Owner-Built Home & Homestead
(Page 2 of 15)
The purposes satisfied by the final form of the building will suggest the material to be used and the method of building construction. In regard to foundation, we need some awareness of soil properties in relation to building (weight, site drainage, freezing conditions, etc.). When due consideration is not given to the functional aspects of the foundation, one may suffer either extravagant waste or structural failure.
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On the one hand, one naturally reacts with horror at newspaper accounts telling of homes destroyed as a result of faulty materials or careless construction. It is not uncommon for foundations to settle, break away or slide during heavy rains when built on uncompacted fill. Mickey Mouse plumbing or electrical installations can also threaten the safety and health of occupants, as well as the building itself.
It is also shocking, however, to see tons and tons of unnecessary material go into a house. This material, and the labor required to place it, introduces long years of mortgage slavery. Who is to say which brings the greater personal hardship, the few jerry-built homes which may eventually end up in the bottom of some ravine or the many code-enforced, overbuilt structures that become 30-year millstones around the necks of unwary home owners?
The foundation of a house can be an unnatural depository for tons of unnecessary concrete. Instead of fundamental formulas and common sense designing in a foundation, it is usually a haphazard, rule of thumb, local and code-dictated practice that sets the pattern.
When the true function of a foundation is understood, its design in relation to soil conditions and climactic factors will, in turn, influence the form of the superstructure to be supported. A building foundation consists of two parts; foundation-footing and foundation-wall. The footing is a basic supporting element upon which the total weight of a building is distributed via columns or foundation-walls.
One of the foremost problems associated with footing design is determining the bearing capacity of the soil. For hardpan or very firm, welldrained soil, there should be not more than four tons of building weight for every square foot of footing area; for wet sand or firm clay, two tons; for soft clay or loam, not over one ton.
Frost line and ground water factors are two other items which determine the design and material chosen for foundation construction. The frost line along the northern belt of the United States varies from 4 to 6 feet in depth, and in most areas of the central United States it averages from 2 to 4 feet. Foundation walls must extend below these depths if danger of freezing is to be avoided (alternate expansion and contraction of the earth during freezing and thawing may heave the footing and damage the foundation-wall and superstructure). An alternative solution is to use a rock ballast similar to railroad beds under the foundation and floor, thereby insuring maximum drainage. Gravel filled trenches under the footing have also been successfully used for ground water drainage (a gravel bed will support 6 tons of building weight per square foot).
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