How deep do house footings need to be?

Author: Dr. Heather Tillman III  |  Last update: Saturday, June 7, 2025

A minimum of 12”inches deep for all footings and the width will be determined by the amount of stories, 12” inches for a single story, 15” inches for a two story and 23” inches for a three story. This is based on a soil bearing capacity of 1500(psf).

What is the minimum depth for a footing?

❖ Footings are required to extend below the ground surface a minimum of 12 inches (305 mm). This is considered a minimum depth to protect the footing from movement of the soil caused by freezing and thawing in mild climate areas.

How do I know if my footings are deep enough?

The footing depth, on the other hand, is typically determined by the soil type and the extent to which you must dig before striking undisturbed soil. Still, we recommend that the depth of the footing extends to a minimum of 12 inches after you've hit undisturbed soil.

How thick is a normal house footing?

Required Footing Sizes

In most cases, a house should have a minimum footing of 12 inches wide by 12 inches deep, with foundations that are 8 to 10 inches thick. This should be enough to support house weight and resist lateral soil and water pressure.

Do footings need gravel?

Footings typically must extend below the frost line to prevent shifting during freeze-thaw cycles. Dig footing holes about 6 inches deeper than required. Fill the bottom of the hole with 6 inches of gravel and compact the gravel with a 2x4 or wood post.

How Deep Do Foundations Need To Be For An Extension?

How deep should a footer be for a support post?

Each deck support post must be supported by concrete footings. The size of each footing is determined by the tributary load imposed on it. See the diagram below for an explanation of tributary load. Footing must be dug down into undisturbed soil and to a minimum depth of 12-in below the finished grade.

What is the rule of thumb for concrete footings?

For every 2 feet of adjustment to the width of the house, add or subtract 2 inches of footing width and 1 inch of footing thickness (but not less than 6 inches thick).

How deep are normal footings?

Footings need to be 600mm wide x 1m deep minimum,in some cases depending on ground quality/type,proximity of large trees footings are required to be up to 2m deep.

What is the difference between a footer and a footing?

Footings are structural supports that are used in addition to a foundation. They help transfer the load's weight from the foundation into the soil. Footers are typically in direct contact with the ground, while the foundation is in contact with the footing.

What should be the depth of footing?

All foundations shall extend to a depth of at least 50 cm below the natural ground level. The minimum depth of footing on sandy soil is 0.8 - 1 m, for rocky soil, it is 0.05 - 0.5 m and for clayey soil, it is 0.9 - 1.6 m. The minimum depth of foundation for the load-bearing wall is 900 mm.

Do footings need to be perfectly level?

Even the best contractors occasionally have to build on a sloppy footing. Ian Geisler, a noted ICF expert who has worked on hundreds of projects across the continent, says that realistically a perfect footing is anything within ¼” of level. “If it's within ½”, then it's workable,” he writes.

How close can you dig next to house footings?

Can I excavate near my neighbour? Excavate within 6 metres of a neighbouring owner's building or structure where that work will cut a line drawn downwards at 45 degrees from the bottom of the neighbour's foundations.

What is the standard footing size for a residential building?

Footings shall be a minimum of 8 inches by 24 inches (203 mm by 610 mm) for houses two and one-half stories and less. The footings for a three-story building shall be 10 inches by 24 inches (254 mm by 610 mm).

Can footings be too deep?

First off: Why you need accurate footings calculations

If you make your foundations too shallow or too deep, there is a risk to the integrity of the build, and a danger that any reinforcement, be it mesh panels or rebar rods, is positioned incorrectly, leading to reduced tensile strength and load-bearing capacity.

What is the minimum depth of footings?

The minimum depth of footings below the surface of undisturbed soil, compacted fill material or controlled low strength material (CLSM) shall be 12 inches (305 mm). Where applicable, the requirements of CBC Section 1809.5 shall also be satisfied.

How thick is a footing for a house?

Footing thickness - 8 to 12 inches. Footing depth - varies based on frost line and soil strength (some footings can be shallow, while other must be deep)

What is the maximum spacing between footings?

According to the rule of practice, the minimum allowable rebar diameter in a footing is Ø12 and the maximum acceptable spacing between the reinforcement bars is 150 mm. In certain occasions, the footing may have a reinforcement wire mesh both at its upper surface (see following figures).

How deep and wide do footings need to be?

A minimum of 12”inches deep for all footings and the width will be determined by the amount of stories, 12” inches for a single story, 15” inches for a two story and 23” inches for a three story. This is based on a soil bearing capacity of 1500(psf).

How much does it cost to install footings?

The footings range between $10 to $15 per linear foot installed. This does not include the prices of the crawl space walls, only the price of the concrete foundation. The average concrete block wall adds another $6 to $7 per linear foot, for a total crawl space price per linear foot of $16 to $22.

What is the minimum thickness of footing?

In reinforced and plain concrete footings, the thickness at the edge shall be not less than 150 mm for footings on soils.

Can I use concrete deck blocks instead of footings?

Deck pier blocks are used in deck building as an alternative foundation to traditional footings. They are placed directly on the ground, and do not require digging or pouring. They come pre-formed with holes for attaching the posts of a deck, making it easy to install.

How long to leave concrete footings before building?

How long after pouring concrete can you build on it? Concrete curing is a vital process in the construction of your home. Typically, your foundation will have good resistance when it's 7 days old, be better at 14 and at it's best at 28 days. However, it's unlikely you'll want to wait that long.

What is the best concrete for footings?

C40. C40 concrete is a strong commercial grade concrete mix most commonly used in the construction of structural and support beams, footings and foundations, roadworks, and in agricultural use. Ideal for: Foundations for septic tanks, paving HGV parks and agricultural yards.

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