Sound Smarter on the Jobsite: Footing vs Footer
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It's "footing" not "footer," but...it's kind or a regional thing. I learned to build in Virginia, and everyone said footer. So what's a footing/footer? It's the "foot" at the bottom of a foundation wall that increases bearing surface.
Here is a continuous footing w/ the start of a CMU stem wall, and some column footings. Same concept in both: load is coming from above (aka the weight of the building and everything/everyone in it) and headed to the ground. If the wall or column landed directly on the ground, it would push into the ground instead of sit on top. Think of a footing like a snowshoe, spreading the weight of a person out over a larger area so the person doesn't sink in the snow. Same idea. The size of a footing depends on the loads and the soil conditions.
Footings are often concrete, and can be as crude as a trench dug in the soil and formed without formwork. They can also be extremely intensive, like piles. (Piles are not technically footings, but serve a similar purpose - dispersing the load at the ground.)
This is why having a geotech/soils report is *vital* early in the feasibility phase. Soil conditions and foundation types can have massive impacts on what can be built, costs, complication, etc. It's one of our first questions to a developer or owner.
Many foundations on homes and small multifamily that we work on in the Boston area don't have footings. The foundations are just giant granite blocks or even large rubble that bears directly on the ground. When I look at a property with a client, one of my 1st stops is the basement, to see what we're dealing w/. No footings can make a reno more complicated or can mean the bldg has settling issues. The fix is...expensive: we lift the house up, rip out the old foundation, pour a new one, and set the house back down.
We don't always have to go that far to fix things, and often these rubble foundations are solid, but...they didn't exactly have geotech reports 100 yrs ago, so they were often guessing about conditions, or they didn't care (bad builders/developers/architects are not a new thing!)
Concrete footings have rebar embedded in them, to resist tension. Concrete is amazing in compression, but bad in tension. Steel is great in tension, so we add steel rebar ("reinforcing bar") to areas of the footing that experience tension.
Here's what I mean. When a footing takes load from above, it "smiles" - it pushes the center of the footing. This places the bottom of the footing in tension, bc it is trying to lengthen, and the top in compression, bc it is trying to squish. So we put rebar at the bottom, to resist that tension.
Concrete is poured in sections, and the joint bw sections isn't structural. The rebar connects the dots. In this CMU pic, vertical rebar has been cast into the footing and reaches thru the CMU cavities, which will be filled w/grout (liquidy concrete) to tie everything together. Rebar is a whole 'nother thread, but it really does matter to get it sized and placed correctly. Anyone who has tied rebar in the field for days on end, or reviewed a rebar shop drawing/submittal package knows....it's a ton o' fun. But very important!
Footings need proper drainage and waterproofing. Concrete wicks moisture like crazy, so it's important to get those details right. You gotta put the footing drain at the *bottom* of the footing, not at the crook, for example. And you have to surround it with stone, not soil.
So how do you know how to size a footing properly? If it's a single family, building code has parameters for builders to follow, and an architect or structural engineer is not always needed (depending on jurisdiction). If it's anything other than a single family, you need an architect and/or structural engineer. A SE will be thinking very specifically about the engineering, while an architect will think about how those engineering decisions affect usability, space, and other code considerations.
OK, that's it! As usual, this is a quick explainer of basic concepts, and doesn't take into account the many varying conditions that exist. And go ahead and say "footer" if you want, some people might get mad, but I'll know you're from the south.
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