Why a moisture vapor barrier matters (especially in Florida)
In waterfront South Florida, the #1 avoidable coating failure is moisture. On-grade slabs sit close to a high water table and push water vapor upward. If that vapor gets trapped under a coating, it forms blisters that lift the floor. A moisture vapor barrier stops it.
What causes moisture blisters
Concrete is porous, and vapor moves toward the surface. Under an impermeable coating, pressure builds in the slab's capillaries until it exceeds the bond strength — and the floor blisters and delaminates. This is called osmotic blistering.
How we test for it
We test every slab with ASTM F2170 (relative humidity probe) or F1869 (calcium chloride). Anything above roughly 75–85% RH needs mitigation — extremely common near the coast and on ground-floor slabs.
What a barrier does
A moisture vapor barrier is a 100%-solids epoxy applied first that blocks emissions on slabs up to about 99% RH. It's only added when the test calls for it — but when it's needed, it's the difference between a floor that lasts and one that fails in months.