This house is 60 feet long and 25 feet wide. The area of this house section is 1500 square feet. The area of the garage is 500 square feet.
The front porch is 40 feet long and 5 feet wide and has an area of 200 square feet. The total square footage in the house foundation is 2200
square feet. The 40 feet long and 5 feet wide and has an area of 200 square feet. The total square footage in the house foundation is 2200
square feet. The are for the main footings and grade beams. The next item to figure would be the linear footage of the main exterior footings.
In this particular house there would be 220 linear feet of main next item to figure would be the linear footage of the main exterior footings. In
this particular house there would be 220 linear feet of main footings. Depending on the type of foundation and which walls are load bearing,
there might be other footings called grade beams. These footings act like beams in the foundation to provide extra support for walls that might
carry the load of the ceiling. There is 153 linear feet of grade beams in this house. Once you have calculated these items, you now need to
look at the structural details and see what details there are for the main footings and grade beams.
Summary: When you break up the foundation as stated above, you will
end up with the following sections and dimensions:
A slab 4 inches thick over the whole area of the slab > 2200 Sq/Ft
Exterior footings that are one foot wide and one foot deep > 220 Ln/Ft
Grade beams that are one foot wide and 4 inches deep > 153 Ln/Ft
One cubic yard of concrete will cover eighty one square feet of area. If
you divide the area of the slab (2200 Sq/Ft) by 81 Sq/Ft (1 cubic Yard),
you get approximately 27 yards of concrete for the slab 4 inches thick.
Since the exterior footings are 1 foot wide and 1 foot deep, all you have
to do is divide the linear footage by 27 cubic feet ( 27 cubic feet in 27
linear feet of footings 1 foot wide and 1 foot deep). By doing this, you will
get approximately 8 yards of concrete in the exterior footings.
Now, if you add the totals you will have approximately the total concrete needed in the
Slab 4 inches thick > 27 Cu/Yds
Exterior Footings > 7 Cu/Yds
Grade Beams > 2 Cu/Yds
Total Concrete > 36 Cu/Yds
Depending on the job, you can add a waste factor of maybe 5% or more to make sure
you have enough concrete. In this case with 36 yards, you could order 4 nine yard loads
and save the last for a clean up load.
This a simple example of how to estimate the concrete in a foundation. The basics are
the same and if you break the foundation into sections it will make the estimating
easier. Below are the formulas that were used in this example.
Linear Feet is probably the simplest quantity to calculate.
Linear feet = number of items x the item length
Square Feet is a simple process of multiplying the length x the width.
Square Feet = Length x Width
Cubic Feet adds one other dimension to square feet. There are 27 cubic feet in a cubic
Cubic Feet = Length x Width x depth
Cubic Yard is used to determine how yards of concrete or fill dirt might be needed for
the job. There are 27 cubic feet in a cubic yard of fill dirt and concrete.
The grade beams worked out to be 1 foot wide and 4 inches deep. This works out to be the same as the slab thickness. There is 153 Ln/Ft
of grade beam which is one foot wide. This will equal 153 Sq/Ft of grade beam 4 inches thick. If you divide 153 Sq/Ft by 81 Sq/Ft you will
get approximately 2 yards of concrete.
Category Construction Glossary