Concrete Footing Loads must be Distrubuted to Undisturbed , Compacted Soil
Concrete footing loads, width and depth can differ depending on a number of facts.
section thru concrete footing
Learn more about the design of a Concrete Footing Building Codes
Concrete Footing must Distrubuted loads for the above structure (live and dead load) to Undisturbed Soil, Compacted soil and rock with bearing capacity that exceed 75 kPa.
Concrete footing for a residential house is referred to as a wall footing or a strip footing.
Some footing are even reinforced with steel rebar to spread load across an area of soil more efficiently without failing.
Concrete footing must be placed on undisturbed soil to reduce the occurance of rapid setttlement.
Hand tools are used to dig the final foot of dirt for the formwork to be constructed.
Concrete Footing Design Rule of Thumb
As a general rule of thumb the thickness of the concrete footing must not be less than the larger dimension of 100mm (4") or the width of the projected concrete footing beyond the exterior face of the foundation wall.
Concrete footing widths are important because there ensure that the concentrated load applied by the structure above is distrubuted over a wide enough area to avoid failure of the footing and or rapid settlement which can damage the wood frame structure.
This settlement is normal and should happen gradually over a period of 5-10 years, but if the concrete footing loads are not being distributed evenly over a surface cracks in the wall corners and above openings, sloping floor, and sticking doors and warped openings are all results of rapid settelment of the foundation walls
Other cause of settlement are due to:
Poor soil compaction
Soil shrinks due to loss of moisture content
Soil swelling due to increase presences of water
Water table level changes
Importance of Basement Underpinning.
Underpinning basement can be costly but necessary for a lot of reasons that involves improving distribution of concrete footing loads.
Construction of adjacent building disturbs basement foundation
Existing foundation wall has settle excessively create structural problems
Increase the height of the basement for comfort
Separate basement entry
Underpining benefits come from the new, enlargened basement/living space which can safely carry the load of the structure above.
Retaining walls also have footing design especially to serve the purpose of the retaining wall which is to retain soil.
Retaining wall retains or resist the pressure of the earth on the other side. This type of wall
can be precast and brought to the site
can be erected with pressure treated wood on the site or
can be sitecast with poured concrete.
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