When I talk to mudjackers who want to get into foam lifting, they almost always want to know the difference in estimating how much material is needed. In fact, anyone new to slab lifting with polyurethane foam will ask how to estimate material, not just people experienced in mudjacking. If you use a cementitious slurry, you are probably used to calculating in cubic yards, but with foam, you need to figure out how many gallons you might need.
Here’s the way to figure it out.
There are two parts to slab lifting: 1- filling existing voids and 2- lifting the slab.
For void filling: Find out the free rise expansion rate of the material. This should be on the technical data sheet for the product. There are 7.48 gallons of liquid in a cubic foot, so divide that by the expansion rate to get material in a cubic foot. For example, if you are using our Revolution compact slab lifting system with Precision Lift 2135, it has a 20 times or 20x expansion rate, so:
7.48 ÷ 20 = .374 gallons per cubic foot
There are 27 cubic feet in a cubic yard, so in this example, there are approximately 10 gallons per cubic yard.
For slab lifting: Because the foam is confined when lifting a slab, the expansion rate will be affected. What we have observed in our many years of experience is that usually a half a pound of polyurethane will lift one square foot ½”. That’s less than ½ a pint of material. (There are roughly 10 lbs. to a gallon of polyurethane resin.) This is pretty typical for lifting foams on the market.
We provide free slab lifting estimating calculators on our website for both gallons and pounds. If you’ve got questions, call your rep or our main number at 800-321-7212.
By David Dingler, product development and technical services manager