ᐅ Is a Damp Proof Membrane Required Under Floating Cork Flooring?

Hello,
we are having floating cork flooring installed. It is a new build, and the screed has passed the CM measurement test, so it is dry enough for installation. The floor installer is not using a PE foil as a vapor barrier, contrary to the manufacturer’s instructions. We find this a bit odd, since the installation guide clearly states that a vapor barrier is always required on mineral substrates like screeds.
The installer argues that this is not necessary for new builds, but rather for older buildings and those without basements, even though new screeds generally still contain more residual moisture.

How critical do you think this is, and should one insist on strictly following the installation instructions?

Hausbaer schrieb:

How critical do you consider this, and should one insist on strictly following the installation instructions?

Is the screed dry or not? What is the purpose of the vapor barrier then? If it is not dry, you must not install any flooring.

Hausbaer schrieb:

New buildings often have higher residual moisture in the screed.

So, does this mean you cannot install floors in new buildings because everything underneath would mold? That’s what the CM measurement is for. Then you know whether it’s ready for installation or not.

Then ask him if he assumes liability when working against the installation instructions. VOB DIN 18365 "Flooring Works"

nordanney schrieb:

Is the screed dry or not? What is the purpose of the vapor barrier then? If it’s not dry, you shouldn’t install any flooring at all.

So, does that mean you can’t install floors in new buildings because everything underneath would mold? That’s what the CM measurement is for. Then you know whether it’s ready for installation or not.

The floor should be dry, but in my understanding, screed always retains residual moisture for a long time. Whether this is truly relevant is what I’m trying to clarify here in the forum. Quote from the installation instructions:
"Vapor barrier: For all mineral subfloors, such as screeds or stone tiles, a vapor barrier is required. This also applies to concrete floors with integrated moisture barriers or underfloor heating, as well as concrete intermediate ceilings. There must be no partial cold or warm areas, as this can cause stress. Use a plastic sheet (PE film) with a thickness of at least 0.2 mm (0.008 inches), overlapping and sealing the sheets by at least 20 cm (8 inches). Lay the sheet so that it extends at least 5 cm (2 inches) up the walls."

T_im_Norden schrieb:

Then ask him if he takes responsibility for adhesion when working against the installation instructions.
VOB DIN 18365 “Floor covering works”

Yes, he does take responsibility. And yes, I am familiar with the DIN as well and am considering insisting on compliance with the VOB/C as contractually agreed. But I don’t want to make a big deal out of it. That’s why I’m asking here in the forum whether this vapor barrier is already strongly recommended. Quote from DIN 18365:

"3.5 Floating installation of laminate elements
Laminate elements must be installed floating; they are to be glued at the tongue on the long and short sides if they do not have a mechanical locking system. The subfloor, except for wooden substructures, must be covered loosely with a PE foil with a thickness of at least 0.2 mm (0.008 inches) and overlapped."

Hausbaer schrieb:

The floor should be dry, but in my understanding, a screed always has residual moisture for a long time.

So what? If the floor is ready for installation, then it’s ready for installation. Think about what you’re doing with the vapor barrier. The moisture you mention will cause long-lasting mold under the barrier ;-)

Just install the flooring and move on. Especially if the installer offers a warranty. I fully understand his points.

The DIN standards are not developed without reason; they are created by expert committees and are continuously, though gradually, adapted to current conditions. If a PE vapor barrier is required, it may serve more purposes than the ones you have assumed. A floating floor installation, as you described, might not slide well on a plain screed and could therefore warp. Also, consider why many buildings apply a bitumen membrane on the screed in the ground floor, even when using waterproof concrete. But for questions like these, we have a moderator and flooring expert here! (KlaRa) Just send a message...