IN THIS ARTICLE
Site Problems vs. Assets
Slope
Surface Water
Subsurface Water
Soil Types
Filled Land
Radon
Difficult Sites View all SITE PREP articles
A piece of land that looks gorgeous to the buyer’s eye may look like trouble to an experienced builder. Issues such as soil type, the presence of ledge, high water tables, and poor drainage are just some of the issues that can complicate construction and drive up costs.
Some issues, such as the slope of the site are obvious. If the site drops about six feet over the width of the house, you will need a deeper foundation on the low side (or a stepped-down foundation). Soil types are less obvious, but certain types of problem soils can make a site challenging and expensive to build on.
Water is often the most difficult site issue to understand and predict. Surface water, including runoff from rain and snow, can cause erosion and flooded basements if not properly managed. Subsurface water can interfere with septic systems and flood basements, often in the spring or rainy season when the water table is highest.
Both issues can be dealt with using proper grading and drainage techniques. However, managing subsurface water with curtain drains, extensive subsurface drainage, and – if all else fails – sump pumps may be a good reason to walk away and look elsewhere to build.
TURNING SITE PROBLEMS INTO ASSETS
Most site problems can be overcome by an experienced builder with a big enough budget, and some can be turned into assets with a little creativity. A moderately sloped site allows for a walk-out basement and can be regraded to a terraced yard. A rock outcropping can become a focal point in landscaping. A low, wet spot may have potential as a year-round pond. But it’s best to go into a project with your eyes open.
When you are evaluating a building site, think ahead to how the land will work with your general house design. Where would you like to site the house? What areas should be cleared and what left natural? On a sloped site will you build a walk-out, step the building down the slope, or move a lot a earth around to create a level yard with a terraced slope or retaining wall? Keep an open mind and you can often turn a lower-cost “difficult” site into a special home environment.
SLOPED SITES
A little slope is nice for aesthetics and site drainage (drains around a full foundation can drain to daylight), but a steeply sloped site can substantially raise site development costs.
- Moderate slopes. Gentle grades of less than about 10% (a one foot rise over 10 feet) are the easiest to build on. Between 15% and 20%, you should plan to spend a little more on grading and the foundation, which may need to be be stepped down or have deeper footings on the low side. This is a good slope for walk-out basement. See Building on a Slope.
- Steep slopes. Much above about 20%, you may have to do more extensive earth moving, retaining walls, and soil stabilization to create workable grades and prevent erosion. Cut and fill operations can get costly, especially if you have to truck in additional fill. The cost of fill varies greatly depending on what is nearby and accessible, so don’t make assumptions here — get estimates.
- Erosion during the building process can lead to fines (for polluting streams) and extra costs to regrade eroded areas. Some combination of terracing, retaining walls, and special foundation and drainage techniques may be needed to keep the soil and the building itself from sliding down the hill.
- Hillside foundations. Houses are routinely built on extreme grades of 50% or more in places like California, where hillside home sites are coveted. These buildings all have complex engineered foundations installed by specialists in hillside work, which can be dangerous and is always very expensive. Foundations for these homes cost more than many houses built on flatter sites.
- Drainage of steep slopes. On steep sites, pay special attention to soils and drainage. Wet, dense soils on the uphill side of a foundation can exert excessive force on the uphill foundation wall – like a dam holding back a lake of mud. And fast-running water on a steep slope can lead to excessive erosion if not managed properly. Areas of the country subject to heavy winter rains and mudslides are of special concern. When in doubt, get input from a civil or geotechnical engineer familiar with local conditions.
- Septic Systems. Very steep sites may require specially engineered piping and leach fields. The maximum allowable slope depends on local regulations, but typically ranges from 20% to 30%.
SURFACE WATER
Water can be a wonderful amenity on a building site. Most people enjoy a water view, a swimming pond, or a babbling brook. However, water can also be your biggest enemy on a building site and can make or break a project. Most problems can be solved with enough money, but it may not be worth the expense and not all efforts work as planned. Engineers can figure out a way to build on wettest of sites, but you should understand the costs and risks before proceeding.
Unless you are trained in civil engineering, understanding the effects of water on your site in both dry and wet seasons can be challenging. If possible, view your site in the wettest season – after the snow melts in New England, for example. The cute little brook that runs across the site could turn into a raging river, a low spot on the site might become a pond. On the other hand, a lovely pond in the spring might become a mud-caked pit in the dry season.
If your site has drainage ditches, culverts, or other man-made efforts to manage site drainage, ask when they were installed, for what purpose, and how well they work. Look for evidence of high water in any ditch, stream, or other natural or man-made water course. If possible, visit the site after a heavy rain to see watch the drainage patterns in action. Does your chosen house site sit high and dry or look more like a duck pond? Most issues can be corrected with grading and planned drainage, but a very wet site may require expensive engineering to get right.
It is especially important to understand drainage patterns on a hillside site or one at the bottom of a hill. Runoff from rain and snowmelt can usually be channeled around your building by some combination of grading, swales, and culverts.
Swales. On sites with extensive surface water, for example, at the bottom of a hill, surface water can be directed away from the house by shallow ditches, called “swales”. These are often located between house lots or along roads and often drain toward the front or rear of the lots. They are typically covered with lawn and may be incorporated into the landscaping with water-tolerant plants.
The grass slows the flow of water, promoting infiltration back into the soil and evaporation. The grass and other plantings are also critical to stabilize the soil and prevent erosion along the drainage path.
See also Managing Roof & Yard Runoff
Erosion. Depending on soil type and vegetation, erosion can also be a problem on disturbed areas of the site that conduct water or where water is discharged. Stones, plantings, or landscaping elements that slow down the flow of water will help prevent erosion in these areas.
SUBSURFACE WATER
If surface water is challenging to understand, subsurface “groundwater” can be downright mystifying. The basics of aquifers and water tables is discussed in the section on well drilling. From a building standpoint, you don’t want the lowest floor in your house below the seasonal high water table. This is primarily a problem with full basements.
It’s possible to keep water out a basement built below the water table, but it’s expensive to build a house that’s a tight as a boat and prone to failure. In the end, you may end up with a sump pump running throughout the wet season. Also, excavating and pouring concrete footings in a wet hole is tricky and can lead to poor quality concrete or excessive settling.
It’s not impossible to build a dry house on a wet site. The water table can be lowered around the house site by “dewatering” techniques such as curtain drains (also called “French drains”). This may involve drainage ditches around the property as well as a large bed of gravel or crushed stone below the foundation that drains to daylight or a storm sewer.
In one house I designed, water ran continuously in the springtime through a deep gravel bed under the foundation, but the basement was dry as a bone. The land developer used a sophisticated engineered solution. To trust the average builder to get this right without the input of a civil or geotechnical engineer would be risky.
One way to avoid basement water problems is to build on a concrete slab-on-grade, as is commonly done in some regions. Crawlspace construction is another option as long as the crawlspace is safely above the seasonal high water table and built with an effective vapor barrier on the ground. A chronically wet crawlspace is worse than a wet basement, since mold and rot are often undetected until extensive damage is done.
See also: Building a Dry Basement Basement Leakage Q&As
SOIL TYPES
Soils have a mix of particles from extremely fine clays and fine silts to course sand and gravel. You can get a pretty good idea of the soil type by examining a handful of soil taken from below the topsoil, the dark, organic matter that’s usually no more 6 to 10 inches deep. You cannot see the individual particles in soils high in clay. When squeezed, this soil feels smooth and can be rolled into thin shapes. Granular soils with more silt, sand, and gravel have visible particles that feel more gritty. They will not hold a shape when squeezed.
- Clays. Soils with high clay content tend to hold a lot of water and drain poorly. Soft clays have limited load bearing ability, required foundation modifications. In cold climates, clay soils are prone to frost heaves, which can damage foundations, slabs, and piers that support decks and porches. Expansive clays, common in some parts of the country, expand when wet with enough force to destroy foundations, and shrink when dry causing excessive settlement. Most non-expansive clay soils are OK to build on, but will require more granular fill to be brought in for backfilling, reducing problems with drainage and frost heaves. Expansive clays require expensive engineered foundations.
- Granular soils. These are ideal for building and drainage. They have high load-bearing capacity and drain well. Areas where the soil is pure sand are easy to excavate and build on, but may need some extra help with landscaping and grading to avoid erosion.
- Ledge. Sites with solid or fractured ledge near the surface present problems with excavation, drainage, and septic systems. Blasting is expensive and carries liability in the event that a neighbor claims that your blasting cracked their foundation (blasting contractors routinely photograph and document surrounding properties as a safeguard). Foundations can be formed around and pinned to solid ledge, perhaps leaving a granite outcropping in your basement. Sealing between the foundation and the ledge can also be difficult and prone to leakage. When possible, it is much less costly to leave the ledge in place and work around it. Since blasting is often bid by the cubic yard, and the amount of stone is unknown, the cost can be difficult to estimate.
Read more on Problem Soils
FILLED LAND
Ever seen those signs reading “Clean Fill Wanted.” Well that “clean” fill usually ends up filling in the low spots on someone’s land. If you have the misfortune of buying that land and building on top of the fill, your foundation could settle and crack significantly, causing damage throughout the house.
If the fill was, in fact, clean – that is, free of tree stumps, garbage, topsoil, toxic materials, and organic material – and was properly compacted when it was placed (compacting one shallow layer or “lift” of fill at a time), then it would be fine to build on. However, these are big if’s.
If you have reason to believe that the land you are viewing has been substantially altered, you may need to examine the soil with a core sample or test pit. In general, uncompacted fill needs to be removed and compacted properly, or replaced with properly compacted granular materials, such as sand, gravel, or stone, before building. A similar problem exists if the excavator digs too deep and the foundation is placed on disturbed soil. Unless the replaced soil is properly compacted, the foundation may settle and crack.
Read more on Building on Filled Land
RADON
While you don’t hear much about radon these days, it’s still down there in the soil in some areas of the U.S, and still responsible for a large number of lung cancer deaths, according to health experts. Some regions, such as the Reading Prong area in the mid-Atlantic states, are known “hot spots” and are identified as Zone 1 (highest risk) on the EPA Radon Map.
Zone 2 is considered moderate risk and Zone 3 low risk. The mapping is not very precise, however, and state authorities, whom you can find through the EPA radon website, may have better information about your particular state. You can also find more detailed state-by-state radon risk maps, which identify individual counties.
Radon Testing. While radon maps can provide a rough guide to the average risk in your area, there’s no way to predict radon levels in an individual house without testing the building after construction. Testing of the soil prior to building does not reliably predict household levels. Testing after construction is inexpensive and easy to do yourself.
You can purchase a test kit at any good hardware store or online. Also, many state health departments provide high-quality test kits to homeowners at discount prices. A short-term test of 2 to 3 days can identify a problem, but since levels may vary from day to day, a longer term test is needed for an accurate assessment.
Closely follow the instructions that come with the test kit. The test kits are typically placed in a frequently used room on the lowest level of the home that is used regularly (typically the basement level or first floor). The kit should be placed in a room that is used regularly such as a den or bedroom, but not a kitchen or bathroom.
For a short-term test, keep windows and outside doors closed and do not run ventilation systems or exhaust fans for any length of time. Windows and doors should not be left open for at least 12 hours before the test. You can learn more about radon testing from the EPA’s Citizen’s Guide to Radon.
Radon Removal. In a new home in Zone 1, the EPA recommends that you install a passive radon mitigation system when you build– essentially a PVC pipe run from the gravel bed under the slab or basement floor through the roof, like a plumbing vent (in additional to placing a vapor barrier under the slab and sealing around the slab edges). If radon levels are found to be high, you add an inexpensive inline fan and, voilà, you’ve got a highly effective radon mitigation system.
If you’re building in Zone 2 or 3, but are still concerned, you can inexpensively safeguard your new home by running a short length of PVC pipe through the slab or basement floor into the gravel bed, and then cap the pipe. If the house is later found to have radon, the pipe can be extended through the roof to create a passive or active system.
If properly installed, sub-slab ventilation systems reduce indoor radon levels by 80 t0 99%. With gravel or permeable soil under the slab, the reduction is typically 95% or greater.
Read more on Radon Risks and Mitigation
DIFFICULT SITES
Other than sites that are illegal to build on, there are few sites that are truly unbuildable. Just take a look at the hill towns in Europe, still standing after hundreds of years of clinging to precipitous hillsides – and built without the benefit of steel, reinforced concrete, and construction cranes.
In many areas of the country, the best building sites are take or prohibitively expensive, so if you have a tight budget, you are probably going to see a lot of less than optimal sites. They may be steep, rocky, or wet, hard to access, or require alternative septic systems or special engineered foundations. The costs of developing a site can vary enormously depending on its specific characteristics and your construction plans, so any site you are seriously considering needs to be individually assessed.
If you can buy the land at the right price, a “difficult” site may be a good deal. With a little creativity, you can often turn a difficult site into something unique and appealing. Handled properly, water, rocks, and steep slopes can become important landscaping features that make your building site special.
The key is to understand the costs and risks ahead of time. Hiring a civil or geotechnical engineer for a couple of hours can be money well spent. If necessary bring in a foundation contractor, blasting contractor, or septic system installer familiar with local conditions to give their opinion and maybe a ballpark estimate. If a septic system plan is already completed, get an estimate from a contractor.
Use the Typical Site Development Costs checklist as a starting point to work up a realistic estimate of site development costs. Then use the first five sections of the Estimating Worksheet (General Requirements, Site Prep, On-Site Water/Sewerage, Utilities, and Excavation/Earthwork) to work up a detailed estimate, which you can use to make your bid. Or, if it’s too expensive or will never be right for you, walk away. Don’t fall in love with a piece of land and proceed based on wishful thinking. Too many projects get abandoned when the owners discover that the real costs of going forward are so much higher than they imagined.
See also Foundations & Sitework Sitework Q&As
David Lynch says
How Much Ledge Needs Removal for Pipe Trench?
We are converting our home from a Septic System to Town sewage; the septic is starting to fail The Ex Contractor/Drain Layer gave me a price f or his portion of job but stated any ledge would cost $ 1200 day plus $250 hour. The house is 53 years old and sits on a hill with a pretty steep grade about 300 linear feet from the road where the town sewer lies. Before starting to dig, is there any way to determine if there is any ledge and if so how much. I bought this house in 1978 to keep my family close to family because I was in the military working out of Ft Bragg and constantly being sent out of country on missions . Retired after Dessert Storm and thought I was “home free”. This could impact our savings unless I can determine before hand a way to find out if , how much and where any ledge might exist Tewksbury Ma location. Can’t even sell unless hook up to town is done Please advise. Thank you
buildingadvisor says
It’s never easy to determine the costs of excavation when there are large amounts of buried ledge.
In your case, I would start by determining the required depth and course of the drainage pipe, and then dig a number of small test pits along the route to sample the subsurface conditions. If there is a small amount of ledge in few spots, then the cost of removal will be modest and can often be done with rock hammers and other mechanical equipment rather than blasting. If a great deal of ledge is encountered, you may want to do further investigation by drilling some core samples.
With this information, an excavation contractor should be able to give you a reasonably accurate estimate of the cost involved. Ask for a cost per cu. yd. of stone removed, and ask for a not-to-exceed price. Any type of unit pricing is better than an open ended hourly/daily rate.
You may also wish to explore alternative routes to reach the city hookup that encounter less ledge. A longer run may be cheaper if there is less rock to remove.
Ledge can be mapped to some extent with high-tech equipment such as ground-penetrating radar and electromagnetic systems. However, these would probably cost more than digging test holes. In some cases, you can find people at a local college or technical school who are willing to use your site as learning experience. Contact the engineering departments — focusing on soil, civil, and geotechnical engineering — to see if they would like to map out the ledge on your site.
Gerri M says
Three Surveys Show Different Slopes & Boundaries
We own a hillside lot with an existing old home. In working towards a remodel and addition we’ve had the lot surveyed three times (for a couple reasons: loss of data, death of surveyor and loss of data again and a final one… This final survey was made with 1′ interval rather two feet as the previous ones and concluded with 10 percent higher total contour length resulting in essentially 4 percent higher slope (besides reporting out that one of property lines shown earlier was 6′ in error against us).
In looking at all three surveys it appears that there is wide latitude in a surveyors’ discretion of what constitutes a proper contour line (noisy fly-walk like around gardening artifacts versus tracking primary gradient contour). I’ve not found much in the proper professional approach to avoiding penalizing an owner for gardening artifacts, such as 6″ timber garden beds, that contribute to what seems an artificially high average slope.
Any guidance in this realm? Many thanks!
buildingadvisor says
Sounds like your survey process has not gone smoothly and left you with more questions than answers. That is unfortunate, as the whole point of a survey is to provide an accurate record of your land’s boundaries. More extensive surveys will identify contours, easements, well and septic systems, and other as-built elements.
There are several different types of surveys — from simply finding your lot corners to a full-scale ALTA survey. From your description, it sounds like you obtained a “boundary” survey, which accurately marks your property lines to conform with public records. You can include existing buildings and other improvements as well as easements if desired. This type of survey does not usually include topographic information, but it sounds like you added that to the survey.
Keep in mind that all measurements are based on a theoretical flat surface projected onto the slope of the land. Regardless of the contours, the lot lines and corners remain in the same place. The slope of the site will effect the design of the addition, but modest slopes are easy to handle with a stepped foundation.
That said, you would not be “penalized” or rewarded for building garden beds or otherwise changing the contours. Your lot corners and lot lines stay put. However, relocating the property line by 6 feet could be problematic if it creates a setback violation for your existing home or planned expansion.
In most cases, your current home and/or septic system will be grandfathered under zoning laws in place when the house was built. But adding to a “non-conforming” building (that is, one that does not conform to zoning laws) may require a variance or special permit. Best to sort this out before getting too far along with your construction plans.
Read more on Surveys
Jessica says
Can You Build On Recharge Basin?
Can you build a house on land that is categorized as “recharge basins & drainage conduits”?
buildingadvisor says
A recharge basin is a natural or manmade pond that collects water from rain or snowmelt and allows it to percolate into the soil to recharge the aquifer. Not exactly sure what you mean by a “drainage conduit,” but I assume it is a channel such as a swale, which is a shallow ditch used to manage site drainage. There may be pipes, gravel beds, or other devices to channel and direct the water – perhaps into the recharge basin.
So, no, you wouldn’t want to build in the middle of a pond or drainage channel.
It’s possible that you can build elsewhere on the site or that these elements can be relocated for the purpose of siting the house. In that case, you would need to be extra careful in building the foundation – to ensure that it is built on undisturbed soil or engineered fill. Building on filled land or other problem soils can lead to serious structural problems
Moe says
Contract Clause for Soils and Foundations?
Are you aware of any standard contact clauses in the Scope of Work related to soils and foundations in residential contracts? I am looking for contract language dealing with soil testing for moisture content, bearing capacity, etc,, as well as foundation details. I am especially interested in home renovations and new home construction.
buildingadvisor says
The basic model contract that we provide does not specifically address soils or foundations.
In residential contracts, the foundation details may be called out in the plans and/or written into the specifications. The Scope of Work in our model contract states that the work shall be done “in accordance with all applicable Building Codes and also in accordance with all the Contract Documents specified in this Agreement. All products and materials shall be installed according to manufacturer’s written instructions and construction industry standards.”
The International Residential Code (IRC) goes into a lot of detail about footing sizes for various loads and soil conditions. You can view the IRC section on foundations.
It is generally the responsibility of the owner, designer, or engineer to provide the contractor with the foundation and drainage plan. If soil testing is required, then he owner or architect would hire a qualified consultant. If you want the contractor to take on that responsibility, then you would need to add special language to the contract, as you suggest.
You would also need to find a contractor with the expertise and willingness to take on this responsibility. If there are problem soils, such as expansive clay, a filled site, a high water table, or other site conditions requiring something other than a standard foundation, then you really need to address these at the design stage – or you may live to regret it.
You can find some articles on problem soils at this link.
Best of luck!
jani says
Can I Fill Land That Floods In Rainy Season?
Good day,
I bought a piece of land in a flood-prone subdivision previously, then I have asked the engineer of the subdivision who is the current administrator if it’s okay to top-up the lot with gravel and dirt since it has became a mini lake due to the rainy season. But the main reason is to make it higher and take the rainy opportunity to compact the land for future house construction.
That engineer said that it’s up to the builder company which I’ll be hiring to do the topping up.
Do you think this is a sound advise? Isn’t it better to top up now and let the land sit and settle for compaction?
Thank you.
buildingadvisor says
Were you aware that the land you bought was in a flood-prone area? Do you know if it is in a FEMA-designated flood zone? That may mean mandatory federal flood insurance, more difficulty with construction loans, and special building requirements. This might include elevating your home, keeping all living space and mechanical/electrical systems above anticipated flood levels, and other special construction details.
If the developer failed to disclose this information, they may have violated your state’s real estate disclosure laws, and may be liable for some of the added cost you will incur in building. Regardless, it sounds like the developer did poor job with site drainage if your building site turns into a pond every spring.
As for building on fill, this is always risky. Letting it sit for a few years is not a reliable form of compaction. Some soils will self-compact given enough time and water, but I wouldn’t count on this to support my new home. Foundations placed on filled land risk serious structural problems that are difficult and very costly to repair.
All foundations should go on suitable “undisturbed” soil or engineered fill that has been properly compacted. This is usually granular soil (sand and gravel) that is placed in shallow layers, called “lifts” that are each compacted with machinery before the next lift is added.
If the existed soil has not already been disturbed, you may be able to place your foundation a couple of feet down (onto solid ground below the topsoil) and build your foundation wall high enough to provide the necessary elevation. The house will be resting on undisturbed ground. However, the fill around the house should still be compacted or you may find your yard, driveway, front steps, etc., sinking over the next several years as the fill naturally settles. How rapidly this occurs depends on the soil type, moisture content, rainfall, and drainage patterns, so it is difficult to predict.
It is not surprising that the engineer who works for the developer does interested in giving you professional advice on building. After all, he is working for the developer, now you, and does not want to be responsible if your building has problems down the line. If you want independent recommendations for a keeping your foundation from cracking and keeping your house above water, you will need to hire your own engineer (geotechnical or civil) to evaluate the site and make recommendations for safe building. It is certainly possible to build on a wet or filled site – look at Venice or most of south Florida – but it is also more costly and requires special expertise.
You could rely on a contractor to handle this aspect of the job, but they may and may not have the necessary expertise. For my money, I would buy a few hours of a good engineer’s time to gain some piece of mind. You only get one chance to do this work correctly.
Read more on Building on Filled Land.
Best of luck with your new home. Hope it all works out for you!
Laney says
Good morning Steve,
I really appreciate your feedback and very helpful advise on this matter. I am now planning to negotiate with a gravel supplier how many dump trucks of dirt will be needed to top up the land and make it level up with the main road.
I was aware of floods nearby when there’s a heavy downpour but because I loved the area and price of the property, I went for it. I also understand that a poor foundation will lead to many issues and headaches down the road. I’ve seen one property, a 2-story townhouse built on land that used to be a rubbish dump site, tilt on one side because one side’s foundation started to sink. I hope I don’t get that issue in the future.
Thank you once again and have a good day.
Nick says
Hi Jani, how did the build go? What did you end up doing to prepare the soil for development?
Best,
Nick
Celine Dalfonso says
What Type of Engineer For Wet Building Site?
I have a three-acre property with primarily clay base soil. There is also a man-made pond on the property. The property is very wet with many low-lying areas and I suspect the pond is a contributor. When looking to bring in a professional, it was suggested I hire an engineer for a consultation. Can you tell me what kind of engineer is best for this type of problem?
buildingadvisor says
My first choice would be a geotechnical or soils engineer (two names for the same thing). These professions focus on designing foundations and site work, including dealing with the surrounding soils, and surface and subsurface drainage.
Geotechnical and structural engineering are considered subspecialties of civil engineering. Civil engineers design and oversee the construction of roads, bridges, dams, water and sewage systems, and other infrastructure projects. Most civil engineers could also solve your problem.
The more important thing is to find an engineer who has experience with residential-scale projects. This is often an independent practitioner or small firm. Large engineering firms are may have limited experience with small jobs like yours, so the solutions they suggest may have the complexity – and cost – more suitable to a hydroelectric dam than to a soggy home building site.
Make sure you ask whether they have worked on projects similar to yours and get an estimate (preferably a fixed bid) for their work before proceeding. A good engineer can suggest practical and economical solutions and can often help you find a competent contractor who is a good fit for the job.
Read more on Surface Drainage Subsurface Drainage
Ken Dunbar says
Concerns When Building Near Lake
What should I look out for building near a lake? The lot is about 4ft higher than the spillway and would likely need to be 2ft higher to be safe from ever flooding. Is filling 2ft realistic for a $250k for a 2200 sq ft build?
buildingadvisor says
Thanks for your interest in BuildingAdvisor.com.
Waterfront homes are wonderful – wish I had one. But building on a wet site can mean a lifetime of building problems if the water is not properly managed.
The water table interacts with the lakes level, but is not necessarily in the same plane. You’d be wise to dig a test pit to find where the seasonal high water level is based on markings (mottling) in the soil. A soil scientist or engineer usually does this inspection as part of the perc test. Also talk to neighbors with homes around the lake – what problems have they experienced over the years with wet basements, insects, or other problems you may not have thought of like noisy jet skis, algae blooms, or whatever.
For obvious reasons, you don’t want the bottom floor or basement floor level to be below the water table any part of the year. A slab-on-grade foundation is often your best option. A crawlspace can also work it is safely above the water table and the soil is well sealed. Wet excavation holes for footings can also be problematic, but manageable by an experienced contractor.
Not sure how much area you need to raise two feet, or the cost of fill in your area, so it’s hard to comment on the cost. However, you don’t need to raise the whole lot, just directly around the house with a slope downward to the original grade. Good landscaping using terracing and retaining walls, if needed, could soften the visual impact.
Also remember that the typical foundation sticks up a minimum of 8 inches above grade, but 12 to 18 inches is better, especially on flat sites where you need to add extra backfill to create the recommended slope away from the foundation. Some of this can be leftover soil from the excavation, and the rest can be purchased fill and topsoil.
Other issues to consider:
• Foundation. If you decide on a full foundation, make sure the slab is safely above the water table, and consider a full waterproofing system, not just dampproofing.
• Septic system. Close to surface water, some jurisdiction have very stringent rules for septic systems that can double the price of your system.
Regarding the budget, it sounds overly optimistic to me. Assuming this is just for the building and none of the site development, including well and septic, that comes to $114 per sq. ft. Where I live in the Northeast new custom construction typically costs from $150 to $200 per sq. ft. In lower-cost areas, you may see costs as low as $125 per sq. ft. for a house of this size. Square-foot pricing of houses can be useful for a ballpark estimate, but can also be very misleading. Projects almost always end up costing more than anticipated, so make sure a contingency fund is part of your budget. Understanding why so many projects come in over budget can help you minimized “budget creep.”
Best of luck with your new home. When you’re drinking a beer on the deck of your new home overlooking the pond, all of this hassle will just fade away!
Matts says
How Much Flat Land Is Needed to Build?
How much of a 35,000-plus square foot lot should be flat and usable for building a home? The property is in Altadena, California.
buildingadvisor says
It’s possible to build on a site with no flat land. On a moderate slope, you can often build down the slope with a stepped foundation and two levels or a walk-out basement. You can grade to create level yard areas in the front and back of the house, with sloping or stepped side yards. About 7 feet of drop from the front of the house to the back in ideal for a walk-out.
If you have a specific house design and yard area in mind, you can establish the flat area need for the house footprint and yard. With a moderate slope, you can probably achieve this by “cut and fill” grading or bringing in new fill to create a level area. Depending on the slope, retaining walls may be needed at the front and/or back of the flat area.
If you don’t mind living on a sloping site, you don’t need any flat area as you can use a stepped foundation to build along the slope. Beyond a moderate slope, however, building costs increase rapidly. As I’m sure you are aware, some people build on very steep lots in California using sophisticated (and expensive) engineered foundations and retaining walls to stabilize the soil and building, comply with seismic codes, and provide some usable yard and garden space. The terraced gardens of Machu Picchu have lasted over 1,000 years — with no rebar!
I’d suggest having a contractor or engineer take a look at the site to give you an idea of the cost and complexity of the type and size of residence you have in mind.
Read more about Evaluating Steep Sites Building on Sloped Sites
Naresh says
Can Neighbor Place Excavated Dirt On Our Yard?
I have a general question on the backyard of new construction taking place next door. We have steep uphill on our backyard.
We will have 20-foot flat backyard and a sudden uphill that starts right after that. What is the code requirements for the builder to keep the dirt off our backyard? Is there any such code that exists?
Please help.
buildingadvisor says
In general, a contractor working on a neighbor’s land has no right to disturb your property without your express permission. An exception would be when the neighbor holds an easement that allows him specific rights to cross, run utilities, or otherwise make use of a portion of your land.
These principles are not part of the building code, but basic property rights established in common law. As a practical matter, the first step is to contact the land owner to express your concerns and try to work out a mutually agreeable solution. For example, the owner or contractor may not even know where the boundary is located.
If the work truly requires access to your land, get a commitment in writing that they will restore your property to its original condition when the work is done. It’s always best, and cheapest, if you can work these things out through negotiation.
If the other party refuses to work cooperatively, then you may need to hire a lawyer to assert your rights and put them on notice that they will be liable for any costs you incur.
Laurie Engelstad says
Sink Holes Appearing Around House
I think I have a little cavern under my 2 story home built on a hillside. The house is nearly 50 years old and has been rock solid until this year. Now the lower driveway has what appears to be a small sink hole and the pavement around it is also sinking inward to the hole. The downstairs floor is raised some, enough that it is noticeable when walking across it. At the higher end of the house there is another hole I thought might be a gopher hole.
The most important fact…in the middle of the house on the upper level, a crack in the ceiling has appeared (about 1/8″ wide. It runs the depth of the house from front to back (dining room, hallway and 1 bedroom) and down the 2 outside walls approximately 4-6 inches. No cracks show on the outside of the house yet.
My question is: is there a particular type of business that would have a camera with a light that can be put down one of these holes and see what is going on?
buildingadvisor says
There are many possible explanations for your problems, but I don’t think gophers is one of them.
The combination of two sink holes, the floor being raised, and a crack appearing across the entire house, suggests that something is destabilizing your house foundation or structure. If the house has been fine for 50 years, and these problems started recently and rapidly, I would want to address this as soon as possible.
Given the sink hole issue, it sounds like some there may be subsurface erosion or subsidence destabilizing the soils that support your house.
I would suggest have a local engineer take a look – someone with experience working with residential structures. Either a civil, geotechnical, or structural engineer familiar with local conditions would be a good place to start. Some may have video equipment that can peer into your sink hole. Such cameras are often used to inspect chimneys or plumbing systems and could be used for this application as well.
In the meantime, it is important to measure and monitor the problems to see if they are increasing in size. Take lot of pictures and measurements. If you are noticing changes taking place over a short period of time, that indicates that the situation is unstable and needs immediate attention. A sink hole can be dangerous to your home and its inhabitants.
Also contract your insurance agent to see what sort of coverage you have for this type of damage as foundation stabilization can be an expensive proposition.
Read more at these links: Erosion Under Foundation Buried Debris Building On Poor Soils Expansive Clay
Dom says
Building on a Very Steep Site
I am considering building on a sloped .7 acre site. There are two slopes I would be dealing with. There is a 30-40% grade both from left to right as well as from front to back. Wetlands are present at the back of the lot. I’m of course worried about drainage and flooding in my future finished basement, however my builder doesn’t seem to be that concerned. He is planning to regrade the entire lot such that my garage and main level are slightly above the level of the street (instead of about 4 feet below it as the site is now). He said he would also create swales around the lot for drainage. He says he would prefer to avoid a sump if he can avoid it and would much rather use gravity drainage. Everything he says sounds reasonable and I’m sure he’s done this many times before, but I’m still apprehensive. What do you think?
buildingadvisor says
I can’t give a definitive answer as every site is unique and yours certainly presents a lot of challenges. A 30% to 40% grade is extremely steep and requires moving a lot of earth to make it buildable. You will also probably need retaining walls somewhere on the site since leveling one area usually results in a steeper drop somewhere else. Also you will need to stabilize any steep areas to prevent erosion until you can get lawns and plantings established.
Regarding the drainage issues, you need to deal with both surface water and subsurface water. This starts with an understanding of the drainage patterns on the site. Where is the water coming from and where is it going (toward the wetlands)? Swales can safely direct surface water around the structure, but subsurface water will require a system of granular backfill and footing drains to keep water out of your basement.
It sounds like you are planning on a full foundation that you hope to finish some day. You would certainly want the basement floor to be well above the seasonal high water table, which is likely to be near the level of the wetland area.
If you want the below-ground space to be free of moisture problems now and in the future, you will need to do an exceptional job with below grade drainage, waterproofing, and insulation. Since you plan to finish the space, I would recommend full basement waterproofing, not the more common dampproofing, which involves slapping a thin layer of tar on the foundation wall.
Also, adequate insulation of the basement walls and floor, located properly with a layer of gravel below the floor are essential for a warm and dry space suitable for prime living areas.
If you trust your builder to get this all right, then you might be okay. Ask to see some other work he has done on similar building sites. If you’re not sure, it wouldn’t hurt to have a consulting engineer (civil or soils) take a look at the site and the builder’s foundation/drainage plan and make recommendations. This might cost a few hundred dollars – or more in high-cost areas — but can provide you with some peace of mind. Look for an engineer with experience in residential construction or you might find that his recommendations are better suited to a larger project with a larger budget. Engineers do tend to overbuild as a large safety factor is a part of their training. But I have always found their input valuable.
Best of luck with your project!
mary says
Should We Do Survey and Soil Test Before Closing?
My husband and I just purchased a vacant lot (.65 acres) in Colorado. It is in a subdivision that is 90% developed with custom homes that have been built over 20 + years. We have not selected a builder yet (still interviewing) but have been advised by our realtor to begin ordering survey, Geotech & Soil Investigations in case anything turns up before our due-diligence period expires in our purchase contract. Our realtor is not very familiar with land purchases and we don’t know what type of Geotechnical Investigation we should order other than a soil report. I have asked one builder we are interviewing and they said they do all of that but we haven’t hired them yet and I would like to do this independently. Any advice?
buildingadvisor says
If you are planning to use on-site sewage (a septic system), then a perc test is a must before closing on the lot.
Conducting a survey is usually not required if the subdivision has been platted, as the boundaries are usually well established and marked with reasonable accuracy. However reviewing the plat map is a good idea as this will show the boundaries and any easements, rights-of-way, and improvements such as utilities, roads or sidewalks. It will show if the lot corners are marked. If any easements or other encroachments are shown, they should be further investigated in the deed documents.
If the land is not platted, or there are questions about the boundaries, then a survey may be required at some point prior to
A soils investigation is a good idea where there are questions about the feasibility or cost of construction. This might be an unusually steep or wet site, the need for blasting of ledge, or problem soils such as filled land or expansive clay.
Expansive clay is a big problem in many parts of Colorado. While it is possible to build a home on this type of soil it is very costly and requires special expertise. If not done right, a home can be destroyed by excessive movement of the soil. You can read more on Eat this link:
http://coloradogeologicalsurvey.org/geologic-hazards/swelling-soils/
The fact that most of the surrounding lots have 20-year-old homes is a good sign. Still, you are smart to invest a little money up front to avoid large surprises down the road.
Read more at these links: Building on Expansive Clay, Building on Fill, Building on Poor Soils.
Also see: Colorado Geological Survey Report on Swelling Soils
Jane says
Can I Build on Lot With Detention Basin?
We have a great site and are in love with the area, but the lot, which is 2.6 acres has a detention basin in the back left corner. Is there anything we can do to salvage the lot?
buildingadvisor says
Detention basins are shallow manmade ponds designed to temporarily store runoff during heavy storms. This reduces the flow of stormwater into streams and storm sewers to help prevent overloading and localized flooding.
The detention basin is probably part of an engineered drainage plan for the development or subdivision where your lot is located. If so, there is probably a drainage easement that permits the detention basin in that location. You can probably find this out by requesting the deed and subdivision plat at the town building department or county registry of deeds. A surveyor or title search company could also help you determine the status of the easement.
As long as there is sufficient area to build, it’s unlikely that the detention basin would prevent your use of the lot. You might be able to block it visually with plantings, and may need to fence it off for liability reasons, but otherwise it should not be a problem as long as you do not place any permanent structures that interfere with the use of the easement. The specific restrictions will be detailed in the language of the easement.
Steve Bahrani says
Is It Safe To Build on Filled Land?
It used to be against code build a home on a backfilled pond lake or wetland for 30 years. Is that still true?
buildingadvisor says
Building on filled land is always risky as you don’t know when or how the land was filled or what was used. Without digging some test pits, you won’t know the depth of the fill, what type of soil was used, and whether it was “clean” or contained stumps and other debris. In any case, it’s safe to assume that the fill was not properly compacted.
How long it takes for fill to completely settle varies with soil type and site conditions, so I would not base my decision on an arbitrary number. Your local code may specify a minimum number of years, but I would not rely on a rule-of-thumb if I were building a house. For a barn, outbuilding, or deck, you will probably be fine, but for a new home the risks of structural problems are too great.
If this was a former pond or wetland, you will probably have a high water table as well unless the site drainage was altered at some point. This would pose a problem for septic system and construction of a full basement.
If you are determined to build on this site, the best approach is to excavate deeply enough to place your footings on solid, undisturbed soil. Engineered solutions using driven piles or grade beams are also sometimes used on poor quality soils.
If it were me, I would pay a soil or geotechnical engineer evaluate the soil before building. Excessive settlement of a foundation can wreak havoc with cracked concrete, sticking doors and windows, and other structural and finish problems.
Related links: Building on Fill Buried Debris Building on Wet Sites
Susie says
Should You Build in Bowl?
We recently came into the possession of a plot of land about .82 of an acre. It has a “bowl”. The sides of the lot gradually lower to the middle on all four sides. Is it possible to build a house here or are we going to be looking at a lot of grading?
buildingadvisor says
Building in a bowl is not ideal, but since you already own the property, you might as well see what you can make of it. In general, bowls collect water and snowmelt, so they can be pretty soggy in wet seasons. On the other hand, if you have a granula soils that can readily absorb water – or you are in an arid area that doesn’t get a lot of rain, then this may not be a concern.
Also being the lowest spot around, the bowl may be closer to the water table, and could possibly even form a pond during the seasonal high water table. All these things you can determine with a little excavation and observation of the soil profiles by an engineer (civil, soils, or geotechnical).
Assuming the lot is a collection point for runoff from the surrounding properties, you will need to effectively manage the surface water if you wish to develop the site. If the land rises on all sides of the site, you may not be able to grade yourself out of the problem. Instead, you may be able to install a subsurface drainage system using some combination of surface grates, catch basins, curtain drains, and underground drainage pipe to conduct the water to somewhere where it won’t cause problems for you or your neighbors. Some communities let you tie into storm sewers under certain conditions.
Subsurface drainage may work in conjunction with siting the house near the highest point on the land and bringing in some fill as needed around the house. The house could, perhaps have a walk-out in back and the “bowl” refashioned into a lowered back yard.
I have seen downslope lots and even bowl-shaped lots developed successfully, but it takes a little creativity and extra expense. However, it may be less expensive than you think to develop the lot. You may want to contact an architect or landscape architect to do a feasibility study and conceptual design to show you possible solutions that would work on the site.
Best of luck with your project!
karen says
Site Suitable for Walk-Out?
We are looking at a site described as “gently rolling”. Should we have a contractor take a to look to see whether it is suitable for a walk-out basement?
buildingadvisor says
For a standard 8 ft. foundation wall, the lot needs to slope downward about 7 ft. from the front to the walk-out entrance in back. A little less slope of about 4-6 feet works well as the grades can be adjusted in the finished grading around the walk-out. A 7 foot drop over 35 feet is a 20% grade. For steeper sites, you can expect to spend extra money on the foundation and earthwork, as well as retaining walls and landscaping, to stabilize the slope and create usable yard space. See also Building on a Sloped Site.
Talia says
Finding Seasonal High Water Table?
I am looking at purchasing 2 acres, what test do I need to do to make sure that I can have a full underground basement and a pool?
buildingadvisor says
Part of the perc test procedure is the “deep hole” or “observation hole” test. This is simply a rectangular hole dug with a backhoe to about 7 feet deep, used to visually examine the soil types and determine the seasonal high water table. The seasonal high water table is identified by distinctive splotches of color or “mottling” in the soil.
This same type of test pit dug in the area where you plan to put the house, will give you a good idea about the feasibility of building a full basement and a pool.
Your main concerns would be a high water table or ledge. A seasonal water table above the level of your basement floor means that you will be running a sump pump around the clock during the wettest times of the year.
The presence of significant ledge, means that you will have to blast to build a full basement, and may still have challenges keeping water out of the basement. So a slab-on-grade or crawl space might be better bet if you have either of these issues. Best of luck with your building project!
Scott B says
Cracks Developing in House on Filled Land
Four years ago we bought a beautiful new house in a great subdivision. We knew the house was built on a huge amount of fill, but assumed that since it passed inspections, etc., that they’d done everything correctly. Last week I found a very long crack on the outside bricks – 10 to 12 ft. long on one side of the back basement wall. Everything on the inside is finished so I can’t easily see if this crack is in the poured foundation, too, but suspect it is. On the other side of the basement I’ve just noticed that the floor is apparently moving at the block line – the “expansion joint” cut into the floor is getting wider recently. Just found out today that the city required a geo survey of the site after the foundation had been poured. That company signed off on the construction, but I haven’t seen the report. Any suggestions on how to proceed? Waiting on a local structural engineer to call back about this. Should I involve my insurance company? And when? Thank you.
buildingadvisor says
I’m very sorry to hear about your situation. Building on filled land is risky. It takes good on-site quality control for engineered fill to be done correctly. In the absence of careful inspection of materials, proper compaction, and on-site testing, there is a lot that can go wrong – and problems may not show up for several years.
Assuming that settlement of the fill is the cause of your problems – and that is certainly the most likely culprit – then determining who is responsible becomes a legal challenge that, hopefully, your insurance company will take on. Often more than one party ends up splitting the costs based on partial liability as determined by a court or legal negotiations in the face of a lawsuit by the insurance company.
If I were you, I would do exactly what you are doing – finding a good local engineer to take a look before contacting any third parties. That way, you have an independent professional opinion from someone not on any else’s payroll. A structural engineer would be a good place to start, but he may refer you to a geotechnical or soils engineer. I would ask the engineer for a written report describing the damage, cause, and recommended remedial work. The engineer may also recommend contractors who he knows have the required expertise. I would also ask for a ballpark guestimate of costs to see if they will throw out a number.
Hopefully, you can get a written opinion without doing expensive testing involving test pits or core samples. Once you have reasonable confidence that excessive settling of fill is the cause, you will want to contact the insurance company. Repair costs are likely to exceed $10k and could go a lot higher.
I would probably contact my lawyer before calling the insurance company, since this is likely to be a complex process. Assuming the insurance company agrees to fix the problem, you will want to make sure it is fixed in the best possible manner. The insurance company may hire its own experts to determine the cause and type of repair. Depending on the size of the claim, they may go after other parties for compensation (the developer, the engineer that signed off, the earthwork contractor, etc.).
Your lawyer can advise you about how best to approach the insurance company and how to make sure the repairs are done correctly. I would use the lawyer in a limited advisory role to clarify what your legal rights are and how best to proceed. You definitely want an advocate in the insurance claim process, which varies by state law and your specific insurance contract.
Most likely you have the right to use your own engineer to supervise the work and to select your own contractor. You may also have the right be paid directly rather than have the contractor paid by the insurance company. If you control the funds, you will have more control over the outcome. Although you need to be sure the insurance payout will cover the full costs of repair.
In most cases, the insurance company uses its own “private” claims adjuster to determine the value of a loss, and in some cases the insurance adjuster will try to steer the work toward a company that he has a cushy relationship with. In most states, you have the right to hire your own “public” adjuster, who works on your behalf to appraise the work. Ask your lawyer about the public adjuster option. Since there are a number of approaches to stabilizing a sinking foundation, having an engineer and appraiser representing your interests would be advisable.
Best of luck. You can read more on the topic at these links:
https://buildingadvisor.com/building-on-filled-land/
https://inspectapedia.com/structure/Foundation_Damage_Site.php
surani says
Can Drainage Easement Affect Structure?
Hi. We are looking to buy a land with a drainage easement runs underground the length of the land. We understand that we cannot build anything on that designated area other than grass and flower plants. But can it affect the building at all? I mean to the structure, foundation, etc.?
Thanx in advance
buildingadvisor says
Drainage easements are very common in residential subdivisions. Above-grade easements are usually for shallow ditches called “swales” and underground easements are generally for piping to connect to a storm sewer.
For above-ground easements, it’s a good idea to take a look after a heavy rain, or after the snow melts, to see the level of water flow. However, it is usually not a problem and, if fact, is a good thing that the developers have provided for controlled surface drainage.
Underground piping is even less of a problem, especially if the piping is already in place before you build. Otherwise you may have excavation on your property, disturbing whatever lawn or plantings are in place. While the holder of the easement is legally required to restore everything to the condition in which they found it, it may require a couple of phone calls to enforce this provision and it their landscaping work not be quite up to your standards.
You are correct that no permanent structures can be built over the easement, but you may be allowed to locate paving, decks, storage sheds, and similar non-permanent uses in the easement area. Check the specific language of the easement. However, if the easement owner needed to excavate, you would be responsible for the cost of removing and replacing your improvements.
You can read more site drainage and basement leakage at this link.
Dan says
Could An Artesian Well Cause Problems When Building?
Land I am looking at to build on has an Artesian water table running underground through the property. After a very heavy rain, water appears at the ground surface and stays for a week or more. Also water percolates and bubbles for days.
What are the requirements to properly build on this property without water problems?
buildingadvisor says
I have never had the pleasure of building on or near an artesian well. They are not common in my part of the world.
However, I would certainly be cautious about building directly on a spring or artesian well. The water is under natural pressure, bringing it to the surface. Some “flowing” artesian wells have enough pressure to flow naturally indefinitely. Some, like this one, will flow only occasionally under wet conditions.
A flowing artesian well can sometimes be developed into a water feature on the property — like a pond or waterfall — but can also be a nuisance, causing unwanted wet areas or erosion. It can also deplete the aquifer feeding a drilled well on the same property. Using an artesian well for your water supply is a possibility, but these are more vulnerable to surface pollutants than a deep well.
While it is possible to plug an artesian will, there is no guarantee that it will not emerge elsewhere on the property. An experienced well driller should be able to help you evaluate the artesian well and how best to handle it. Underground water is a complex subject and it’s not always 100% clear how it will behave.
To be on the safe side, I would locate the house a safe distance from the well. If it becomes a nuisance, then you can consider plugging it — a job I would leave to well-drilling professionals.
Peter Munanka says
Preventing Erosion on Steep Sites
Hello. I have a plot of land that is extremely steep and the erosion process is ongoing. We want to build soon but we are looking for an erosion control method that will save costs. We are facing a very large loss by the time the land is ready for construction if we use normal methods to control erosion. Any advice would be appreciated.
buildingadvisor says
Stabilizing steep building slopes and preventing erosion are complicated problems that require site-specific solutions taking into account the slope, soil types, vegetation, and drainage patterns. Most approaches use some combination of terracing, retaining walls, lawns and other vegetation, and redirecting site drainage. Extremely steep sites often require engineered solutions and sometime use proprietary products such as Geogrid.
Once the erosion process begins, it can accelerate quickly as the underlying soils are exposed and drainage channels can rapidly grow into deep gullies which speed up water flow and further erosion. In most cases, there is no single quick fix. It sounds like you need to get an engineer in there quickly to assess the situation and recommend effective solutions.
It’s best to work with local people who are familiar with conditions in your area. I would look for a civil, soils, or geotechnical engineer with experience stabilizing steep residential building sites. Many engineers have limited experience with residential scale work and might recommend techniques more suitable for highways and commercial construction – with budgets to match.
Lex says
Soils Report Shows Expansive Clay
I am looking at a home with a soil survey that reports shrink-swell clay. The slope of the property allows any water to drain away from the foundation. What can I do to make sure that I won’t have structural problems down the road? My concern is the backyard deck and the foundation of the home.
buildingadvisor says
The short answer is that, if the expansive clay soil stays at the same moisture level year-round then it will remain stable. However, if the moisture level changes it can shrink or swell significantly and cause a lot of damage to the structure. The fact that you have good surface drainage away from the foundation is certainly helpful. But I wouldn’t count on that alone to control subsurface soil conditions. For example, if you have a wet season and a dry season in your part of the country, that could cause problems. One big storm could potentially saturate the soil around your foundation.
Building on this type of soil requires extra expense and special expertise in building on expansive clay. Personally, I would not build a house on this type of soil without a soils engineer specifying the foundation plan and a contractor with a proven track record building on expansive clay. You would also want some type of extended warranty on the structure since problems may not show up for several years – and they can be very costly and difficult to remedy.
Read more on Expansive Clay Soils
Joy says
Water Pooling Near Patio
I’m considering buying a home and have already negotiated what issues the seller needs to fix. However, I was looking over the home inspector report again, re: slope and drainage issues. The report says:
“Back yard is higher than the home’s foundation and the downward slope to the patio area suggests water pools at the patio. This may be why there is minor wood rot at the bottom of some jambs and doors. Proper measures should be taken to divert water from pooling at the patio slab to prevent or reduce wood rot in the future in these areas.”
Should I go back to the negotiating table and see if seller will fix it or is this a minor issue that I can do after the closing ?
buildingadvisor says
If the home is at the bottom of a large slope, and significant quantities of water are directed toward your home during wet weather, then this can be a significant problem leading to basement leakage, high humidity levels in the home, and the sort of exterior wood decay you are seeing. It is also possible that the decay is a result of “splashback” from roof runoff (if there are no gutters) or snowmelt sitting next to the house.
On the other hand if it is a small sloping area, and your climate does not get a lot of snow or rain, then it is certainly less of a problem.
If there are no signs of basement leakage or other household moisture problems, then your problem is probably not too difficult to manage. If possible, you will want to regrade a portion of the yard to direct water around and away from the house. Ideally, you want the finish grade to slope away from the house at a slope of about 6 in. over 10 ft. Any wood trim or siding on the house should be a minimum of 8 in. above the soil.
If it is not practical for you to re-grade in this way, which sounds like the case here, you can often direct surface runoff away from the house by using a shallow ditch called a “swale” or with a small gravel-filled trench – with the addition of a perforated drain pipe buried in the gravel if needed.
The important thing is to come up with a plan to intercept the water and move it to a place where it can be safely absorbed back into the soil or drain into a storm sewer without causing problems.
Unless the house is experiencing major leakage problems, my guess is that this would not be too expensive a fix. If you’re concerned, make your offer contingent on getting a suitable bid to fix the problem. Best of luck with your purchase!
Sheryl says
Lot Becomes Mud Puddle After Rain
We purchased a lot from a builder who is also building the house on it… The lot used to be the parking lot for the model homes next to it. We have noticed and worried about the drainage of the lot since it has rained a bit and the water puddles in the back and side and has taken a few weeks to become a mud puddle. I am worried that it is going to add costs to our budget that wasn’t seen ahead of time. Should we get out now?
buildingadvisor says
I assume that the lot you purchased is only rough-graded at this point for purposes of construction. The final grading should take care of the surface drainage issues and this should be part of the builder’s plans, assuming he is a professional and conscientious builder.
At this this point, I would simply meet with the builder, express your concerns and ask what his plans are for site drainage. If these are not already written into the plans and/or specifications, you might want to add these as an addendum to the specifications. If you trust that the contractor will do what he says, and he assures you that the site will drain properly and not generate mud puddles, then you may be OK relying on his verbal commitments. However, it’s certainly preferable to get this in writing.
If he does not have a good answer to your question, or wants to charge extra to provide a suitable drainage plan, then you need to decide whether to pay extra or get out now, if that’s an option for you.
In any event, it should be made clear in the plans and spec what you are getting in terms of finish grading, topsoil, grass seed or turf, and plantings, if any. If it’s not clearly spelled out, get it all in writing so you you know what to expect when the project is completed. Misunderstandings about what is included and excluded from the “scope of work” are the source of many disputes between owners and contractors. A clear and well-detailed set of plans and specs helps avoid these kinds of misunderstandings.
To avoid other misunderstandings like this, a good question to ask is: What additional costs should I anticipate during and after the project to complete the home? To avoid costly surprises, see the list of often overlooked expenses in Estimating Land Development Costs.
Related links: Building Specifications Scope of Work
Best of luck with your new home!
Edward Knight says
Pooling Water Floods Septic Tank
We purchased land from a local builder who also built our home (he is no longer in business). When it rains the water pools around and under the house and recently were told by a county building inspector that our home was built in a “bowl.” Every time it rains the water from the homes on either side of us drains toward our home causing our septic tank to fill. The problem also affects the total water system within the home; toilets don’t flush properly, water bubbles up through the sinks, shower, tubs, and we can barely use the washing machine or dishwasher. What can we do to make our situation better?
buildingadvisor says
With you house sitting at the bottom of a depression or “bowl”, you could have a real challenge with managing surface water. Naturally runoff from the surrounding property will drain into the bowl under and around your house and septic system.
The goal when grading around a new house is to have the soil around the foundation slope away from the house for at least 10 ft. with a slope of about 5% (6 in. in 10 ft.). Where this is not feasible, more creative approaches are required to direct the water away from the house.
The simplest approach for problem sites is often a wide ditch called a “swale” which can catch runoff and direct it to a suitable area, which might be a paved street near a storm sewer inlet, or a wide area of grass or vegetation that can absorb the amount of runoff generated. You don’t want to dump it on a neighbor’s lawn, a sidewalk where it might freeze, or an area subject to erosion. Sometimes a large “rain garden” is created for the purpose of soaking up the water. However, if your lot is the lowest point around, it’s not clear where a swale would drain to.
A more promising approach for you might be “curtain drains,” which are ofren used to intercept water flows on a slope and to carry the water to a suitable outlet. Curtain drains (also called “interceptor drains”) are trenches generally 18 – 48 in. deep and 18 -24 in. wide. The trench is wrapped on all sides with filter fabric to prevent silting, and filled with course gravel or crushed stone. It’s best to line the downhill side of the trench with min. 6-mil plastic to further retard it flowing toward your house and septic system. Also you should bury a perforated drain pipe near the bottom of the trench to provide good water flow. The trench and pipe should slope downward (1% min. grade) to an outlet in a safe drainage area.
You can view a diagram of a curtain drain courtesy of NDS,Inc., which publishes an guide to building site drainage.
Finding a suitable drainage area may be difficult given the amount of water you are dealing with and the fact that your home is sited in a depression. Your best bet may be to end each curtain drains in a large drywell that can store the water temporarily and allow it to slowly discharge back in the soil far enough from your home and septic system. If necessary, you can pipe the water to the drywell with solid (non-perforated) drain pipe. As a last resort, you could collect the water in a suitably sized concrete or plastic sump and pump it to a municipal storm drain or other suitable location.
While you are addressing surface drainage from the surrounding properties, don’t forget your own rooftops. Use gutters and downspouts and make sure the water is conducted safely away from the house and septic system.
If you are still having occasional flooding of the septic tank after completing the drainage work, you might want to consider installing a backflow valve or backflow prevention device (BPD) in your main sewer line. This should prevent the backups you are experiencing. These are expensive and do not offer 100% protection against backflows, but should work properly in most cases. You can read more about these at our sister site Inspectapedia.com.
Best of luck with your situation. I’d strongly recommend spending a couple of hundred dollars to get a plan from an engineer (civil or geotechnical) before installing an elaborate system. A top-notch excavation contractor may be able to design a workable system, but unless they guaranty success, I’d want the input of a professional engineer here.
Kelly says
What is “High and Dry” Site?
Hi, I have a question, what does “high and dry” mean in respect to a residential lot. Also, what are the advantages and disadvantages of a high and dry lot? Thank you!
buildingadvisor says
Hi Kelly. “High and dry” is not a technical term. It’s a marketing phrase to indicate that the land sits well above the water table and has good natural drainage. This means it should be free of marshy areas, wetlands, or other wet areas that can cause problems with septic systems and basement leakage, not to mention noxious insects. So “high and dry” is a good thing, unless you’re a mosquito or black fly, that is.
Keith Cobb says
Recommended House Elevation From Drainage Ditch
Is there any recommendation for how high the grade of a home needs to be above an existing drainage ditch. Of coarse, it cannot be below the drain age ditch but what is the typical elevation above the ditch to get flowing water?
buildingadvisor says
Many basement water problems result from rain and snow melt that pools around the foundation and then runs down the foundation wall into the basement or crawlspace. The best solution is to slope the finish grade away from the house so surface water drains safely away. The general rule of thumb is to provide a grade of 1/2 in. to 1 in. per foot for a minimum of 6 to 10 feet on all sides of the house. That’s a drop of 5 to 10 in. over 10 ft. This slope should be adequate to get the water safely away from the foundation into a drainage ditch, swale, storm sewer, or level lawn area.
While it is a good idea to backfill around the foundation with granular fill such a gravel or crushed stone, the top foot or so should be a dense, non-permeable soil such as clay (with 6 in. or so of topsoil above for plantings). This will help move the water quickly away from the foundation.
Larry Foster says
Evaluating Flat Site
I own a 3/4 acre lot. I went to the city to see if it was in a Critical Area (regulated wetlands) and it is not. The lot is really flat. Do you suggest a “perk test” as a reasonable first step to determine soil condition? It is winter time here in the Northwest but can find a contractor to dig some perk holes? Any advice is appreciated.
buildingadvisor says
Before spending money on a perk test, I would have a quick meeting with the town’s building and zoning department. Tell them what you are planning to build and ask if they foresee any regulatory problems. Then, assuming that you are planning to install a septic system,check with the town’s health department to find out the requirements in your area for a perk test and deep hole test. Each jurisdiction has its own rules about who can conduct the tests and what time of year, as well as test procedures and criteria for passing.
If your site passes the test, you will be able to install a standard septic system with a conventional leach field. The deep hole test will also give you information about the soil types on your land which can help with foundation design.
Unless the ground is frozen solid, you should not have any problem conducting a test this time of year. You can read more at the following links: Soil & Perc Testing Best Time of Year for Perc Test