Breaking ground for a new home was a dream come true for a Kentucky landowner. The dream turned into a nightmare, though, when the topsoil turned into bedrock. Blasting away enough stone to make room for the foundation also blew a $12,000 hole (in 1986 dollars) in his building budget.
A Rochester, Minn., couple's home had reached the framing stage when the middle of the basement floor began to buckle and collapse. A hidden sinkhole was to blame.Another Midwestern homeowner insisted on placing his home on a slope, and the soil collapsed. Now, he has to find a way to repair the back of his house, currently a full foot lower than the front. An 8-inch crack runs along one side, and support columns have crumbled.
Add to this list the California hillside homes that have been washed off their perches, and sinkholes in Florida's sandy soil that swallow entire houses - both almost annual disasters reported on the evening news. The real tragedy in all these stories is that these problems can often be anticipated or avoided with a little preparation.
Problems begin to surface when overeager home shoppers assume that buying acreage differs little from buying a subdivision lot. City subdivisions are governed by municipal codes that often don't apply to rural areas.
Lots in subdivisions benefit from the research and scrutiny of road, to sewer and electrical contractors. To satisfy the bank's concern for its loan money and the city's concern for public safety, the developer and contractors must submit their property to a flurry of tests that ensure the land is suitable for houses.
Acreage sites don't offer such reassuring inspections, so pull your eyes away from the view and get to work discovering what's beneath the surface.
The soil and the environmental history of any tract of land can be difficult to uncover, but help is available. The range of resources is as diverse as the soil itself. Some of this information will apply to local geographic areas; some to your specific site. You'll need to know both because soil properties can change greatly within short distances. Some are seasonally wet, prone to flooding, or mask high water table that would constantly channel water into a home's sump pump. Some are shallow to bedrock, or are too unstable to support building foundations or roads.
Clay-filled or wet soils are poorly suited for septic tank absorption fields, and a high water table might bar basement or underground installations.
None of these problems is obvious to the untrained eye of the homebuyer, and yet the first and easiest step is to inspect the site yourself. Walk the entire property when it's dry and again after hard rain to note how the land reacts. With personal observations in hand, tour the neighborhood. Explain that you're considering buying nearby and ask the neighbors if they can share with you any land or building problems common to the area.
"Never underestimate the information available from the neighbors," advises Kentucky architect Tom Wilmes. "People who have lived in the area for a long time tend to know about the problems."
If you have questions at this stage, one place to turn for answers is the Natural Resource Conservation Service (formerly the Soil Conservation Service). Most states have an office in each county, or you can check your local phone directory's federal government listings for the office in your state.
The Natural Resource Conservation Service publishes a Soil Survey of your area. This large book, free for the asking, maps each area or evaluates how specific soil types will perform under various building or conditions. The survey rates the soil in numerous ways, but the categories most important to the potential land owner are the building, sanitary facilities (septic tanks and absorption fields), and water management tables.
Local conservation officers will visit the site and interpret the charts free. But since their maps only examine the soil to about 60 inches deep, a clean bill from this inspection means it's time to contact a geotechnical civil engineer to conduct a more in-depth analysis.
Check the Yellow Pages under "engineer." If geotechnical, or soil, engineers aren't listed specifically, try the "consulting or soil, engineers" listing and ask if the company has a soil or geotechnical specialist on their staff.
If you're investing a huge amount of money in a home, you don't want to take anything for granted, notes Harry Al-len-der, a geotechnical civil engineer in Iowa. We see more and more lending agencies requiring this type of professional advice for people building $400,000 and $500,000 homes.
Geotechnical civil engineers offer many commercial development building services. The most common residential service is soil boring: taking samples from several spots on the proposed building site.
The engineer extracts a sample that runs at least 5 to 20 feet below the house footings. A rule of thumb is to sample at least twice as deep below the footing as the footing is wide to ensure that the soil can support the foundation. Analyzing the type of soil from 20 feet deep helps predict possible settling and water problems.
It takes someone who knows what to expect from local geology to accurately access the sample and provide a useful report, advises professor Richard Handy, author of "The Day The House Fell," a guide to site selection and home building published this spring by the a guide American Society of Civil Engineers.
The testing and subsequent report for a residential property averages about $1,500 in most parts of the United States. That may seem expensive, but sinking homes and backed-up septic tanks cost much more to repair.
Geotechnical engineers also offer a "phase one environmental assessment" that developers often use to satisfy their loan requirements. This report researches the land's environmental history by studying previous owners and previous uses. Any hint that your site once housed a chemical-related or toxin-handling commercial business, or the neighborhood dump, should prompt an environmental study.
"Just because there is a problem doesn't necessarily mean you can't build," reminds Handy. "You must simply be aware of how to build properly before you begin." From finding a more suitable site, to blasting out several layers of bedrock, solutions will often hinge on striking a balance between what you want and what you can afford. Targeting and studying the problem before you build helps avoid an unexpected crisis and unnecessary financial burden once it's too late to halt construction. It also shifts your role from victim of the problem to manager of the solution.
Types of soils - and their drawbacks
If you're considering buying a lot for a new home, an important, but often forgotten consideration is the soil.
The perfect soil probably doesn't exist. Each type has flaws, but some have fewer flaws than others. Be aware of the basic soil types and how they can affect your foundation.
Sand: This is often considered the most desirable soil type, but avoid it if a survey or report indicates dune sand. This type of sand is softer than most and can compact, allowing the house to settle.
Silt: Finer than sand, silt is very susceptible to frost heave. Wet silt loses its structure and compresses. As the soil becomes more compact, lt foundations sink. "Loess" is a common silt soil.
Clay: Many clay soils soak up moisture and expand, raising a home's foundation unevenly.
Shale: Another expansive soil, shale is also susceptible to landslide lt problems when horizontal slabs separate and slide off each other.
Limestone: Sinkholes are part of limestone formations. The problem is lt not the holes you see but the ones that haven't yet settled.
Bedrock: An excellent base, but excavation costs run about 10 times more than soil if the bedrock interferes with your basement.
Fill soil: At some point, for some reason, someone trucked in extra dirt to either level off or cover up the existing terrain. If it isn't an engineered fill - one that recently passed compaction tests - then beware. There may be a problem buried under the fill. Your geotechnical civil engineer can determine the condition of the fill and what hides beneath it.
What questions to ask
Until you have the answers to the following questions, you're not ready to hand over your money for a new acreage site. Don't rely on the real estate agent or the current land owner to provide the answers to the following questions without written documentation. Rely instead on impartial experts to help in your research.
-How is the land zoned?
-Are water and sewage lines accessible?
-Has a percolation test been performed?
-Is a soil analysis test result already available?
-Does the lay of the land support water runoff?
-Is the slope conducive to running a sewer line?
-Can you find results of subsurface investigations describing soil composition/compaction and unusual site conditions such as rock ledges or underground springs?
-Is a current legal survey available?
-Are there any easements?
-Has the land been declared a wetland?
-Are there any indications that water may stand on property part of the year so that the land could later be designated as a wetland?
-Does the buyer assume all water rights?
-Are there any landfills nearby?
-Are any historical aerial photos available? Do they show any past use that indicates hazardous material near the land?
-Do any government toxic site lists identify this property or others within 2,000 feet?
-Is there any evidence of underground storage tanks?
-Is the land along an active fault line?
Who else can help
Other resources for information on the soil, history, and previous use of a proposed building site include:
- The nearest city engineer and building inspector. Their tenure use generally indicates how much they know about the areas surrounding the city.
- Sanborn maps, probably available at the local library. Fire departments and insurance companies rely on Sanborn maps to indicate where companies store chemicals. Older maps can often indicate if a building that housed chemicals once occupied a specific site, possibly contaminating the land.
- City directories indexed by address. Back issues may be especially helpful.
- Geography instructors from local schools and state universities. Local landscapes are often their classroom projects, and they know them well.