Acceptable Moisture Levels In Concrete Floors

Moisture meters can only check the moisture near the surface of a concrete slab which is not sufficient for predicting how the slab will react to having sealant applied or other building materials installed over it.

Acceptable moisture levels in concrete floors.

The barrier membrane shall be installed continuously under the slab and over a minimum 100 to. For flooring or related materials as an example the relative humidity must usually be below 80 and the floor under the plastic should be free of dampness discoloration or damp odors. With a typical concrete floor about a quarter to a third of the original water content will evaporate which could be 6 to 9 l m 2 for a 150 thick slab. Determining what humidity level is acceptable depends upon the surface treatment to be applied.

Rh instruments can be independently calibrated directly traceable to national standards. Concrete slabs often have thicknesses measured in feet not inches. Take the readings in at least 20 spots per 1 000 square feet of flooring and average the results. Ed wagner answers the questions visit http www rhspec.

1 to prevent moisture migration up through concrete substrates located on and below grade and damage to installed floor coverings the concrete slab shall be protected from ground moisture and hydrostatic pressure by the use of an industry approved vapour retarder moisture barrier or waterproof membrane having a permeance of less than 0 3 perms 0 2 metric perms in accordance with astm e 96. How moisture gets into concrete. Rh for floor moisture measurement is not new it was first used to measure moisture in concrete floors as part of pca applied research programs in our laboratories beginning in the 1950s. Some flooring system manufacturers have products that can handle 95 rh or mor 2.

Most concrete moisture meters only check surface moisture. Acceptable moisture levels in concrete according to astm standard when testing via astm f2170 the rh level of a concrete slab needs to be at or below 75 unless the flooring system manufacturer provides alternate guidelines. In general 12 moisture or above is too wet to install flooring.