Calculating the Amount of Concrete Needed For Footings.
Footings will rarely follow the drawing exactly.
In rocky soil the footings may collapse when big rocks are excavated
This was supposed to be a 12"*12" footing, but note how the left
side of the footing has collapsed. Calculate the true width.
The excavator may have dug too deep, or it may have rained and footings
needed to be dug out deeper to reach firm soil. So it is important to check a variety of
spots on your footing and get an average size. Then use the calculator to figure the
amount of concrete needed.
House slabs on grade that are 8" out of grade with a 4" slab
also have some of the footing above the grade too.
This 12" x 12" footing needs to be calculated
12" x 16" so the footing is figured to go above grade to reach the 4" slab
thickness.
