Hi all, I have a bungalow with concrete subfloors. They've recently been primed and leveled using latex screed. There is no DPM in the floor, the house was built in the early 60s. Previous tests before self leveling showed humidity levels higher than ideal. My question is: for a Laminate floor, would an underlay system with built-in moisture barrier be sufficient to address the issue of rising moisture? I gather that these barriers still allow moisture through, but slow the rate down. Is this correct? So I don't need to worry about moisture building up underneath the underlay, or making its way to the sides and up the walls instead? For some reason, my floor levels are a bit above the DPC and there is typically a small gap between the sub base and wall around the edges where a skirting board would be located - I add this in case it is of any use! Would be grateful for advice. Many thanks
Thanks for the response, tarkett. Could you give me some examples of the form a surface level DPM would take - is it like a paint? - and what the cost would be for, say, 10sqm? All the advice I've had to date has been that a vapour barrier would do for laminate. I was told that laminate and carpet are less onerous, but glued down flooring you have to be more careful about reducing moisture. Also, is the DPM you refer to a 100% barrier, or does it still let some moisture through? My concern is about the moisture being forced out to the sides and then causing mold up the walls.
It slows down the release of moisture drastically so you don’t have issues with your flooring, carpet and laminate should still be installed on concrete subfloor with a mechanical dpm and a Rh% of 75 or below. I can’t say exactly what prep you’ll need without proper testing but a screed dpm sandwich of Ardex NA, DPM 1 C, Ardex NA should do the job if the concrete is sound and not degrading, price wise you would need to get a professional in to price up. Sent from my iPhone using Tapatalk
With a hygrometer test reading below 90 you could use a underlay with a built in dpm. Or a isolator sheet or a Triton dpm sheet. Think even timbermate goes up to 90% rh. Or put in a surface dpm. surface dpms do push moisture into the walls. You can’t use them in very old buildings that can’t take moisture.
Hi Berty Jason Darger here with Utah Flooring & Design. An underlayment system with a built-in moisture barrier can help to slow the rate of moisture migration through the concrete subfloor, but it is not a guarantee that all moisture will be stopped. These underlayments typically have a polyethylene or similar type of moisture barrier film on the underside which will help to slow the passage of moisture, but may not stop it entirely. However, its important to note that installing a DPM(damp proof membrane) in the concrete subfloor is standard practice for new builds and renovation projects, therefore lack of DPM in your current condition is quite an issue. It is not an ideal situation, lack of DPM may lead to a future problem with moisture. The house built in early 60s and with no DPM could have been cause for moisture to already be present. The high humidity level also supports this fact. Since the humidity level is high, I would suggest you to consider addressing the moisture issue before installing new flooring. A professional can do a moisture test to confirm the extent of the issue, then suggest appropriate remedies to reduce the level of moisture in the subfloor, such as ventilation and dehumidifiers. Once the moisture level is under control, you can then proceed with installing your laminate flooring and the underlayment system with built-in moisture barrier. Regards, Jason Darger
