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#1
05-24-2006, 11:49 AM
 azbikermom Guest Posts: n/a

We are going to be building a new home and are in process of getting our figures together for our construction loan. We would like to get bids on building the house pad but everytime I talk to someone they want to know how many tons of dirt I need but nobody is ever able to convert the figures to tons. We need a house pad that is 7000 sq. ft. and we need it built up about 30 inches. I understand that with the compaction rate we will need to add about 1/3 more onto the total amount of dirt needed. Can any of you math wizards out there help? Thanks!
#2
05-25-2006, 06:37 AM
 Robert Fogt Administrator Join Date: Dec 2005 Location: Seattle, WA Posts: 3,452 Rep Power: 13

First convert everything to the same base unit.

30 inches / 12 = 2.5 feet

Now calculate the volume needed.

7000 square feet * 2.5 feet = 17500 cubic feet

So thats how much dirt you need. The trouble is that not all dirt weighs the same, so the next part would just be an approximation.

Earth, loam, dry, excavated - 78 pounds/cubic foot
Earth, moist, excavated - 90 pounds/cubic foot
Earth, wet, excavated - 100 pounds/cubic foot
Earth, dense - 125 pounds/cubic foot
and the list goes on.....

I will use the dry earth as the example.

17500 cubic feet * 78 pounds/cubic foot = 1365000 pounds

Now to tons.

1365000 pounds / 2000 = 682.5 tons
#3
06-11-2006, 08:19 AM
 Blake Naranjo Guest Posts: n/a

I am in a similar predicament as the previous post. I am building a house pad that is 2100 Sq ft. My issue is that there is a 4ft difference from east to west that I will have to level. Using your caluclations (again using dry earth as the example) I came up with 327.6 tons of earth required. Is that right?
2100 x 4ft = 8400 cb feet
8400 x 78 - 655200
655200 / 2000 = 327.6

#4
06-11-2006, 11:11 PM
 Robert Fogt Administrator Join Date: Dec 2005 Location: Seattle, WA Posts: 3,452 Rep Power: 13

That would be correct for 4 foot of earth over 2100 square feet.

Though it sounds like in your situation you have 4 foot on one side and less on the other. Similar to a trapezoid shape like this one (but laying on its side).

Lets say you had to fill 2100 square feet from 4 feet deep on one side down to 1 foot deep on the other side. In that case you would need about 5290 cubic feet of earth, as compared to 8400 cubic feet if it was 4 foot deep over the entire area.

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