Hold the concrete! Don't pour that foundation - nail it! Wood basements now found warm and waterproof

IT came as no surprise to those who know Sam McHose that he should start developing a town-house complex in this Iowa community soon after he retired from banking. But what surprised those familiar with his background was his choice of construction materials.

Mr. McHose, steeped in concrete and masonry traditions, managed the family brick and tile plant at one stage. But he elected to go the all-wood route - right down to and including the foundations!

His research had turned up some surprising facts about the modern, all-wood foundation: It is permanent, warm, waterproof, and all but immune to condensation problems.

``I've never walked into the basement of a wood-foundation home and found it musty,'' he says. Imy, his wife and partner in the 28-acre development, agrees. She adds that she's walked into quite a few of these cellars in recent years.

In making the choice, McHose was also influenced by Larry Krupp, a contractor. With some temerity, Mr. Krupp put in his first wood foundation 11 years ago and his last concrete one in 1983.

``For the past five years, I've put wood foundations into everything I've built,'' he says - and that includes a block of commercial offices.

What appeals to McHose and Krupp is confirmed by a growing range of homeowners and builders. The pluses for the permanent all-wood foundation are many, they say, and list them as:

Livability. The basements have the same feel and comfort of the above-ground section of the house. Because wood conducts heat away from the basement at a much slower rate than concrete, it is far less prone to clamminess and mildew problems in summer.

Energy efficient. For the same reason, the all-wood basement is less costly to heat in winter. The fact that the basement wall is the same stud-frame construction as the walls above the ground makes it a simple matter to incorporate insulation as well.

Simple to finish. With nailable studs already in place, plumbing and wiring are readily hidden, and gypsum board or paneling is easily nailed in.

Provides more living space. To be finished off, a conventional concrete wall foundation has to have a stud frame placed on the interior to accommodate the insulation and the paneling. Combine this with the fact that the wood foundation is marginally narrower than a concrete-block wall (though not necessarily less than a poured wall), and the additional living space becomes obvious.

To these pluses, builders add a couple more:

Speed of erection. Many builders say that a wood foundation can be in place in a day. While some elect to build the foundation from scratch at the site, others prefer to preassemble the panels in the workshop and truck them to the work site.

Ease of waterproofing. All concrete shrinks and consequently cracks in some places. But the wood foundation, using approved pressure-treated lumber, will not shrink and is readily waterproofed. Says Clarence Buerman, a builder in Cold Spring, Minn., of the permanent wood foundation, ``[It's] the only system we guarantee to stay dry.''

In brief, the all-wood foundation rests on a bed of crushed rock, the thickness of which depends on the characteristics of the surrounding soil. Generally, the more clay, the thicker the layer of rock. Besides supporting the house, the rock also acts as a drain to funnel ground water away from the house.

All materials must meet the standards laid down by the American Wood Preservers Institute, and each piece will be stamped to this effect.

Don't assume that just because it's green it's acceptable in a foundation. Codes demand that the plywood sheets be fastened with stainless-steel nails or staples.

The origins of the permanent wood foundation go back some two decades to the realization that they could be built. Effective, environmentally acceptable preservatives and the technology to thoroughly pressure-treat the wood throughout made them possible.

At the same time two needs spurred on the move: In Canada builders sought a system that would make construction possible at temperatures too low for pouring concrete - while in the United States, the Federal Housing Administration saw in wood the possible solution to that perennial housing problem, the leaky basement.

By testing the foundations in those warmer regions of the country where unprotected wood would rot or be eaten by termites within a matter of months, the validity of the concept was proved beyond doubt. The structures show no signs of decay or deterioration after accelerated aging - the equivalent of 30 years on a conventional building site.

Of course, nothing on this earth is permanent, and Fulton Dessler of the American Plywood Association is the first to agree. But he adds: ``We have no hesitation in saying that the [all-wood] foundation will last as long as the house that sits on top of it.''

The wood foundation is now approved by the major building code regulatory bodies and by those federal agencies associated with housing. Bankers, too, are happy with the technology, because the major lending and mortgage insurance institutions all accept it.

For Larry Krupp the conversion to the all-wood basement didn't come easily.

The concept that wood belonged everywhere except underground was too ingrained in him, he says.

``I attended several seminars, and I liked what they said. I could see why the system worked, but I was reluctant to take the step.''

But finally Krupp reckoned that the experts had to know what they were talking about.

``I took the plunge, and I've never regretted it,'' he comments.