Concrete can look dry yet hold moisture inside. Under a coating this moisture creates vapour pressure; work started without testing may later blister.
Looks can deceive
A newly poured slab or one resting on the ground can hold moisture inside even when its surface looks dry. Over time this moisture moves towards the surface.
What moisture does to a coating
A sealed coating traps moisture; vapour pressure underneath can weaken adhesion and show up as blisters, lifting or whitening.
How it is measured
Surface moisture meters give a quick indication. For more reliable results, methods that measure inside the concrete or a simple sealed plastic sheet test on the surface can be used. Several points should be tested.
If moisture is high
Options are to wait for the slab to dry, or to use moisture-tolerant primers or moisture barrier systems. The choice depends on the results and the schedule.
Ground-bearing slabs
Slabs without a damp-proof membrane can receive continuous moisture from the ground, which makes system choice even more important.
Frequently Asked Questions
How long must concrete dry?
It depends on thickness, weather and ventilation; decide by measurement, not estimate.
What if coating is applied without testing?
If moisture is high, pressure builds under the coating and blistering or lifting can follow.
Can damp concrete never be coated?
It can, under suitable conditions, with moisture-tolerant primers or barrier systems.
Would you like a site survey for your floor? HBK Epoxy Flooring, based in Gaziantep, offers free surveys and quotations in the surrounding provinces.
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