A Simple Tool That Protects Your Waterproofing System
Author: QXO | March 2, 2026
When applying waterproofing materials, installing within the manufacturer’s thickness recommendations is important. Various issues can arise if these coverage rates are not followed.
Moisture-cured urethanes can blister and bubble if applied too thick. Thicker than designed applications of vertical coatings can sag on a wall or fail to cure properly. When these same materials are applied too thin, they can result in early failure due to early wear or tear when exposed to movement.
The best method to follow recommended coverage rates is to use the grid system, which calculates how much material is required for a measured area. However, there is a simple tool that can be used to measure the wet-film thickness of a coating too. Wet-film thickness, or WFT, is the thickness of a coating as applied wet on a surface. Dry-film thickness, or DFT, is the thickness of the coating after it completely cures, and the liquid portion of the coating evaporates or is used up in the chemical process.
A Wet Film Thickness (WFT) gauge is a rectangular device that uses notches that are marked in mils - a mil is 1000th of an inch - and is placed at a 90-degree angle into the fresh wet coating. These gauges
can be used for both vertical and horizontal surfaces. The gauge is placed into the wet coating, and the teeth corresponding to each mil are observed. The last tooth that shows evidence of wet coating is the thickness in that particular area. Combined with the use of the grid method, using WFT gauges can help prevent issues related to coating thicknesses on a project.