Plan an ICF Build
The cost math, the level-footing rule, and the pour-day checklist that ICF construction runs on.
How a House Meets the Ground: Footing, Foundation, Sill Seal, Mud Sill
The load path runs from roof to footing: the footing's wide footprint spreads the house's weight into the ground, rebar ties the poured foundation to it, a foam sill seal on top blocks moisture and air, and the anchor-bolted mud sill is the wood everything else sits on.
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The Problem
"Foundation" gets used for everything below the first floor, but the bottom of a house is four distinct layers with different jobs. Knowing which is which is what makes foundation cracks, sill rot, and anchor questions possible to even talk about.
The Main Types and When to Use Them
Footing. The wide concrete pad at the very bottom. It carries the entire load of the house and disperses it into the ground — the wider footprint is what resists settling. Rebar is set sticking up out of the footing before the next pour.
Foundation. Poured on top of the footing, locked to it by that rebar. It can be a short stem wall, a crawl space, or a full basement — in every case its job is the same: collect the weight of floors, walls, and roof and transfer it down into the footing.
Sill seal. A gasket layer laid on top of the foundation wall. It blocks moisture wicking up into the wood, acts as an air barrier, and keeps mud out of the house during the build.
Mud sill. The first wood in the house: a board wrapping the entire perimeter on top of the sill seal. Band boards and first-floor joists sit on it. It's fastened down with anchors cast into the foundation — usually J-bolts the foundation crew sets in the wet wall, or wedge anchors added after — which keep the sill from shifting, which keeps the walls above from moving.
Pro tip: The whole stack is one load
path: roof to walls to joists to mud sill to foundation to footing to
ground. When you're evaluating any structural change — removing a wall,
adding a beam — the question is always where the load rejoins this
path.
Electrical, plumbing, and structural work may be regulated where you live — check local code before you start, and note that a permit may be required. More in our disclaimer.
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