Block vs. Concrete
Q: Should we build a solid concrete or cement block foundation?
We're planning to build a house in a rural area where the local contractors use foundations made of cement block instead of the solid concrete we're familiar with. Which one should we use?
—June Krieg, Wildwood, Missouri
Tom Silva replies: What kind of foundation a builder uses is usually determined by practical matters: how far it is to the nearest concrete ready-mix plant, how remote the job site is, what the local foundation contractors are most familiar with, and your budget.
All things being equal, I prefer a well-poured, steel-reinforced concrete foundation because it's better at resisting the pressure of water, which can seep through blocks, or of soil, which can topple them. But when a job site is more than 90 minutes' driving time from a ready-mix plant, there's no way the cement truck will reach the site in time to pour a foundation. You'll have to look at other options.
One would be to install precast concrete panels, like those made by Superior Walls. We used them on the TV show at the Acton project houses. These insulated panels are delivered on a flatbed trailer and craned into place. All the joints are sealed with a heavy-duty construction adhesive. This option will likely be much more expensive than block.
If you decide to go with block, don't take any shortcuts. The footing should rest on firm, undisturbed soil next to an outside drain. And the wall should be thoroughly reinforced with rebar and waterproofed with a membrane—such as Cosella-Dorken's dimpled Delta sheeting—that lets water flow down to the drain.