Why We Test Your Slab Before We Quote It

There is one measurement that changes a coating job on this coast more than any other, and most quotes never mention it. It is how much moisture your slab is pushing upward, and it is the difference between a floor that lasts and a callback.

What is actually happening

A slab on grade sits directly on soil. Water in that soil does not stay in the soil. It moves up through the concrete as vapor, continuously, and it varies by season. In February a slab can read comfortably dry. The same slab in August, after a month of afternoon storms, can be pushing several times as much. A coating installed against that pressure without accounting for it can lose its bond from underneath, which looks like peeling from the top.

The two numbers

Moisture vapor transmission is measured in pounds per thousand square feet per twenty four hours, under ASTM F1869. Slab relative humidity is measured as a percentage with in situ probes, under ASTM F2170. Both matter, and coating systems publish limits for both.

Why it decides the system

Our three basecoats have genuinely different tolerances. Two of them cap out around three pounds and 75 percent slab relative humidity. The epoxy basecoat, applied at sixteen mils, handles up to about twelve pounds and 85 percent. That is roughly four times the tolerance, and it is the single best reason to put an epoxy basecoat on a Florida slab on grade.

If the readings come back above even that, the answer is a moisture vapor barrier primer underneath the system rather than hoping. That adds cost, and we would rather tell you about it in the estimate than discover it later.

Why seasonal variation matters

Because a reading is a snapshot. A slab tested in the dry season can pass and still exceed the limit four months later. That is why the fix for a marginal reading is a more tolerant system rather than a note in a file, and why we lean toward the higher tolerance basecoat when a floor is on grade and the numbers are anywhere close.

What this means for your quote

We look at your concrete before we write a number. If a company quotes your floor sight unseen, they are either building a large contingency into the price or planning to find out the hard way. Every estimate we write is free and in writing, and the system we spec is a decision about your slab, not your budget, because all three cost the same.

Related: how our three systems compare, recent work, and how to reach us.