Question 1

What size footings do I need for a house?

Accepted Answer

Typical residential foundation footings are 16 to 24 inches (40 to 60 cm) wide and 8 to 12 inches (20 to 30 cm) deep. A 1-story wood frame house with 2x4 walls needs at least 16 inch wide footings; a 2-story brick veneer house needs 20 to 24 inch wide footings. Always refer to the IRC (International Residential Code) footing tables and your soil bearing capacity, and have a structural engineer size footings for anything larger or on poor soil.

Question 2

How deep should a footing be?

Accepted Answer

Footings must extend below the local frost line to prevent heaving damage. Frost depth varies: 0 inches in south Florida, 12 inches in mid-Atlantic states, 32 to 42 inches in the northern US and most of Canada, and 60 to 80 cm in much of Europe. Even in warm climates, footings should be at least 12 inches (30 cm) below grade and bear on undisturbed soil or compacted fill.

Question 3

How do I calculate concrete for a strip footing?

Accepted Answer

A strip (continuous) footing volume = length x width x depth. Example: 50 linear feet of footing that is 20 inches wide and 10 inches deep equals 50 x (20/12) x (10/12) = 69.4 cubic feet, or 2.6 cubic yards. In metric: 15 m x 0.5 m x 0.25 m = 1.875 cubic meters. Add 10 percent waste for irregular trench bottoms, giving 2.86 cu yd or 2.1 cu m.

Question 4

How much rebar is needed in a footing?

Accepted Answer

A typical residential continuous footing uses 2 to 3 horizontal #4 or #5 rebars running the length of the footing, with #3 transverse ties every 16 to 24 inches. Pad footings for posts and piers typically use a grid of #4 or #5 rebar at 12 to 16 inch spacing in both directions. The ACI 318 code requires at least 3 inches of concrete cover over rebar for footings cast against earth.

Question 5

What is the difference between a footing and a foundation?

Accepted Answer

A footing is the wide, shallow element at the bottom that spreads building loads onto the soil and prevents settling. A foundation is the overall structure (footings, walls, slab) that supports the building above. Footings are always part of the foundation system. A house may have continuous strip footings under perimeter walls, plus pad footings under posts and piers inside.

Question 6

Can I pour a footing and wall together (monolithic)?

Accepted Answer

Yes, a monolithic pour combines the footing and a short stem wall (or slab edge) in one continuous pour. This is common for slab-on-grade homes in warm climates and is faster and cheaper than a separate footing and wall. However, in cold climates where footings must be below frost, you typically pour footings first, then separate foundation walls with formwork.

Question 7

Do I need to reinforce pier or pad footings?

Accepted Answer

Pad footings under posts typically need a bottom grid of #4 or #5 rebar at 12 inches on center each way, with 3 inches of cover. Small deck pier footings (under 2 feet wide) may only need 2 to 3 bars in each direction. Always verify with your local code and structural plans. For uplift or seismic zones, footings may also require vertical dowels tying them to the column above.

Wall Type	Footing Width	Depth
1-story wood	12 in / 30 cm	6 in / 15 cm
2-story wood	16 in / 40 cm	8 in / 20 cm
Brick veneer	20 in / 50 cm	10 in / 25 cm
Solid masonry	24 in / 60 cm	12 in / 30 cm

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