Moisture Issues In Concrete Floors

oisture issues in concrete floors are one of the main reasons why epoxy flooring fails. Moisture occurs in newly poured concrete or when there are high moisture levels underneath the concrete slab due to poor drainage, naturally damp land, or a pipe leak.

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Areas such as Victoria, Tasmania, and Queensland, where there are higher levels of rainfall, tend to get more moisture issues than drier areas such as Western Australia and the Northern Territories.

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As concrete is porous, it is important to know how much moisture your slab transmits before you decide to apply epoxy or paint. Epoxy does not breathe, so any moisture trapped between the concrete and the epoxy can potentially delaminate or peel it when trying to evaporate.

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What are the signs of moisture issues?

Your concrete might already show signs of moisture issues without you realizing it. If you have areas on your garage floor with fine white powdery residue that comes back after cleaning, chances are there is efflorescence. Efflorescence happens when moisture travels through the concrete, condenses, and evaporates, leaving a residue of white powdery calcium.

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Another sign of moisture issues is if your floor and garage always feel damp. Due to climate, this can be caused by poor water drainage underneath the slab, leaky pipe, or naturally wet soil. Concrete might seem hard and dense, but it is porous, acting like a sponge when water surrounds it.

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If your concrete has dark spots that feel damp to the touch, it is likely absorbing water from underneath.

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How do you test for moisture in your concrete?

When doubting moisture issues, the simple thing to do is to perform a moisture test.

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This consists of an A4 plastic sheet and some tape. Place the plastic sheet on the concrete floor and tape all four sides to the floor. Let the sheet stay on the floor for 24 hours. Then peel it off and look for signs of condensation underneath the plastic sheet or dark spots on the floor. If there is condensation or dark spots, then it's highly likely you have moisture issues.

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If you do and are curious about how much moisture your concrete emits, you can use a humidity measuring device or do a simple calcium chloride test to find the exact amount of moisture.

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If your moisture levels are below 1.3kg per 90 m2 on average, you can apply most coatings on top of your garage. If they are above these, you must consider applying a moisture-blocking sealer or epoxy primer.

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One important thing to consider is that moisture tests are only indicative when performing them. If you do the test during the dry period of the year, you might not have any moisture issues, compared to if you do the test during a rainy period.

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The same applies whether your concrete slab is above grade or below grade. Slabs below ground level experience more moisture issues than slabs above ground level.

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Conclusion

The important thing to remember is that if you suspect your garage is experiencing moisture, it is best to perform a moisture test before applying any coating. This will save you a lot of time and money in the long run.