This is a house I designed and built in 1978. For the most part it looks the way I built it, except for the big wrap-around deck and the addition to the back of the home.
On a recent adventure to see how some of my wood foundation houses are behaving (after more than 35 years), I stopped and introduced myself to the current owners of the home. They were very gracious and were happy to show me some issues with the home and it gave me a chance to help them with some questions they had about the home.
They had experienced some flooding of the basement space and were told they needed to install a perimeter drain around the interior of the foundation–including a sump pump. While this is a common “remedy” for concrete foundations, it should never be necessary for a properly installed wood foundation. Any water intrusion (that could not be accounted for by penetrations of the foundation like drain pipes etc) would almost have to be from failure of the installed drainage system.
A wood foundation sits on 12” of pea gravel with perforated drains to collect the water and drain it away to day-light.
Because the perforated perimeter drain continues out of the stone after it exits from under the slab, and slopes downward toward the termination of the drain at daylight, water typically would never be expected to reach the interior perimeter drain installed higher up in the stone. If the day-lighted drain becomes blocked or crushed for some reason, water can fill up the stone under the concrete slab and then come up around the slab and into the basement space.
A recommendation to install an interior drain by cutting away the floor is a very expensive and unnecessary undertaking.
I can’t help but wonder what the installers of the interior system thought when they found my installed perimeter drain under the slab. Did they use? Remove it? The correct repair would have been to figure out why the stone was not draining and fix it.
A little research about how wood foundation systems function could have saved the home owners considerable amounts of money.
Back to the addition to the home.
Note how the roof overhang on the addition does not extend past the wall as much as my design. See how the shorter overhang results in much more weathering of the siding? Large overhangs on homes can serve many functions, including protecting the siding and helping to minimize solar gain in the summer time.
By Charles Buell, Real Estate Inspections in Seattle
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