Is there a formula that I might use to try to figure out how much material I need to put in a foundation for a building? It will be pier & beam, not a slab. I'm trying to calculate about how much it's going to cost so I can know how much I can expect to spend. Thanks for your help. det28

You have to figure out the amount of cubic feet of concrete required i.e. length X height X thickness. This will result in the amount of cubic feet required. Then divide the total by 27 (27 cubic feet in a cubic yard). Concrete is sold by the cubic yard. You can convert inch measurements to feet for these calculations by dividing by 12. For instance a wall 8" thick is 8/12=.67 ft.in thickness. I usually order a little more concrete than I calculate and set up a form somewhere to pour a little slab so I don't waste the leftovers. Concrete here has gotten to be very pricey.

I certainly appreicate the reply. We are looking at putting in a 40' x 40'. One side will have a porch all the way across. We've built small things (sheds, chicken houses, etc.) but nothing on a large scale. I'm wondering if the foundation might not be better accomplished by a professional. Our problem is the money part of course. We are planning on building a steel frame since my husband has some experience with that and we have a friend that is going to help us. The friend is building a steel frame house now. We are willing to do all the work ourselves, including the foundation, but I know that if the foundation is off, everything else will be too. Including being unsafe. Thanks again for the advise and any other that you might have to offer. det28

Our house including the porch measures 42 x 40 ft. We did a block perimeter on concrete footings and then concrete footings were dug and poured inside the perimeter for the block piers that are every 6 ft. On top of the piers we have three 2 x 10's sandwiched with 3/4 inch plywood and bolted. The seal plates are 2 x 8 pressure treated. The floor is engineered I-joists (9 1/2 inches) on 16 inch centers. The perimeter boards are 2 x 10's in order to save money vs the engineered ones. On top of that is 3/4 inch tongue and grove CDX that has the guarantee that it won't warp or disintegrade if it gets wet----very important if you are doing all this yourself and you live in an area where you gets lots of rain. Materials ran us about $6 sq ft (about $10K). Labor for digging the fotings and doing the concrete and laying the blocks ran another $2 sq ft ($3600) We live on mostly clay and rock and it takes a backhoe and someone who can do a good job of running it and we never laid block before and decided it was better to have it done. Materials have gone up substantially since we did this, so it would run about $11-$12 sq ft at least if we had to do it now.

Concrete has a 25% 'compaction factor', the open space between the gravel is filled by the sand, the open space between the grains of sand are filled by the fluids, ect. If your hand mixing add 25% more materials (in ratio) to the overall volume.