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Concrete Coatings in North Florida: Why You Need A Moisture Barrier When Having Epoxy Concrete Floor Coatings Installed

A moisture barrier is a crucial step when applying epoxy coatings in hot and humid Northeast Florida, especially over concrete substrates. Its main purpose is to prevent moisture vapor transmission (MVT) from the concrete slab, which can cause delamination of the epoxy coating, bubbling or blistering, poor adhesion and coating failure.
 
Why Moisture Barriers Are Needed

Concrete is porous and often contains moisture, especially:
 
  • In new slabs (curing can take months)
  • In areas with high ground water
  • On-grade or below-grade slabs without a vapor barrier underneath


If not properly addressed, this moisture can migrate up through the slab and disrupt the epoxy coating.
 
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Testing for Moisture

Before applying an epoxy coating, test the moisture condition using:
 
  • Calcium Chloride Test (ASTM F1869) – Measures MVT rate (lbs/1000 ft²/24 hr)
  • Relative Humidity Test (ASTM F2170) – Measures RH within the concrete slab

Epoxy coatings typically require MVT < 3 lbs/1000 ft²/24 hr or RH < 75%. If your readings are above this, you’ll need a moisture mitigation product.


Moisture vapor transmission (MVT) can cause:
 
  • Delamination of the epoxy coating
  • Blistering or bubbling
  • Adhesion failure over time
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Best Practices

Always test for moisture before coating.
 
  • Use a compatible moisture barrier primer if high MVT is detected
  • Follow manufacturer’s instructions on prep, thickness, and cure time
  • Ensure the substrate is clean, roughened, and dry before applying the epoxy or barrier


For garage slab epoxy coatings, using a moisture barrier is essential if there’s a risk of moisture vapor rising through the concrete, even if the slab looks dry. This is common in many garages, especially those built on-grade or without an underslab vapor barrier.


Garage floors are often exposed to:
 
  • Ground moisture (especially in older homes)
  • Condensation cycles from temperature shifts
  • Salt and chemical exposure, which can worsen slab condition

Contact Us!

At Gorilla Coatings, our services always include moisture barrier testing and protection. Contact us to learn more!
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