• by Taylor

Florida’s high water table and year-round humidity create a silent threat to epoxy floors: vapor pressure. Water migrating up through the slab carries salts and air that break the bond between concrete and coating, causing blisters, bubbles, and complete delamination. Installing a moisture-vapor-barrier (MVB) epoxy primer—and testing relative humidity (RH) before you coat—turns that weakness into long-term strength.

Why Vapor Pressure Matters in the Sunshine State

• Average groundwater sits just feet below grade along Tampa Bay.
• Afternoon storms saturate soil and boost slab moisture overnight.
• Porous concrete acts like a sponge; moisture rises and pushes on any film-forming coating.

Without a vapor-retarding primer, even a premium flake or metallic system can fail within months.

Step 1 — Reliable RH Testing

Concrete moisture isn’t guesswork; it’s measured with in-slab RH probes. Florida contractors follow ASTM F2170:

RH Reading	Risk Level	Recommended Action
≤ 75 % RH	Low	Standard epoxy primer is acceptable.
76–85 % RH	Moderate	Apply one coat of 100 %-solids MVB.
86–99 % RH	High	Two heavy coats of MVB or switch to vapor-open system.

A reputable installer shares RH data in your written quote, proving the slab is suitable—or specifying the barrier needed.

Step 2 — Installing the Moisture-Vapor Barrier

1. Diamond-grind to ICRI CSP-2/3 for maximum mechanical profile.
2. Vacuum with HEPA filtration to remove dust that blocks adhesion.
3. Roll or squeegee a 100 %-solids moisture-vapor-barrier epoxy at 12–15 mils.
4. Back-roll to eliminate pinholes; cure 2–4 hours.
5. Proceed with build coat, flake or metallic layer, and UV-stable polyaspartic clear.

These barrier resins tolerate up to 25 lbs/1,000 ft²/24 h of moisture vapor emission—far above typical Gulf-coast slabs.

Benefits of a Proper MVB Primer

• Stops water-borne salts from blistering the coating.
• Prevents alkaline efflorescence that clouds clear coats.
• Extends floor lifespan from 3–5 years to 10–15 years or more.
• Qualifies the project for lifetime adhesion warranties.

Warning Signs Your Existing Floor Lacks Vapor Protection

• Random yellow or white blisters that grow after storms.
• Damp spots or “sweating” concrete under the coating.
• Peeling beginning at control joints or edges where vapor escapes first.

If you see these issues, a full grind-off and MVB re-prime is the only permanent fix.

Costs and Timeframe in Tampa Bay

Size	Added Cost for MVB*	Extra Time
Single-car garage (200 ft²)	$250–$350	+½ day
Two-car garage (400 ft²)	$400–$600	+½ day
1,000 ft² warehouse bay	$1.10–$1.50/ft²	+1 day

*Includes material and labor. Far less than the cost of grinding off a failed floor later.

Takeaway for Florida Homeowners

Skipping RH testing or a moisture-vapor barrier is gambling with your investment. A 30-minute probe test and one extra primer coat ensure your epoxy floor stays bonded and beautiful despite Tampa’s humidity.

PalmGuard Epoxy moisture-tests every slab and installs high-build MVB primers where needed—backed by a written lifetime adhesion guarantee.