A broom finish is a well-known technique for making concrete slip resistant. It’s created by running a broom over the surface of freshly troweled concrete to create a textured finish. As an Applicator Developer, I’m consistently asked if a broom finish is a sufficient slab profile for a resinous flooring system. The answer is always no.
A concrete sub floor should have a CSP of at least 3 for optimal bond of the flooring system; concrete with a broom finish has no related CSP number. In addition, the surface of a concrete slab is always the weakest part of the floor. Best practice is to grind off the broom finish and then shot-blast the floor.
Why the two-step process? Depending upon your equipment, and the degree of the broom finish, your blaster may have a tendency to drop/waste a significant amount of shot if you skip the integral grinding step.
So why not just grind? Although grinding will take off the broom finish and (depending on the PSI of the slab) may give you a possible CSP of 3-4, it will also create a very fine dust that is almost impossible to extract even with the best vacuum. Don’t take the chance. Following the grinding by shot blasting is an extra step and an added cost, but costs much less than that of a failed floor.
Always consider all of your surface prep options and obligations before you bid to ensure your costs are built in on the front-end. If you’re unsure, give the Technical Services Department a call and we’ll walk you through best practices to ensure you put down a floor that will stand the test of time.