The thickness of a concrete retaining wall depends on the height and soil conditions, but typically ranges from 8 to 12 inches.
In reinforced and plain concrete footings, the thickness at the edge shall be not less than 150 mm for footings on soils.
Use crushed gravel with stones sized between 1/2 and 3/4 inch. The crushed fines from the gravel is what will allow you to compact it to a solid base. Your base depth should be 1 inch per 1 foot of wall height but no thinner then 4 inches thick. The base width should be twice and wide and the wall width.
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.
"Usually a first guess size for a cantilever retaining wall footing is about 40-60% of the wall height." For a standard cantilever retaining wall, that usually works, but for a toe wall, without a heel for the weight of the backfill soil to resist overturning, the footing may need to be much larger.
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).
In summary, retaining walls do need a footing to ensure they are structurally sound and have proper drainage to prevent cracking or collapse. Without a footing, the ground beneath the retaining wall can shift, which can cause the wall to shift as well, leading to cracking or collapse.
Footing thickness - 8 to 12 inches.
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.
For the Preliminary analysis, thickness of the base slab can be taken H/10 to H/15. H is the total ht of the retaining wall. Min thickness not less than 300 mm. Thickness assumed should be checked from bending moment and shear force requirement.
Absolutely! Even a 2-foot retaining wall needs an effective drainage system. Without it, water can build up behind the wall, leading to pressure that might cause the wall to lean or even collapse. All walls need systems to manage water effectively, preventing damage over time.
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.
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.
The size of the wall will largely determine the size of the footing. For concrete, a poured concrete footing is the best. Block or brick walls should be a minimum of twice as wide as the planned wall. The footing of your retaining wall should be as thick as the wall's planned width.
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). What factors impact the strength of a building foundation?
They are made not less than 1 1/2 times the projection of the slab beyond the face of the pier or column or the edge of the baseplate of a steel column. It should in no case be less than 150mm 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.
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.
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.
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.
Dig a trench for the bottom row of blocks. They should be buried about 1 inch deep for every 8 inches of wall height. This provides strength and stability to your retaining wall. Make sure that your trench is level and compacted.
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.