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cubic foot calculations

1K views 5 replies 4 participants last post by  doingpavers 
#1 ·
I'm more of a 2 dimensional kinda guy so I was hoping some one could check this out.

I am going to build end walls for my culvert (before I do the drive way)

each wall will have a footer 11ft long 2 feet wide and 16" high.

on each footer is a wall with an angled back so the bottom of the wall is 16" wide and the top of the wall it 10" wide. the height of the wall (without the footer) is 40" and it is also 11 feet long.


I get 36 cubic feet for the footer which I think is 1.3 cubic yards

but I do not know how to go about doing the wall. I don't need exact. just close.
 
#3 ·
Since you are building two identical walls and footers the simplest method, avoiding having to figure the volume of the triangle involved, is to figure the two angled walls as a single volume.

Since they both have the same angle and dimensions you simply invert one wall against the other and add them together. In your case the walls are 16" wide at the bottom and 10" wide at the top. By inverting one wall the combined width would be 26". The height being 40" you now have a cross section area of 1040 square inches.

This 1040 times (11' X 12") or 132 gives a total of 137,280 cubic inches in the two walls or 68,640 cubic inches per wall. Since there are 1,728 cubic inches in one cubic foot this means your walls will each require 39.72 cubic feet of cement. There are 27 cubic feet in one cubic yard. 39.72 divided by 27 gives 1.47 cubic yards per wall.

The footers 132" X 24" X 16" will each require 50,688 cubic inches of cement. Divided by 1728 this gives 29.3 cubic feet of nearly 1.1 cubic yards each.

Total cubic yards needed will be (1.47 + 1.2) X 2 or 5.14 cubic yards of mud.

You'll no doubt have some spillage so order accordingly.

Double check my figures as I'm not as sharp as I once was.

Mike
 
#5 ·
I come up with 29.36 cubic feet in the footer....

11' x 2' x 16 inches (or 1.33 feet) = 29.26 cubic feet... not the 36 u stated... this comes up to 1.08 yards..
 
#6 ·
Yes. I botched that one up. I had 33 on a piece of paper, which is still wrong, because I used 1.5 feet. and then typed it out wrong here and put down 36.

I'm gonna have to tripple check everything i do. This would explain why the last bathroom vanity I made was an inch to deep. no math skills here.
 
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