How to use the waterproofing material calculator
Enter the floor width and length with the wall upstand height and the page adds the upstand worked out from the perimeter to give the total coated area. Add the rate per square foot from the product data sheet, the number of coats, a waste percent and the weight of one pail, and you get the material weight and the pail count. Reinforcement width and lap give the fabric length for the floor.
Areas are dimensions multiplied, and the material weight is area times rate times coats with waste added on top. The pail count is rounded up only once, at the end. The page is current as of October 2026, and working area out from sizes is a definition rather than a standard.
Coverage rates for particular products and a waste allowance were not confirmed in an authoritative source; makers differ, so no value is suggested and only your figures are used. Membrane thickness checks, substrate condition and system selection are not covered. This calculator is for reference and does not replace design. Review by a qualified engineer is required.
Frequently asked questions
Coverage rates per product were not confirmed in an authoritative source. Two membranes of the same family can differ between makers, so no rate is offered here and the page uses the figure printed on your data sheet.
The floor width and length give the perimeter, which is then multiplied by the upstand height. That assumes the upstand runs all the way round, so adjust the sizes or scale the result if only some walls are coated.
It assumes strips laid across the floor width and lapped by the amount you enter, so the floor length is divided by the effective width and multiplied by the width of each strip. Reinforcement at upstands and corner detailing is not covered.