As a thumb rule, depth of footing of a free standing wall is usually 1/3 of its height to ensure stability. So for a wall of height 8 ft, its footing should be 2.7 ft deep.
Usually footings are located at depths of 1.5 to 2.0 meters below natural ground level. The distribution of soil pressure under a footing is a function of the type of soil, the relative rigidity of the soil and the footing, and the depth of foundation at level of contact between footing and soil.
Always make the footing at least twice as deep as the thickness of the wall and twice as wide (Fig. 2). For example, if you are using 8" blocks, the footing should be at least 8" deep and about 16" wide.
The footing, or first row of your retaining wall, should be about 4 to 6 inches deep and about 12 inches wide, or twice the width of the block you are using. The blocks should sit about halfway into the soil.
Rules of thumb commonly used by designers to establish the geometry of the wall include (refer to diagram): Base width = 1/2 to 1/3 of the height of the wall. Base thickness = 1/8 of the height of the wall but not less than 12 inches. Stem thickness = 6 inches + ¼ inch for each foot of wall height.
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).
A typical foundation wall minimum thickness of eight inches applies to walls eight feet or less with no more than seven feet of soil pressing against it. Foundation walls taller than eight feet with more than seven feet of soil pressing against it requires a larger foundation wall 10 to 12 inches in width.
Regardless of the type of masonry material you are using to build the wall, concrete is the material of choice for the footer. A typical footer is twice the width of a wall and equal in depth to the wall's width. The footer should rest on a 6" gravel base set below the frost line.
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 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.
Effective Depth locates the tension rebar in the panel, and is used to calculate "shear depth" for calculation of actual shear stresses. As with beams, the Effective Depth in a shear wall is measured from the compression edge of the wall to the centroid of the tension chord rebar.
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).
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.
Strip Wall Footings are constructed with typical slab depths between 6”-8” (15-20 cm), footing widths of 12”-24” (30-61 cm), and lengths that vary as needed. Strip Wall Footings are commonly paired with column widths of 6”, 8”, 10” (15, 20, 25 cm).
Retaining wall foundation depth should be 300mm if the soil is firm and well-drained, or 450mm if less firm and unstable.
For a 6-foot wall, the depth of the footings typically should be at least 1/3 to 1/2 the height of the wall. This means you would want the footings to be around 2 to 3 feet deep.
The minimum footing thickness is 6 inches. 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.
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.
You can look up the recommended footing size, based on the size and type of house and the bearing capacity of the soil. 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.
In reinforced and plain concrete footings, the thickness at the edge shall be not less than 150 mm for footings on soils.
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.
Depth of footing above bottom reinforcement shall not be less than 150 mm for footings on soil, nor less than 300 mm for footings on piles.
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.