Concrete Footing Size Chart (Width & Thickness)
Part of Concrete & Masonry
Quick answer
For typical soil (about 1,500–2,000 psf), a continuous strip footing is roughly 12 inches wide for a one-story house, 15 inches for two stories and 18–23 inches for three — all at least 6–10 inches thick. Soft soil and heavier loads need wider footings, and the bottom must sit below the local frost line.
A footing spreads a wall or post load out over enough soil that the ground won't settle under it. Two things size it: how much load it carries (stories and roof) and how strong the soil is (its bearing capacity). The chart below covers conventional light-frame houses on average soil.
Strip (wall) footing sizes
| Supported load | Footing width | Footing thickness |
|---|---|---|
| 1 story | 12 in | 6 in |
| 2 stories | 15 in | 7 in |
| 3 stories | 18–23 in | 8–10 in |
| Soft / clay soil | +3–6 in wider | +2 in |
Column & post footing pads
| Use | Square pad | Thickness |
|---|---|---|
| Deck / porch post | 16 × 16 in | 8 in |
| Light beam post | 24 × 24 in | 10 in |
| Heavy / 2-story post | 30 × 30 in | 12 in |
The rules behind the chart
- A footing is usually twice the width of the wall it supports, and at least as thick as it projects past the wall on each side.
- Minimum thickness is 6 inches; never thinner than the wall above.
- The bottom of the footing must be below the frost line — 12 inches in the south to 48+ inches up north.
- Weaker soil needs a wider footing to spread the same load; always confirm with local code or an engineer.
Once you have the width, thickness and total length, use the concrete calculator (slab shape) to get the cubic yards and bags, and the rebar calculator to size the reinforcing steel.
FAQs
How wide should a footing be?
About twice the thickness of the wall it carries — commonly 12 inches for a one-story house and up to 23 inches for three stories on average soil. Wider on soft soil. Local code governs the minimum.
How thick should a concrete footing be?
At least 6 inches, and never thinner than the footing projects out past the wall on each side. One- and two-story homes typically use 6–8 inches; heavier loads use 10–12 inches.
How deep does a footing need to be?
The bottom must sit below the frost line so freezing soil can't heave it — that's roughly 12 inches in warm climates and 48 inches or more in cold ones. Check your local building department for the frost depth.