Glue Double Gypsum (Floor)

[Kojfabriken]

I agree (even though I haven't tried it myself).
But not simple wallpaper paste, which is just starch and easily soluble if it gets damp.
But fabric glue/wet room adhesive? Maybe this:
[link]

Well, I'm also wondering if moisture could cause problems, or movement. Movement does exist in wooden walls, yet the wallpaper stays just as immovable. Moisture might indeed cause issues, but if water gets into the layer between two gypsum boards with fix and tiles on them, it feels like it must be quite a significant leak, especially if there is underfloor heating which helps with drying.

Wet room adhesive doesn't sound too bad otherwise, and with a consumption of one liter per four m2 (and not the other way around), it becomes economical too.

 

[RiKr]

If you have time, could you make a sample piece with wallpaper paste, provided you have it at home.

 

[Kojfabriken]

I have glued plasterboards with vinyl acetate suspension, i.e., regular white glue/wood glue. Incidentally, it is the chemical basis for the "primer" you should apply to plasterboards before you tile or apply rolled waterproofing layers.

Yes, I have read that some have used that as well. How much is needed per m2? Can it be diluted with water to brush it out? I imagine it's a bit thick if you want to achieve an even layer.

 

[Kojfabriken]

If you have time, could you make a test piece with wallpaper paste, assuming you have that at home.

Well, I was actually considering that earlier today, I have some old plaster scraps in the garage and we should have a small jar of wallpaper paste left from when we made homemade lampshades a few years ago.

 

[RoBo]

Imagine if you hired a craftsman who started tinkering with something other than Ardex. What a fuss that would cause on the forum. I don't understand what the difference is, shouldn't one do it right even as an amateur?

 

[Kojfabriken]

Imagine if you hired a craftsman who started tinkering with something other than Ardex. What a fuss there would be on the forum. I don't understand what the difference is, shouldn't you do it right even as an amateur.

I'm sure there is. Certainly not wallpaper glue, but the question is primarily technically interesting to investigate.

 

[KnockOnWood]

Wet room adhesive doesn't sound too bad otherwise

Note that the wet room adhesive is specifically designed to bond two materials/surfaces with very low absorbency.
Check the instructions carefully, it's important to let the adhesive dry a bit before putting the surfaces together.

 

[Claes Sörmland]

Otherwise, KNAUF PERLFIX T gypsum adhesive 25 kg seems economical and ideal for the purpose. A gypsum mortar instead of a cement mortar like Ardex S48. Byggmax sells a competitor called Megaron Gl 5, which is also a gypsum mortar. Gyproc sells its G 66 Gypsum Mortar for the purpose. But when I read the instructions, it's not suitable for bonding panels on the floor, only for walls. Doesn't the mortar bear the load that occurs on floors?

 

[Claes Sörmland]

Gyproc sells g46 for gluing plasterboards (also on floors). It is quite expensive. What does it contain then? Well, it is a polymer of ethylene vinyl acetate (EVA) mixed with chalk as a filler.

Gyproc states that the ends of the boards should be glued generously with regular PVA glue (white glue/wood glue). The difference between cured EVA and PVA is that EVA is slightly more rubber-like. Furthermore, PVA is sensitive to water. That is, the board adhesive contains chalk as a filler to maintain volume even after it has cured and is more rubber-like than dried wood glue.

 

[nino]

Does it really work to glue floor gypsum directly onto sparse, the second layer should work well but what about the first?

 

[Kojfabriken]

Does it really work to glue floor gypsum directly onto sparse, the second layer is likely to work well but how does it work with the first layer?

Gyproc sells g46 to glue gypsum boards (even in flooring). It is quite expensive. What does it contain then? Well, it is a polymer of ethylene vinyl acetate (EVA) mixed with chalk as filler.

Gyproc states that the ends of the boards should be glued with plenty of regular PVA glue (white glue/wood glue). The difference between cured EVA and PVA is that EVA is a bit more rubber-like. PVA is also water-sensitive. That means the board glue contains chalk as filler to provide volume even after it has cured and is more rubbery than dried wood glue.

Interesting! Thanks for all the input Claes,

It's typical that what works for flooring still costs quite a bit. . I guess starch-based glue would have the same problem with load. Primer and adhesive are probably the economical option in the end.

 

[Kojfabriken]

Does it really work to glue floor gypsum directly to sparsely laid boards? The second layer might work well, but what about the first?

Nah, the first one I just planned to screw. There will be underfloor heating plates there, so gluing isn't an option anyway. I've asked others about that issue. Many people lay down a floor chipboard and then only one layer of gypsum, but chipboard is said to make it heat resistant. I think it was AndersS who mentioned using 22mm chipboard as well, which the carpenter who later visited considered unnecessary since there's already a 50mm layer that is supposed to hold together.

But of course, you might think that gypsum screwed to a sparse panel could potentially be pulverized around the screws under load? I wonder if I should throw in a thinner plywood on top to have something to glue to :/

 

[nino]

With ardex, you roll the sheets with 7+8 so it's possible to glue, the sheets are of course screwed first.

I wouldn't trust a screwed plasterboard, the slightest flex and the screw gnaws through the plaster...

22 chipboard and plasterboard, then you know it holds.
Underfloor heating in itself is slow, and one 22 chipboard more or less, I think it doesn't matter.

 

[Andreas_kalmar]

If you care about the effect, then self-leveling compound is probably better than gypsum.

 

[Kojfabriken]

With ardex, you roll the sheets with 7+8, so it's possible to glue, the sheets are screwed first, of course.

I wouldn't trust a screwed gypsum, slightest flex and the screw gnaws through the gypsum...

22 chipboard and gypsum, then you know it holds.
Underfloor heating itself is slow, and one more or less 22 chipboard, I think doesn't matter

Really!!? So you can also glue the sheets. That definitely sounds wise as it creates more of a unified structure with all the layers that need to be included. I don't understand what 7+8 means!? Is it another chemical you roll on first?