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Epoxy floor coating over acid stained floor with efflorescence

by Robin
(Sammamish, WA)

Acid Stained floor with efflorescence deposits

Q. I have a decrorative concrete floor in my carriage house where I store several high-end cars. The floor is saw-cut in a design and then acid stained. Unfortunately, I live in the Seattle area and the guy who poured it didn't use a moisture barrier and the appearance of the floor is now being marred by efflorenscence deposits coming up through the concrete. I'm wondering if I could coat over the (two color) design with two colors of epoxy floor coating, thereby keeping the design, restoring my floor to a clean, beautiful look, and adding durability to it. Will the presence of the deposits in any way affect the application, durability or ongoing appearance of the epoxy coating? Will the fact that these deposits will continue to leach up through the concrete even after I apply the epoxy affect it in any way, or will the the coatings keep the deposits hidden beneath them forever?

If this won't work, I fear my only real alternative is to tile over the floor, unless you have any other suggestions.

Thank you for any help you can offer.

A. You shouldn't apply epoxy. Epoxies and urethanes don't do well with hydrostatic pressure. They are non-breathable coatings and will bubble. Eventually the problem will probably go away as the salts get used up. I can't say how long because there are too many variables. You could try stripping the sealer and then applying a penetrating sealer or densifier. These types of sealers will react with the free lime to create a gel that hardens and fills the pores of the concrete, thus creating a barrier. Then seal it with solvent based sealer to restore the appearance. I've never done this but it is worth a shot before covering it with tile or an overlay.