Footing vs foundation wall: what it means on an inspection
A footing is the wide base, usually concrete, that spreads a building's load over the soil. The foundation wall stands on the footing and carries the load of the framing down to it. The footing is sized for the soil, and the wall is sized for the height of the earth it holds back and the load above.
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How to tell them from each other and what to check
- Find the base. The footing is the widest part, buried below the wall. It is usually poured first, in a trench or a form, and the wall is built on top.
- Check the bearing surface. A footing must bear on undisturbed natural soil or on properly placed engineered fill. Loose, soft or backfilled ground under it is a problem that no amount of concrete fixes.
- Check the depth. Footings generally go below the local frost depth, which the jurisdiction sets. Where soil freezes, a shallow footing can heave. Ask what the local frost depth is before you judge one.
- Check the size. Footing width and thickness come from tables that depend on the soil's load-bearing value and the load carried, such as the number of floors above. The foundation wall's thickness, reinforcement and height come from a different set of tables.
- Know when each is inspected. The footing trench is typically inspected before concrete goes in, and the foundation wall before the soil is backfilled against it. The jurisdiction's list of inspections is the authority.
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Common mix-ups
- Footing versus foundation. Foundation is the whole system, footing and wall together. The footing is one part of it.
- Footing versus slab. A slab-on-grade is a floor. It may be thickened at its edge to form a footing, but a slab and a footing are different things.
- Foundation wall versus retaining wall. A foundation wall also carries framing load from above. A retaining wall only holds back soil.
- Wider footing is not a fix for bad soil. The width is calculated from the soil value. If the soil is weak, the design changes; the footing is not simply widened on site.
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Footings and walls on the B1
Footings and foundations are 16% of the B1, covered in Chapter 4 of the IRC. Expect descriptions of soil, depth or an inspection sequence, followed by a decision about whether the work can proceed. Treat the chapter as three jobs: soils and footings, foundation walls, and drainage and dampproofing. The B1 exam outline guide breaks the area down.
Practice it
Move up the stack with sill plate, which sits on the wall, and see where this area sits in the IRC chapters guide. Then read cripple wall for the wood wall that can stand on a foundation. The IRC terms glossary links every term page.
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Sources
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- B1 Residential Building Inspector Content Outline, International Code Council.
- 2021 IRC contents and 2024 IRC contents, International Code Council. Chapters are named, not quoted; open your own copy for the text.
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From the blog
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