have 80m2 of quickstep coming up on a concrete subfloor the building is quite old 1940s will i still need to put some sort of dpm sheeting done prior to the woodtex?
I have uplifted quite a few laminates in the last few years with a dpm sheet on the subfloor and it's been wet. It has trapped the moisture in. So depends on the water table of the house.
its a farmhouse with a slight slope leading down a hill its a bit of a grey area as i was told always to put a dpm sheeting whatever underlay you use
if the subfloor is above 75%RH it needs a dpm barrier. If below 75% RH then it needs a underlay with a built in Vaporous barrier only. most underlays for concrete have a vaporous barrier only, not a dpm.
on a concrete floor you need to use a vaporous barrier. DONT confuse a vaporous barrier with a DPM sheet. Underlays dont tend to have dpm sheets built in. A dpm grade is much thicker than a vapor barrier. Like i say, depending on RH of floor will determine if you need a vaporous underlay or DPM underlay. (dont forget most underlays are vapor only) As a example, timbermate XL says it has built in moister barrier. If you read the small print it can only be used on subfloors below 75% rh. So would require a additional DPM layer on a wet concrete subfloor. (above 75%RH)
Also if built on marshland, you need a radon barrier Dpm sheet to prevent dangerous gases leaking into the house methane etc...
