Steps for Constructing a High-Performance Concrete Slab for a House

Journal of Light Construction

Concrete is one of the most durable materials we can build with. That makes it ideal for foundation slabs. But it’s also one of the most thermally conductive materials we have.

In this story, architect and builder Chris Laumer-Giddens, a principal of LG Squared in Atlanta, explains how he detailed the slab foundation for an off-grid project in the North Carolina mountains. Our goal was to build the five slabs for the compound so that they would last virtually forever, and to integrate them into buildings designed to be self-sufficient for energy. Our strategy was to isolate each slab from ground moisture with a vapor barrier and to thermally isolate it from the ground with insulation—essentially, keeping the slab within the conditioned building enclosure.

Treated this way, and with concrete specified and placed according to known quality standards, there’s no reason each slab shouldn’t last for many generations beyond the lifetimes of the original owners. And especially by insulating the critical slab edge, where the greatest potential for heat loss occurs, we could meet the project’s goals for energy self-sufficiency.

Above is a version illustrated by Tim Healey of the author’s slab detail from a wood-framed house in Marietta, Ga. Here, the author has used a bent metal termite-control flashing integrated into a sub-slab Pango Wrap termite-control vapor barrier membrane. The slab and the wood structure are all contained within the conditioned envelope of the building.

To read the rest of this story along with step-by-step instructions with photos from JLC click here.