Q: Several roofing contractors have provided quotes to repair or replace our 30-year-old concrete tile roof. Some are saying we should replace the roof and others are recommending repair.
With replacing there are so many material options that it is extremely difficult to determine which way to go.
How can I get advice independent advice on what to do? — Anthony
A: There is no simple answer to your question. The best option depends on many variables, including your budget, climate, and taste in roofing materials. Whether to repair or replace depends on the conditions of the existing tiles, underlayment, and flashing, as well as your climate and how well the roof was maintained..
Concrete tiles can last 50 years or more under ideal conditions. If the tiles are still in very good condition after 20 years, you can expect at least another 20 to 30 years of service.
Flashings and Underlayment
Flashings and underlayment rarely last as long as the roofing tiles. The most common flashing metal is galvanized steel. The gauge of the steel and the thickness of the galvanized coating, along with environmental conditions, determine the material’s longevity. The IRC building code calls for minimum 26-gauge steel with a G90 galvanized coating.
Under good conditions, heavy-gauge galvanized flashings can last 25 years or more, but may start failing in as little as 15 years. Air pollution and salt spray in coastal areas will accelerate corrosion. Also leaving debris on the roof that traps moisture will speed up corrosion. Premium metals will last longer. For the best performance, use copper and stainless-steel which will last indefinitely.
Underlayment choices are probably the most confusing. I would avoid traditional asphalt felt as the quality has diminished over the years. It’s worth spending extra for a premium underlayment.
Synthetic underlayments are very popular with roofing contractors as they are easy to install and provide a walkable surface. There are many choices and lots of marketing claims, but not much real-world performance data and no industry standards to go by. To some extent, you get what you pay for, so the thicker, more expensive materials are usually better. Synthetics tend to be very waterproof, but do not seal well around nail penetrations, which can lead to leakage with tile roofs.
Modified-asphalt underlayments are a good choice. They are similar to asphalt felt, but the rubber additives provide better strength, durability, and longevity. Most seal well around nail penetrations. A double layer of rubber-modified asphalt is a very good choice.
Self-adhesive underlayments are considered the best choice by many roofers. They create an impenetrable waterproof layer that seals completely around any penetrations. One downside is that removal is difficult or impossible when re-roofing, so your choices are to replace the sheathing or leave the old underlayment in place. Go with a well-established brand with a proven track record as not all products work as advertised. Read more on peel-and-stick underlayments.
Concrete, Clay, or Composite Tile
In choosing a tile material, the most common choices are concrete and clay. Clay tile are more expensive and more prone to breakage, but will generally outlast concrete tiles by several decades.
In recent years, a number of metal and composite materials have been introduced that either replace or mimic traditional tiles. In general, both metal and composite materials are lighter than clay or concrete, which may be an issue in homes where the roof structure is not designed for tile. Metal and composite materials are also less prone to breakage. Metal is very durable, but can be noisy during rainstorms.
The durability and lifespan of composites will vary with the specific product. Composites often make use of recycled content and may include various types of synthetic rubber and plastic as well as fiber-cement. Pay carful attention to warranties and look for products with a proven track record. Also, purchase some extra material for future repairs as matching the style and color 10 years from now could be difficult.
Comparing costs, warranties, and appearance can help you decide. Also the advice of an experienced roofing contractor who installs multiple materials can help you sort out the pros and cons of each type.
Repair vs. Replace
As for repair vs. replace, that is largely a financial decision. If the repair work comes with a good warranty, it is certainly a viable option. It’s like an old car: they are worth repairing up to the point where it’s hard to justify putting more money into the old junker. In some cases, replacing the underlayment and flashings while salvaging the tiles with a “lift and relay” job can make sense. But if the tiles are more than 20 or 30 years old, it rarely makes economic sense to reuse them. — Steve Bliss, Editor, BuildingAdvisor.com