Learn what to consider when buying an earth-sheltered house, including tips for checking structural soundness and waterproofing, heating and cooling systems, and building code compliance, questions for the current owner, and conditions for purchase.
Earth-sheltered housing is no longer an oddity. In fact, even though the concept of underground dwellings has been popularized only over the past decade or so, thousands of subterranean homes exist today. Unfortunately (for the average house-shopper), much of the material written about earth-sheltered structures is directed to the professional, or to folks who are at least acquainted with the technical aspects of such construction. And that's why we decided to excerpt this chapter from A Practical Guide to Earth Sheltered Housing by Mary Rollwagen, Susan Taylor, and T. Lance Holthusen. The authors—whose consulting firm, TLH Associates, handles many of the public education programs of the University of Minnesota's Underground Space Association—have specifically directed their attention toward potential homeowners who don't want to build their own houses, but would prefer to have the task contracted or to buy an existing earth-sheltered structure. Such people, of course, need to be sure they're making a sound investment, as this is a venture in which mistakes can be very costly.
When most of us want to acquire a conventional home, we find it much quicker to buy an existing home than to build a new one. Most of the defects in a conventional house are reasonably discernible to average consumers.
Buying an existing earth-sheltered home is a different story altogether. Since earth-sheltered houses are so new, few have appeared on the market for resale. It is estimated, however, that somewhere in the neighborhood of five to six thousand homes had been built by 1982. In addition, some speculation homes are always on the market. In the future, then, consumers may increasingly enjoy the option of buying rather than building an earth-sheltered home.
If you should find an earth-sheltered home that is for sale at the right price and quite fits your needs, how do you judge the soundness of its construction? What should you look for in any earth-sheltered home you tour?
There is no way to probe inside the walls to inspect steel placement or even to ascertain whether the waterproofing system is intact on buried surfaces. Evidence of problems can often be observed in other ways, however.
Look inside the house. for these signs of leakage or structural problems:
On the outside of the house and up on the roof, look for these clues:
If there is an active or passive solar heating system, find out how it works. Has the system met the owner's expectations? Does it require frequent manipulation or repair?
Be particularly watchful of a wood- or coal-burning stove: Was it inspected when installed for proper distances from combustible surfaces, adequate insulation protection, and proper air intake and venting? Be sure the chimney stack is self-supporting and not holding any other weight.
Here is where the real purpose of building codes can be put to work for you. Your protection as a second owner, with no control over the initial design and construction, is better assured if codes were met originally. If no codes are in effect for the area, the use of an architect or a reputable builder would reduce your concern. Check the following:
The insurance question raises an interesting fact about many earth-sheltered houses. Some earth-shelter building companies and owners report that they have been able to negotiate lower insurance premiums than would be paid for similar but conventional homes, because the structure is less vulnerable to fire and storm damage. Several insurance firms have even announced lower rates, usually on the condition that the home was designed by a qualified professional. When inspecting a house for potential purchase, ask whether the plans for the house had an engineer's stamp of approval. Buying a structure that was not professionally engineered could be a risky business.
The National Association of Mutual Insurance Companies (NAMIC) has circulated a list of areas for concern to insurance inspectors considering the underwriting of an earth-sheltered home. NAMIC concluded that, assuming specific areas of concern are found to be satisfactory, earth-sheltering is "an insurable risk" if the following conditions are met:
1. The shelter is designed by an architect.
2. The plans are checked and an engineer's stamp of approval is included.
3. Building codes are followed and quality building materials are used by a reputable, qualified contractor.
4. Natural drainage and water table height are adequately determined.
5. The foundation drainage is properly installed.
6. Good waterproofing material is expertly applied.
7. The supplemental heat (wood/coal burner) is properly installed (air intake and venting). Adequate clearance between heating devices and combustible materials must be maintained.
These conditions are sensible ones for a potential buyer to investigate before making a decision.
A design professional may be more astute in spotting trouble than a potential first-time earth-shelter homeowner. Consider hiring an experienced earth-shelter architect or engineer to inspect the property for a couple of hours. Most professionals will charge an hourly fee for such a service—it will be cheap insurance against a possible $100,000 mistake.
Finally, do not rush into this "ready-made" decision any more quickly than you would leap into building a new home. Be sure this earth-sheltered house fits your program, is truly as energy-efficient as its owner or builder claims it is, appeals to your sense of aesthetics, and is located where you want to live.
Compromise, of course, but remember that you have the knowledge to have your dream house built if you still feel that is the better choice.
From A Practical Guide to Earth Sheltered Housing by Mary Rollwagen, Susan Taylor, and T. Lance Holthusen. Copyright © 1983 by Van Nostrand Reinhold Company, Inc. Used by permission.
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