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).
To determine the size of the footing, a simple formula is used: Structural Load (lbs) / Soil Capacity (psf) = Footing Surface Area Required (sq. ft.)
The minimum depth of footings below the undisturbed ground surface shall be 12 inches (305 mm). Where applicable, the requirements of Section 1809.5 shall be satisfied. The minimum width of footings shall be 12 inches (305 mm).
The minimum footing thickness should not be less than the distance the footing extends outward from the edge of the foundation wall, or 6 inches, whichever is greater.
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).
Except for monolithic slab-on-grade foundations, all exterior footings shall be at least 2 inches (51 mm) wider on each side than the wall resting on the footing and shall not extend past the wall more than the thickness of the footing.
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.
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. The minimum width of footings shall be 12 inches (305 mm).
Depth of Footings
Footings should extend to a minimum depth of 12 inches below previously undisturbed soil. Footings must also extend at least 12 inches below the frost line (the depth to which the ground freezes in winter) or be frost-protected.
According to an example cited on TATA Tiscon site, if a 3-storeyed building rests on sandy soil, it will require minimum 5.5x5. 5 feet to 6x6 feet footing size. Similarly, a 2-storeyed one requires 5x5 feet and single storied will need 4x4 feet footing size.
When measuring for where to place your footers, make sure that the holes will be square with your house and that they are are no more than 8-feet apart in either direction. This is a general recommendation to keep your deck as sturdy as possible.
The footing transmits the load into the soil. The lower the bearing capacity of the soil, the wider the footing needs to be. If the soil is very strong, the footing isn't even strictly necessary just the soil under the wall would be enough to hold the building up.
The minimum footing width is 12 inches. Calculation of footing size may result in a smaller footing but the code requires a minimum 12 x 6 or 12 inches wide and 6 inches deep footing. In addition, tables are based on the type of foundation.
1 part cement. 2 parts sand. 4 parts stone (aggregate by volume)
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.
You can look up the recommended footing size, based on the size and type of house and the bearing capacity of the soil (see the table above). As you can see, heavy houses on weak soil need footings 2 feet wide or more. But the lightest buildings on the strongest soil require footings as narrow as 7 or 8 inches.
The region and wind zone that you are building in will dictate what is required by your local state and county codes. Areas that are seismically active definitely require steel rebar in the footing construction.
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).
Use compaction whenever the soil is disturbed during construction or when it's used for fill. Compact disturbed soil beneath footings, slabs, basement floors, patios, garage floors, driveways, concrete steps and sidewalks. If a sand, gravel, or crushed stone base is used beneath a slab, compact it too.
The section on footings in Formwork for Concrete (ACI SP-4) says that when fabricated forms are omitted entirely and concrete is cast directly against the excavation, larger tolerances may apply. The book also suggests forming the top 4 inches when casting concrete directly against earth.
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.
Concept: For footing: i) The thickness at the edge shall not be less than 150 mm for footings on soil and not less than 300 mm for footing on piles. ii) The depth of the foundation should be a minimum of 500 mm.
The depth of the footing hole depends on the type of soil and the size of the building. The hole must be deep enough so that the footing is below the freeze line (the depth at which water in the ground freezes) and above any soft or loose soils. Once the hole is dug, the footing must be created.
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.