Floating floor over old mastic?

Question

I recently had carpet and asbestos tile tested and removed from my basement, and now am left with concrete covered with black mastic (non-asbestos per testing). I would like to cover the floor with floating planks, and was wondering if the mastic must be removed first.

The concrete is reasonably level with some pitting, and does not appear to be sealed. There is an "All-dry" water mitigation system in place around the edge of the concrete directing any moisture towards the outside of the foundation, so the concrete is unlikely to see much moisture.

My understanding is that floating planks over concrete is usually 3 layers:

1. 6 mil vapor barrier
2. Underlayment
3. Floating planks

Provided the concrete does not need leveling, will I have problems if I install these layers directly without removing the mastic?

Answer 1

As with any flooring the flatter and smother the base is the better the end result will be. I have had good luck with a heat gun and a putty knife. You do really want to remove the high spots for a good looking floor that will last.