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Epoxy moisture control systems can be applied over concrete with relative humidity levels up to 100%, and there are systems available on the market today that can be applied over concrete that is physically damp. In some cases, with the use of an epoxy moisture control system, floor coverings can be installed just 7 days after the slab is poured.
A common example is polyethylene sheeting laid under a concrete slab to prevent the concrete from gaining moisture through capillary action. [5] A DPM may be used for the DPC. Integral damp proofing in concrete involves adding materials to the concrete mix to make the concrete itself impermeable. [4]
Masonry walls are built with a damp-proof course to prevent rising damp, and the concrete in foundations needs to be damp-proofed or waterproofed with a liquid coating, basement waterproofing membrane (even under the concrete slab floor where polyethylene sheeting is commonly used), or an additive to the concrete.
Uncovered concrete dries from the top down. Concrete moisture meters measure only the top inch at most [5] and this area is drier than the concrete further down. Once a floor covering has been installed the moisture in the slab equilibrates. In order to ensure the equilibrated moisture will be a safe level [6] for a floor covering, a relative ...
In many cases, damp is caused by "bridging" of a damp-proof course that is otherwise working effectively. For example, a flower bed next to an affected wall might result in soil being piled up against the wall above the level of the DPC. In this example, moisture from the ground would be able to ingress through the wall from the soil.
In poured concrete foundations, cracks and pipe penetrations are the most common entry points for seepage. These openings can be sealed from the interior. Epoxies , which are strong adhesives, or urethanes can be pressure injected into the openings, thus penetrating the foundation through to the exterior and cutting off the path of the seepage.
Concrete sealers are applied to concrete to protect it from surface damage, corrosion, and staining. They either block the pores in the concrete to reduce absorption of water and salts or form an impermeable layer which prevents such materials from passing.
An MVTR result without specifying these conditions is almost meaningless. Certainly no two results should be compared unless the conditions are known. For example, the effect of temperature on the permeability can be as high as 10% per °C, making it possible that MVTR results achieved at 23°C and 37°C can differ by a factor 4.