In those parts of the country where the frost line is deep and basements are the norm, foundations are typically built by specialty subs, who can afford to stock the necessary forms because they use them every day.
Of course, there are shallow frost-protected monolithic slab foundation methods for cold climates, that expand on simple slab edge insulation but we're not going to talk about that here.
But in parts of the country where the frost line is shallow or the ground never freezes it’s not uncommon for contractors to form and place their own shallow foundations—as is being done in this video shot by Dave Osland.
The house is being built near the coast in Northern California, where the ground never freezes and stem wall foundations are common. Stem walls are short—typically just tall enough to create a crawl space under the floor joists.
Osland uses an old-school method to place the footing and walls in a single pour.
How it’s done:
- The footing is contained within a trench above which forms are supported and braced by vertical and diagonal 1x2s.
- The walls are formed with 2x8 lumber stacked on edge.
- Footing is placed first using very stiff concrete.
- Stem wall is placed second, using wetter concrete so as not to leave voids.
- After the foundation is stripped the 2x8 form lumber is “recycled” for use as floor joists.
My house was built in 1965 and I can tell its stem wall foundation was built the same way—with many of the floor joists having first been used for forms.
Osland does some things that wouldn’t have been done in 1965, like using more rebar and installing the many j-bolts and hold-down bolts required by today’s seismic codes. I like how he uses drywall screws instead of duplex nails.
Using aluminum foil to protect the threads on the bolts is a nice touch.
Learn more about high-performance foundations in the Building America Solutions center.