinegar-like smell. These adhere well to shiny surfaces like glass, tile, and some metals. Neutral-cure silicone stick better to most metals and more porous materials, so this may be a better bet for concrete. Whatever sealant you choose, it’s always a good idea to test first before doing a large area. Also read the instructions regarding cleanup and the need for primers with certain materials.
With tile roofs, the underlayment is considered the primary waterproofing layer. So assuming that you have a good underlayment, you do no need to caulk every joint and gap in the roof tiles. If you are in an area subject to windblown rain and are finding evidence of roof leakage, then caulking could be a temporary fix until you can remove the tiles, and replace or repair the flashings and underlayment as needed.
If your main goal is to secure the tiles better in high winds, then you would be better off using a tile adhesive to bond the tiles each other and the roof deck or purlins. You may be able to do this without removing the tiles if they are loose enough to lift a bit. In this case, you should be using a roof-tile adhesive such as OSI RT-600 or a low-rise foam adhesive such as Dow Tile Bond Roof Adhesive. This is a one-part adhesive available in 23 lb. tank kits with a hose and nozzle, ideally suited for this type of work. (Two-component foams are best left to professional applicators).
You would need to experiment to see how well you could apply the adhesive to tiles already in place. Also have the correct solvent at hand for cleanup.
As with the silicone, I would consider this temporary fix until it is time to re-roof. The flashings and underlayments often fail long before the tile, so if your underlayment is in good shape, you could get several years out of you repair. Best of luck!
VulcaSeal SBS vs Malarky SBS
I have two quotes to reroof our house. One quote using Vulca Seal G-40 tile underlayment and the other quotes Malarky 350 SBS modified underlayment. Neither quotes whether it is one or two layers. Which is the better produce please?
There are literally hundreds of underlayment products on the market now and it is not possible to keep up with every one. I am familiar with VulcaSeal G-40. I would recommend a double layer, which has a 20-year warranty vs. 10 years for a single layer. See produce details for VulcaSeal G-40 Fiberglass SBS-Modified.
Malarky 350 SBS is a very similar product, that is, an SBS-modified asphalt underlayment on a fiberglass mat. Assuming that the product they are using is Malarky 350 Paragon Chroma Cap, the main difference is that it is surfaced with mineral granules, so it can be used as the top layer of a built-up roof. The granular surface protects the membrane from UV, weather, and occasional foot traffic.
I’m not sure how the granular surface would help as an underlayment. However, the product is sometimes used for that purpose. As an underlayment, it is generally installed as a single layer and mechanically fastened. The warranty varies with the application, so I would get more details from the contractor about installation and warranty. See product details for Malarky 350 Paragon Chroma Cap.
I would be happier with a double layer of SBS-modified, when going under tile, which you can expect to last for several decades. The flashing and underlayment are typically the first elements to fail on a tile roof.
You are correct. The standard approach to two-ply roofing underlayment is to lap a 36-inch roll by 19 inches, providing two plies across the entire roof, plus a 1-inch “headlap” (3-ply coverage at the top of the lap), as shown in the illustration. By comparison, the standard overlap for single-ply underlayment is only 2 inches at horizontal laps and 4 inches at vertical laps.\
I’m not sure why this contractor installs underlayment the way he is describing and don’t know how it would perform compared to the industry-standard installation, as shown below.
Regardless, you are correct that you are risking warranty problems if the installer does not follow industry standards and especially instructions provided by the manufacturer.
So definitely bring this up, and unless the contractor has a compelling reason to not follow the standard procedure, insist that he do so. Or find another contractor if necessary.
Single Vs. Double Layer for Roofing Underlayment?
We are needing to reroof a seven year old house due to the use (misuse) of a synthetic underlay ( no battens used so every tile was nailed through the underlay resulting in 1000’s of holes). We have narrowed the proposals to two. One is quoting a single layer of of the Tu-43 and the other is proposing two layers of Right Start UDL. Are the two products comparable to each other (and thus two layers would be the better option)? Is there anything else specifically I should be looking at in these proposals (ie anything specifically they should be doing at valleys, vents, etc?)
Sorry to hear about the need to reroof after just seven years. Was the roof leaking? In what part of the country are you located? Also, were you able to reuse your roof tiles?
Right Start UDL and TU-43 both use fiberglass mats impregnated with SBS-modified asphalt, sometimes called “rubberized” asphalt. TU-43 is slightly heavier (43 lbs. vs. 40 lbs. per 100 square feet). Each company has its own proprietary formula, but both are premium products with a good track record.
Two layers of underlayment is definitely superior to one. You have a second layer of defense, in case there are problems with the first. For example, here is the chart for Layfast warranties:
10 year: One layer TU35
15 year: One layer TU43
20 year: Two layers TU35
30 year: Two layers TU43 or one layer TU70
Of course, it’s important that the installer follow the manufacturer’s installation instructions, paying special attention to fasteners, overlaps, and offsetting vertical joints. This is shown in the manufacturer’s instructions for UDL Right Start. Low-slope roofs, less than 4:12 pitch require special installation.
Finally, pay close attention to any valleys, vents, skylights, and other penetrations and transitions. The best product at valleys is self-adhesive underlayment, which self-seals around any nail hole or other penetration. This is also recommended around skylights and other transitions. If you live in a snow region, a 36”-wide strip of this material – sometimes called Ice & Water Shield – should go along the eaves.
Read more on Double Layer Roofing Underlayment
Thank you so much for responding. It is so difficult to compare apples to apples so to speak.
Yes, our roof was leaking, in at least 3 locations that we have noticed (and while we COULD repair, there was the unknown factor of other unseen or future leaks). We are located in Phoenix, Arizona.
The installer of the Right Start does a 15 inch overlap (so honestly I’m not sure if he’s using that to say that he is using essentially two layers). Both installers had stated that the products do self seal around nail holes. Is this not the case?
The installer for the TU-43 stated that the underlay would be installed up wall/curb (of walls, skylights and fireplaces) with a rubber base and seal).
And from your response to the initial post, it looks like I need to also determine what type of flashing they will be using?
Thank you again for your help
Most roofing underlayments are 36 in. wide, the material needs to be overlapped a minimum of 19 in to achieve full double-coverage. That’s half the width of the roll plus one inch for “headlap”. Headlap is the amount of lap over the top of the course two below. Since Right Start UDL comes in wider rolls (a bit over 39 in.) then the installer would need to overlap by 20-1/2 in. for double coverage.
both these products will provide better sealing around nail penetrations than standard roofing felt. However they do not provide the same level of protection that you would get with a self-adhesive flashing membrane.
Finally it is good to know what type of flashing they are using as the flashing is often the weak link in a long-lasting roofing system such as tile. The best quality flashing metals are expensive, but so is removing the roofing to replace failed flashings.
Read more on Flashing Metals
Lawrence Stavosky says
Should I Use Peel-And-Stick Underlayment for Tile Roof?
I am having a house built in the Sacramento area and my builder and roofing contractor both swear by going with two layers of felt ,.for a concrete tile roof. While that sounds OK. both subs who are bidding on this want $2500 -$3500 more to double the Felt. I can also get a peel and stick membrane but that will be about$6600. Any Thought besides moving from Calif.
Two layers of ASTM-rated asphalt felt is good substrate for tile, but for a little more money you can get two layers of SBS-modified felt, which will most likely last longer (which you’ll find out if you’re still there in 20 to 30 years).
These are products like VulcaSeal G40 (Fontana), Layfast SBS T35/43 (MB Technology), or Right Start UDL (Malarky Roofing Products) that are discussed in this article.
I think that peel-and-stick is overkill for your area, which gets only a modest amount of rain. However, it’s always a good idea to use peel-and-stick at any valleys, around openings such as skylights, and at any tricky transitions. These are the areas where the vast majority of leaks occur.
You do live in one of the most expensive building markets in the US. Although, New England, where I live is not much better.
Best of luck with your new roof!
Holly SC says
Best Underlayment for Tiles in Hot Climate?
I live in Las Vegas,NV and this year has had a lot of rain ( for a hot dry climate). Leaks have necessitated a full re-roofing but I am getting different opinions from roofing contractors on the underlayment. One said go synthetic and another said not with cement tiles. One said a single layer of 30 lbs is good and a second said double layer would be thousands more $$. What is the best underlayment for Las Vegas and is it worth getting 2 layer of 30 weight or 1 layer of 40 or 50 weight.
Two layers of ASTM 30-lb. felt is the minimum you should use on a tile roof. An upgrade to consider would be two layers of 35- to 40-lb. SBS-modified asphalt underlayment. There are many good sbs-modified underlayments on the market. I am most familiar with VulcaSeal G40 (Fontana), Layfast SBS T35/43 (MB Technology), or Right Start UDL (Malarky Roofing Products). These offer greater strength and durability than standard felt and should provide a longer service life. For roofing valleys, skylight flashing, and other areas prone to leakage a peel-and-stick membrane is the best choice. These have very aggressive adhesives and self-seal around nails and other penetrations.
Since you are in a very hot climate, you would want an underlayment rated for high-temperature applications.
As for synthetics, there are many on the market, so it is difficult to say which would be suitable for tile. In general, synthetics are thinner and lighter than asphalt products, making them easy to install – a benefit for installers, but not necessarily for homeowners. Most are non-woven fabrics, similar to plastic housewraps the Tyvek or Typar you see on sidewalls. How well that last over time in a very hot climate is anyone’s guess. There are currently no industry standards for these materials.
In general, two layers of underlayment offer better protection than one heavy layer. Two layers of any underlayment should not cost “thousands” more than one layer. Most of the premium underlayments described above range in price from 20 to 40 cents per square foot, plus labor of maybe 30 cents per square foot (for each layer). Total cost for two layers could be a little over $1 per square foot, but the cost to rip off the roof tiles to repair a failed underlayment is far greater.
Frank D. says
Will Rain and UV Harm Exposed Underlayment?
We are having a new tile roof installed in s. Florida. After the first layer of underlayment was installed, we had three days of back-to-back rain resulting in a leak within the house. Not sure if this is due to water penetration from a weak spot; but will have the roofer verify. Our bigger concern is whether or not the first membrane (specified as 30# ASTM D-226) is totally compromised after getting drenched. Also, how long will the membrane need to get fully dried before the next layer is applied? How long can it be exposed to UV? Thanks for your input.
Organic roofing felt, like you are using, does not have any published exposure limit, but the rule-of-thumb is 30 days and it should be completely dry before roofing. Technical reps at underlayment manufacturers such as Tamko will generally tell you that organic felt paper should be covered as soon as possible.
All underlayments start to deteriorate from UV exposure as soon as they are installed. The longer it sits exposed to sunlight and heat, the shorter its overall lifespan. So hot regions with intense, bright sun like the Southwest would have the greatest risk of deterioration.
The rule-of-thumb in the industry is no more than 30 days exposure for organic felt. But this is just a rough guide and will vary with climate and the quality and thickness of the felt. ASTM 30# felt is going to fare better than generic 30-lb. felt that does not meet ASTM standards. And 30 lb. is much better than 15 lb.
Cheaper non-ASTM felt is lighter and more prone to absorb water. Non ASTM #30 felt can weigh as little as 20 lbs. (per 100 sq. ft.) vs. 26 -27 lbs. for ASTM #30 D-226 (also called Type 2).
All felt paper is water-resistant, not waterproof. While moderate water exposure will not harm felt, it can cause wrinkling or bubbling, especially in cheaper and lighter felts. This can cause problems with tearing, sealing at laps, and telegraphing though shingles. With any roofing type, the asphalt underlayment should be completely dry before installing the roofing or another layer of underlayment. Usually that means a few days of sunlight, but it will vary with conditions.
You should definitely have the leak checked out and repaired. With a tile roof, you want the underlayment to be completely waterproof as the tiles will allow some water penetration from windblown rain.
Best of luck with your new roof.!
Hal Stevens says
What Underlayment Is Best For Reroofing Tile?
I have two roof estimates for underlayment replacement of the entire tile roof, which at this time has the builder’s original paper from 1989 when I purchased the house new. Two different underlayment suggestions, very confusing: 1) Re-felt with 2 layers of SBS #40 lb. roof felt, 2) Nail 2 layers TU 35 or Malarkey Modified sheets. What is the difference? Which would be best for longer life expectancy?
With all the choices today in roofing underlayments, it’s easy to get confused. Experts still debate which is the best approach.
All of the products you mentioned are essentially the same thing: asphalt-based underlayments modified with SBS, which is a type of synthetic rubber that gives the material greater strength and durability. These underlayments also self-seal to some extent around nail penetrations, but not to the same degree as peel-and-stick membranes, discussed below.
Roofing felt modified by SBS or APP, another synthetic rubber, are an upgrade from traditional asphalt felt and should provide a longer lifespan. Exactly how long is difficult to predict. Warranties for two layers of SBS-modified asphalt underlayments range from 10 to 30 years.
Just to be clear, “SBS #40” is not a brand, but indicates an SBS-modified underlayment that weighs 40 lbs. per square, roofing jargon for 100 sq. ft. of roof area.
Two layers of 35 t0 45 lb. SBS-modified felt is considered a good base layer for tile roofing. The differences from one product to another, among name-brands, are small and difficult to evaluate as each company uses proprietary methods and additives. Also each company offers different options for weight, the top surface material, and the “mat” which reinforces the underlayment. The mat can be felt, fiberglass, polyester, or other synthetics.
In general, heavier is better than lighter. Two layers are better than one. Product warranties offer some indication of how much confidence the manufacturer has in the particular underlayment, but roofing warranties aren’t worth much in practice as they are usually pro-rated and do not cover labor. (And many roofing manufacturers have a history of weaseling out of warranty claims by nitpicking about product installation.)
An upgrade from two layers of SBS-modified is a single layer of a heavy self-adhesive membrane, which seals better around nails and other penetrations. Self-adhesive (peel-and-stick) membrane is probably overkill in a dry climate, but worth considering on low-slope roofs, in wet climates, and in cold climates with snow buildup. The main downside is that the aggressively sticky material is very difficult to remove when re-roofing.
In very hot climates, special high-temperature underlayments are recommended. You can check with the contractor or manufacturer about temperature limits for a particular underlayment.
Renee Vargas says
Every Seen Tile Roof With No Underlayment?
I’m in Northern CA looking into purchasing a home built in 1982. The roof is clay tile. It does not have any underlayment, it has skip sheathing. (No plywood or roofing paper). Is this common? I’ve never seen a tile roof with no plywood under it. I’m rethinking the price of the home.
Installing clay or concrete tile over skip sheathing, with no underlayment, is certainly not in compliance with modern building codes and current practice. Nowadays, the tiles are always installed over solid sheathing with one or two layers of underlayment.
Omitting the underlayment was a fairly common in some parts of California in the 1970s and 1980s. Some people claimed it was a better roof because the tiles had to be installed more carefully to prevent leaks – but that logic seems pretty flimsy. I think it was mainly done to save the contractor a little money, or maybe in the mistaken belief that a roof must “breath”.
Whatever the reason, it was a bad idea, because eventually tiles crack and flashings rust out, leading to leakage. Matching old tiles is difficult unless the owners kept a good supply in the basement.
If all the tiles are intact and there are no signs of leakage on any of the ceilings, you might get lucky (or they may have done a good job with BIN or another stain-blocking primer). If you’re not so lucky, you may need to replace the roof now or within a few years.
So I would definitely factor the cost of a new roof into your offer. While it is possible to remove the old tiles, add sheathing and underlayment, and then replace them, most people go with new tiles unless the existing ones are relatively new and in excellent condition.
Steve Jeffers says
How Long Can Underlayment Be Exposed?
I have a home being built in central FL which will eventually have a concrete tile roof. My concern is the underlayment has been on the roof more then a month, but the tiles have not been installed. Is the underlayment made to withstand the harsh FL weather for that long a timeframe or should I expect trouble down the road? Thanks for any help.
The allowable exposure time to UV and weather varies depending on the specific underlayment used. All underlayment products begin to deteriorate the moment they are exposed to sunlight. The rule-of-thumb generally followed in the industry is that asphalt-impregnated (organic) roofing felts should be covered within 30 days.
At one end of the spectrum are some high-end synthetic underlayments, which publish exposure limits of 3 to 12 months depending on the membrane material and the surface coating. A mineral-coated cap sheet, which can be used for underlayment or the final roof covering, can be exposed for a year or more.
SBS-modified membranes, commonly used today, are typically rated for 1-3 months of exposure. Most of the self-adhesive underlayments, such as Grace Ice & Water Shield, have a maximum exposure time of 90 days.
Once you have identified the type of underlayment used, you can look up the product’s technical specs online. If you cannot find a published number for exposure to weather, contact the manufacturers’ technical support staff by phone.
Most technical reps I have spoken with recommend getting any underlayment covered as soon as possible, despite the “maximum” allowable time. They stress that the longer the exposure, the greater the damage to the underlayment. The longevity of the product could be compromised.
Some companies do not publish any number because they believe that the underlayment should be covered as soon as possible and don’t want the liability associated with extended exposure to the elements.
Karl Fendt says
Tile Roof Underlayment For Hot Climate
I live south of Tucson AZ and after 10 years I need a new roof like about 300 other houses in this community I had three different roofing companies to inspect the roof and two gave me a price for Underlayment Roof Felt #40 and one offered MAT40 from Bitec and was also $2000 cheaper, what do you think of this product here in the Sonoran desert
thank you for your time
MAT40 is a peel-and-stick rubberized asphalt membrane, similar to Grace Ice & Water Shield. Based on its specs, it appears to be a high-quality, heavy-duty membrane flashing suitable for high-temperature applications. The “40” stands for 40 pounds per 100 sq. ft.
In general, these membranes seal around nails and other penetrations, which is why they are widely used for valleys, skylights, eaves (for ice dams in cold climates), and other roofing details prone to leakage.
Using them for the entire roofing surface is a fairly new concept but gaining in popularity. The only real downside is that removing them is difficult, if not impossible, when re-roofing, so you may need to tear off and replace the roof sheathing at that time, a potentially expensive proposition. Depending on its condition, it may be possible to add a new layer on top, leaving the existing sheathing in place.
You can read the specs on MAT40 at this link. It’s definitely a superior product to standard 30-pound roofing felt.
Another good option is two layers of a 4-pound modified-bitumen underlayment such as Bitec ULD 40 (read specs). Similar products include Layfast SBS T35/43 (MB Technology) and Right Start UDL (Malarky Roofing Products). Before using any of these products, I would recommend checking with the manufacturer about high-temperature applications as roof temperatures in your area can exceed 150 degrees F on the roofing surface and possibly hotter underneath.
These seal fairly well around nail holes, but not as well as peel-and-stick underlayments. A double layer should have a similar lifespan to a peel-and-stick membrane, but predicting actual performance in the field is difficult as there are many variables. Length of warranty is one indicator, although warranties on roofing products are not all that valuable. They are usually pro-rated for time used and do not cover labor – and that’s assuming that the company is still in business and does not try to weasel out by claiming that the installer did not follow installation instructions perfectly.
Peel-and-Stick Underlayment for Saddles & Crickets?
I moved into a new house seven years ago and just discovered that the roof has a potential building code defect. The concrete tile roof has two saddle structures that are made of rolled peel-and-stick roofing. Otherwise the roof is concrete tile.
I found the local building codes for crickets and saddles are quoted as: Cricket or Saddle coverings shall be of sheet metal of the same material as the roof covering.
My question is: what is the legal definition of “roof covering” as I have had roofing contractors tell me that the roof covering is in fact the underlayment material and not the concrete shingles. Any light you could shine on this subject would be appreciated.
I live in Nipomo, CA, in the county of San Luis Obispo.
Peel-and-stick underlayments can make a good watertight, protective barrier for details such as crickets and saddles, but are not intended to be left as the finish roofing material. Most underlayments and flashing membranes will deteriorate from long-term exposure to sunlight. UV ratings typically range from 30 to 120 days depending on the product. If they used a finish roofing membrane such as EPDM on the saddles, then it would provide long-term protection.
What is accepted by code in your area is another question. Building codes are written at the national, state, and local level, and, like all laws, they are subject to interpretation. The person who interprets the code is your local building inspector. So, as a practical matter, the best way to answer this type of question is to contact your local department of building inspection.
In my experience, the term “roof covering” always refers to the finish roofing material – tile, shingle, slate, metal, EPDM – not the underlayment. Not sure why the roofing contractors are telling you otherwise. However, building practices and terminology can vary a great deal from one area to another.
For example, maybe it is standard practice in your area to use some form of membrane roofing for crickets and saddles. Although this may be inconsistent with the written code, the local building department may accept this as an alternative that meets the requirements of the current code.
Best Replacement Underlayment for Concrete Tiles
I want to replace the Underlayment of a 35 year old concrete tile roof. Half of the roof has an attic and the other half has cathedral ceilings. I’ve got three solar tubes and want to add three more. Which of the following options offered by roofing contractors will be the most cost-effective:
Add Boral elevated batten system?
Add O’Hagin cloaked attic vents?
I’ve gotten 4 bids that list different materials. It sounds like two layers of malarkey UDL SBS 40# Underlayment will be more leakproof than a single 78# modified granular surface felt Underlayment. I’m in Southern California, Zone 6. Our weather is getting hotter and more similar to the adjacent zone 9. My understanding is that California building codes require using an elevated batten system for zones 10-15.
Two layers of Malarkey UDL SBS #40 underlayment, or similar products from Layfast or MB Technologies, should offer better protection and a longer life span than a single layer of granular surface underlayment.
Regarding your other questions, it is difficult to say which approach is best. I like the Boral elevated batten system as it provides three benefits:
• Lets water drain out, prolonging the life of the battens and underlayment — more of an issue in rainy climates.
• Eliminates most nail holes through the underlayment.
• Increases airflow between the tiles and roof sheathing, which could reduce cooling loads by a modest degree.
will prolong the life of the battens and underlayment by allowing any trapped water to easily drain down the roof – and water will definitely penetrate concrete and clay tiles. In an arid climate like your, however, this may not be a big concern.
The same effect can be achieved with “counter-battens” that run vertically up the roof below the horizontal battens. For the ventilation to be effective, however, you would either need a tile profile that vents naturally or eaves and ridge vents designed to work with your type of tile.
The O’Hagan system provides an inconspicuous way to add balanced (low and high) vents to a tile roof. These install in the field of the tile rather than at the soffit and ridge, and blend in with the tile profile. They can be used to ventilate the attic area, but would not be a good choice for most cathedral ceilings, since you would need a high and low vent for every joist bay.
Venting cathedral ceilings is always tricky and research shows that air movement up the typical narrow ventilation space is pretty minimal. Nonetheless ventilation here is often required by code and can certainly help an area dry out if there is ever a roof leak. It can also have a modest effect on cooling loads. Whether you insulate above the sheathing with raised battens or below the sheathing (but above the insulation) with soffit and ridge vents, the effect should be similar. Either option should work fine.
Amil rocha says
Will Underlayment Protect Roof When Tiles Blow Off?
Hi,I have a tile roof on a new home in Naples Florida. However, with the current Hurricane Irma, I lost a couple of tiles in the corner of a lower roof, not my main roof. My question is will the underpayment protect the house from leaks until I can get it repaired?
Tile roofs are not 100% waterproof, especially on low-sloped roofs with windblown rain, as you get in Florida. So the underlayment for tile roofs is designed to be waterproof.
Assuming that the underlayment was installed properly and was not damaged, you should be OK with a couple of missing tiles. You may have some minimal leakage at nail holes if nails were pulled out, but not enough to cause damage. If the underlayment is exposed to sunlight for more than a few weeks, it may start to deteriorate – depending on the material used.
Some underlayments perform better than others, last longer, are more UV-resistant, and seal better around nails. The traditional approach in Florida has been a 30-pound felt “base sheet” nailed to the deck, and with 90-pound roll roofing (cap sheet) hot-mopped on top. This formed a very durable, heavy-duty underlayment that sealed well. However, after 20 years or so in the heat, the 30-90 hot mop system was prone to cracking and failure.
The current trend in many parts of Florida is SA (self-adhesive) membranes and synthetic membranes, of which there are many. Self-adhesive membranes self-seal around nail penetrations and offer the best protection. The downside is that they are nearly impossible to remove when re-roofing. It is hard to generalize about the synthetics since they are fairly new do not yet have well-established manufacturing or code standards. If you can find out what was used, I’d suggest contacting the underlayment manufacturer to get their recommendations.
Cost to Replace Tile Roof Underlayment
How much does it cost to replace the underlay for a tile roof?
If most of the tiles are in good condition, then a “lift and relay” job might make sense — although the savings are less than you might think. There are a lot of variables — type and age of tiles, the attachment system, access and pitch of roof, complexity of the roof, and the quality of the new flashing and underlayment system. Also, a certain number of tiles will be damaged when they are removed and matching the existing tile can be difficult. In general, clay tile is a lot more costly than concrete tile. Local labor rates also play a role.
That said, you can usually save money by salvaging the existing tiles. To remove and replace the tiles with new flashing, underlayment, and battens, you can expect to spend from $300 to $700 per square (100 sq. ft.). A new tile roof, on the other hand, will typically range from $400 to $600 per square for concrete tile, and $700 to $1,000 per square for clay tile, plus the cost to remove and dispose of the existing roof which can add another $100 to $150 per square.
Whether you are relaying the existing tiles or buying new ones, don’t skimp on the flashing and underlayment, which are the main waterproofing layer. A double layer of 40-pound ASTM-rated felt or fiberglass membrane is a good idea.
Of course, the only price that matters is the one you get from a contractor. Get at least three bids and compare specs, prices, and warranties, and call references. Some companies will not warranty a “life and relay” job. You can find a lot of variation in roofing bids for the same basic job. Best of luck with your new roof!
New Underlayment Over Old?
Can new tile underlayment be installed over old underlayment or should the old be removed first? What are the pros and cons?
As a practical matter, most roofers want to strip down to a clean surface before reroofing, and some roofing manufacturers require this — and in some cases require that you use a specific underlayment (one made by them, not surprisingly).
Stripping the roof allows you to find areas of damaged sheathing, flashing problems, or any other conditions that might interfere with the new work.
In specific situations where the underlayment is in good condition and very difficult to remove — for example, self-adhesive Ice & Water Shield along the eaves, I would consider leaving it in place and covering with a new layer of membrane as long as the level change in the underlayment would not show through the new roofing material. With a tile roof, this should not be a problem.
Sandra Quilty says
Best Underlayment for Tile Roof
Our roofer has provided specs for the underlayment of a terra cotta tile roof that confuse us.
The initial proposal calls for MBTechnology Modified-SBS Supercap fire-rated underlayment for high-fire zones with double layers only in the roof valleys. (Note: We’re in southern california and not in a high-fire zone).
He then offers, evidently as alternatives, TU 70 with a 10-year limited warranty on materials or two layers of TU 35 with a 20-year limited materials warranty. Could you offer a recommendation or enough info for us to make a decision?
Of the options offered by your roofer, a double layer of Layfast TU35 is your best choice. For just a little extra money, you could upgrade to a double layer of the heavier TU43, which now comes with a 30-year warranty, according to the manufacturer, MBTechnology. They just started offering the 30-year warranty, the longest in the industry for an SBS-modified underlayment.
By comparison, a single layer of SBS-modified Supercap is warrantied for only 10 years. Supercap is mineral-surfaced product mainly used as the surface (cap) layer for two-ply roll roofing. It’s main appeal as an underlayment is that it can be exposed to the weather for extended periods due to its mineral surface. However, this should not be an issue with a normal construction schedule.
For the valleys, the best product is a self-adhesive “ice and water” membrane that self-seals around nails and other penetrations. Most underlayment manufacturers sell a version of this product. MBTechnology calls theirs Ice & Moisture Block SBS. Grace Ice & Water Shield, now sold by GCP Applied Technologies, was the first such product on the market, introduced almost 40 years ago, and is probably the best known peel-and-stick roofing membrane.
In addition to valleys, self-adhesive membranes are also useful around skylights, eaves, and roof transitions such as roof-wall intersections. They help protect against wind-blown rain and ice dams in freezing climates – not a problem in Southern Cal.
Best of luck with your new roof!
G40 vs. 30-Pound Felt
Hi, I am comparing quotes for replacing the underlayment of my concrete shake roof in Los Angeles. What is the price difference between two layers of G40 and regular 30-pound felt. ( I have a total roof area of 3700 sq. ft.) How long would two layers of G-40 last compared to two layers of 30-pound felt for a Los Angeles home? Would you recommend two layers of G40 or 30 lbs felt ? Thank you !
The weak link in tile roofs is the underlayment and metal flashings, which often fail before the tiles. Tiles can last 50 years or more, but underlayments often fail in 20 to 30 years.
Fontana VulcaSeal G40 underlayment is definitely a better product than “regular” 30-pound felt because it is manufactured to ASTM standards, and is much heavier. ASTM 30-pound felt can weigh as little as 26 pounds per square, while standard #30 felt can weight as little as 15-20 pounds. Also G40 uses a fiberglass base and SBS-modified asphalt, which make it more flexible and durable than standard asphalt-felt underlayments. SBS is synthetic rubber, which gives the asphalt greater elasticity and seals better around nails, although these products are not technically self-sealing.
Similar SBS-modified underlayments with fiberglass mats are made by Malarky (Right-Start UDL), a 40-pound product, and Layfast SBS TU35/43, which comes in two weights – 37 and 43 pounds. All things being equal, a heavier underlayment can be expected to last longer.
Predicting how long any roofing product will last is a tricky business and is a function of the material, installation method, and climate. The roof color and slope also play a role, as does the maintenance of the roof. Cracked tiles and the build-up of organic debris can also shorten the life of the tile and underlayment.
G40 and Layfast SBS both offer 20-year warranties for two-layer installations, while Malarky offers a 10-year warranty. MB Technologies just started offering a 30-year warranty on their TU43 underlayment. It is reasonable to expect 30 years-plus service life for a two-ply installation with any of these products with good installation and roof maintenance. Technical reps at the three firms confirmed this, but stressed the importance of proper installation and maintenance. For example, plastic cap roofing nails should be used on the underlayment, never staples.
Whatever you use in the field, make sure you use a self-sealing, fully-adhered flashing membrane at any valleys, roof transitions, and around openings such as skylights.
Fontana G40 Layfast SBS TU35/43 Malarky Right Start UDL
Clay vs. Concrete Tile, Synthetic Underlayment?
I have a Mediterranean-style custom home and currently have authentic one-piece clay S-tiles. I had fumigation done because of termites and the roof was extensively damaged. I am not sure should if I should go with concrete tiles or the same clay tiles. Also what kind of double underlayment is recommended? I have been recommended Fontana G40 for underlayment or synthetic Sharkskin. I have been reading about concrete tiles that their color will fade over time, are heavy, and are 30% less expensive than clay tiles. The 30% extra cost is not an is an issue. I just need the right advise because overall it is an expensive project. I would appreciate your response at your earliest.
You are smart to focus on the underlayment as that is the true waterproofing layer on a tile roof. The industry-standard minimum underlayment for a tile roof with a slope of 4:12 or greater is a single layer of ASTM-rated #30 felt paper. Cheaper felt paper without an ASTM rating, widely sold in home centers, is much thinner and should not be used. (The ASTM standards are D226 Type II or D4869 Type IV for organic felt; D6757 or D4601Type II for fiberglass products.)
A double layer of underlayment provides twice the protection and longevity as a single layer and is, therefore, highly recommended. Many tile roofing systems have outlived their felt underlayments, requiring expensive repairs. No sense in putting a 10 year underlayment on a 50-year roof! The specific underlayment used should be suitable for the climate. Freezing weather, extreme heat, and windblown rain require appropriate materials and installation.
Nowadays there are many more options than asphalt felt – primarily rubber-modified asphalt (SBS) products and synthetics, such as the Sharkskin and Titanium lines of products.
Adding synthetic rubber (SBS) to asphalt generally improves its flexibility, its performance in cold and hot weather, and its overall durability and longevity. Modified asphalt has been widely used in self-adhesive flashing membranes such as Grace Ice & Water Shield and is now used in many premium roofing underlayments as well such as Fontana G-40. Similar products include Layfast SBS TU35/43 (MB Technology) and Malarky Right-Start UDL. These are all similar products which use SBS-modified asphalt on a fiberglass base. All meet ASTM standards for 30-pound underlayment and should provide a long service life for a two-ply installation. Warranties are typically for 20 years, but they should last a lot longer.
There are also a number of newer synthetics on the market made from a variety of materials. Some, like Sharkskin, carry very long warranties. But like most roofing warranties, they don’t really cover much. For example, Sharkskin’s 50-year-warranty and Titanium’s lifetime warranty cover only the original cost of the material, not its installation. This might cover 10% of the actual cost of repairs.
Some of the synthetic underlayments provide a Class A fire rating, improved walkability on steep slopes, and easier installation due to their light weight and resistance to tearing. The easy installation makes them popular with many roofing contractors. How well they will last over the long haul is unknown, however, and manufacturing standards have not yet been established.
Personally, I would choose two layers of G40 over Sharkskin as the material has been around longer and has a proven track record. I would also consider an upgrade to heavier SBS-modified product such as Layfast TU43, or possibly TU70 for especially harsh conditions. A double layer of TU43 now carries a 30-year warranty, one of the longest for an SBS-modified underlayment. Whatever you choose, make sure you use a self-adhered flashing membrane at valleys and transitions and around skylights or other openings.
Sounds like you have done your homework about clay vs. concrete tile. As you point out, concrete tiles are less expensive and lighter, but will fade somewhat over time. Also because they are more porous, they can get stained. Clay tiles will keep their color pretty much forever whether natural or with a ceramic finish. If you are in a freezing climate, however, concrete tiles are a better choice as they are less prone to cracking.
Good quality concrete tiles should last 30 to 50 years, while clay tiles may still be going strong in 100 years, well after you and I are long gone. Best of luck with your new roof!
Are Composite Roofing Tiles Durable?
Are composite roofing tiles very popular in California? I love the look of slate tiles and I thought that these were common in California. How durable are they?
As far as I know, traditional clay tiles are still the most common (and most expensive) roofing material on the West Coast, followed by concrete tiles, and then composite tiles.
Good quality concrete tiles should last 30-50 years. Clay tiles may last much longer. Composite tiles vary in their composition and lifespan.
Composite tiles are made from a variety of materials so it is hard to generalize about quality and longevity. They are lighter weight than concrete or clay and less costly. They use various combinations of fiber-cement, plastics, polymers, synthetic rubber, and various fillers.
If you go with composite, I would look for a product and company with a good track record and products that have been in the field, in your climate, for 10 to 20 years. Check the product online for consumer complaints, lawsuits, etc. A lot of composite roofing and decking products have not lived up to expectations and ended up being pulled from the market.
Look for a strong warranty, which shows some level of confidence in the product. But remember that most roofing warranties are for materials only, are prorated by years of use, and require that the product be installed exactly as the manufacturer specified. And the company has to still be around when you make the claim. So, in reality, roofing product warranties are usually not worth very much.
elaina viola says
SBS-modified 40 or 90 lb felt is much higher quality than 30 lb paper. Two layers of unmodified 30 is cheaper than 1 layer of modified 90. I was disappointed to read your answer. I disagree with many specifics you gave, including the lack of the term “modified” and the actual weights vs names. Please refer to Malarkey Building Products for accurate information.
I agree that SBS-modified asphalt underlayment is, in general, a much better product than unmodified asphalt felt, and stated that above. I also agree that underlayments manufactured to ASTM standards are generally better than unrated products, which are often inferior and of inconsistent quality.
Different companies offer different formulations and different weights, so I’m not sure what you find incorrect. Malarky’s 40-pound SBS modified underlayment is certainly a good product. Similar high quality SBS-modified underlayments are made by Fontana (40-pound) and MBTechnology, which offers 37-, 43- and 70-pound SBS-modified underlayment. You can find links to these products here.
Since the nominal weight with any of these products does not always match the actual weight, it’s always a good idea to check the product specifications before purchasing. Also confirm that it meets the appropriate ASTM or UL product standards and pay attention to the installation instructions or risk poor performance and a voided warranty.
Brad -- A Roofer in Findlay says
I thought you answered the question pretty accurately. I too have moved away from the 90 pound paper to go with a different type of material like you mentioned. Thanks. Brad, Findlay Roofers, Findlay, OH