Should vapor barrier film be glued under laminate?

Hello,

I want to lay laminate on the screed (with underfloor heating) in the basement. I saw a note with the laminate that when dealing with a "mineral substrate," a vapor barrier (I think 0.2mm PE foil) should be laid underneath.

a) Does the foil have to be sealed airtight at the joints with adhesive tape (like with a vapor barrier/vapor retarder on the roof)?

b) Should/might the foil also be pulled up on the sides of the walls under the skirting boards and possibly also be sealed (...like on the roof)?

Thank you very much for your answers

The foil must be laid with sufficient overlap (about 20 cm) and pulled up at the edge. Adhesion is necessary; otherwise, the entire construction would not be truly vapor-tight. You should choose the appropriate tape for this and not just any tape that happens to be around. More details (which foil, which tape, and which impact sound insulation are suitable for your purpose) will be provided by a specialist retailer; I am also just an amateur who plans to lay laminate flooring myself soon. There are also combination products for vapor barriers and impact sound insulation, but these are also taped at the transitions.

Decisive for the suitability of the flooring for underfloor heating is, on the one hand, the thickness of the material, and on the other hand, its thermal conductivity. These two factors determine the thermal resistance (WDLW) – the lower this is, the better for the combination with underfloor heating. The thermal resistance of 0.15 m²K/W must not be exceeded. Laminate with a thickness of 9 millimeters has a thermal resistance of about 0.044 m²K/W. The laminate must be explicitly marked and approved by the manufacturer with the indication of the WDLW for installation over underfloor heating. If "Trittschalldämmfolien" are additionally installed underneath, their WDLW must also be added.

What is the purpose of the vapor barrier? Should it prevent moisture from below from penetrating into the laminate, or should it prevent moisture from the room air from diffusing into the floor construction due to vapor pressure? The floor construction up to the raw ceiling/floor slab/, including the connection to the rising masonry or WW, including building sealing and insulation, should be known before deciding on such a detail.

I would like to start here. We plan to lay "click laminate" in the attic hallway and bedroom. It is said that on mineral floors and/or underfloor heating with warm water, a vapor barrier must be installed. Nowadays, there are countless 2-in-1 products, impact sound insulation + vapor barrier, but we would like to avoid the aluminum layer. However, I don’t want to first stick PE foil and then lay normal impact sound insulation on top. Are there also 2-in-1 products without an aluminum layer? Thanks in advance.

Just have a look on the websites of various manufacturers (Logoklic, Parador...) because you could write entire novels about that.

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