Materials, Measurement & Volume
So how does one calculate the material needs for a project?
I’ve often wonderd about how people calculate material needs. You usually don’t want to pay for more than you need, and you sure don’t want to run short of material in the middle of a job!
Let’s say we want to order enough sand to fill a sand box.
The dimensions are:
length = 4′
width = 4′
We need to find the volume and convert it into cubic yards because that’s the measurement the delivery companies use.
length * width * height = volume
So in this case we will take 1 * 4 * 4 = 16 cubic feet
Divide cubic feet by 27 ( the number of cubic feet in a cubic yard )
16 divided by 27 = .5925 cubic yards will be needed
Approximately .60 cubic yards will be needed to fill the sand box. Seems like one might be able to pick up that amount at a home center. Not too much need for delivery.
Let’s say you will be building a cob wall.
What ingredients will we need?
Cob is ideally made of course angular sand and clay rich soil.
The ideal ratio will be 70% sand and 30% clay ( give or take depending on soil content).
If the wall dimensions are :
length = 35 ‘
width = 1.5 ‘
height = 8 ‘
35 * 1.5 * 8 = 420 cubic feet
420 cubic feet.
That would be approximately 420 5-gallon buckets or 140 wheel barrels of material!
divide cubic feet by 27 ( the number of cubic feet in a cubic yard )
That gives us a total of 15 cubic yards, of which 70% will be sand and 30% will be clay:
15 * .7 = 11 yards of sand
15 * .3 = 5 yards of clay
Of course, it would be better to add a little to your order, just in case. Better to have too much than not enough! The delivery is usually the most expensive part of getting sand or clay. If you have ideas for future projects – fill the truck full, since they’ll charge you the same amount for delivering 1 ton as 12 tons. Watch out! Some companies want to charge you for delivering from Timbuktu to your site, where others will be more fair on mileage.
We haven’t even talked about ordering straw yet, but we’ll leave that for another article.