Because we were laying Karndean Flooring to a new extension we needed to check the % RH(relative humidity) of the concrete with a hygrometer.This told us that the concrete still had some moisture residue left from the initial mix and it was evaporating from the slab.This is normal because there is always a DPM under the slab and the moisture has only one way to go.Upwards.It usually takes 6 months,or 1 month for every inch of slab thickness to dry out completely.This is fine when laying carpet etc, because we're not talking tidal waves of moisture.However if you're laying a wood floor or a vinyl floor such as Karndean or Amtico or even Polyflor sheet vinyl then all that happens is the residual moisture rises to the surface,tries to evaporate but can't and just sits there.If it's under vinyl tiles or vinyl sheet then it just emulsifies the adhesive causing the floor to lift.If it's under wood it causes expansion and buckling of the wood, again causing the floor to fail.The DPM simply stops the moisture from rising through the floor and pushes it to the side of the concrete subfloor where it evaporates harmlessly,causing no damage to the finished floor.
10 окт 2013
