Not gluing chipboard to joists - worst that can happen?

[gluecifer]

I have attached underfloor heating plates to a spaced panel across the joists and installed the tubing. The next step will be to screw down OSB boards over this. Now the spaced panel covers the joists as it is screwed across, but the plates also mean that I only have isolated spots on the spaced panel to apply glue for the OSB boards. If I had thought ahead, I could have placed the plates with gaps so that at least I could apply glue to the spaced panel right where the joists run underneath and where I will be screwing the OSB boards down through the spaced panel and into the joists.

What is the worst that could happen if I don't glue the OSB boards to the spaced panel? (The spaced panel is also not glued to the joists but screwed). Of course, I will glue the tongues of the boards to each other. I'm thinking that it might be enough to secure with plenty of screws both straight down through the spaced panel and into the joists, and also with shorter screws where there's only the spaced panel under the OSB. Fully glued gypsum boards with Ardex S48 will be placed on the OSB boards later.

 

[cffol]

I have attached underfloor heating plates on a sparse panel across the floor joists and inserted pipes. The next step will be to screw chipboard flooring over this. Now, the sparse panel covers the floor joists since it's screwed across, but the plates also mean I can only place glue on a few spots on the sparse panel for the chipboard flooring. If I had thought ahead, I could have spaced the plates so that it at least would be possible to place glue on the sparse panel exactly where the joists are underneath and where I'm going to screw the chipboard flooring down through the sparse panel and into the joists.

What's the worst that can happen if I don't glue the chipboard panels to the sparse panel? (The sparse panel is also not glued to the joists but screwed). Of course, I will glue the tongues of the boards to each other. I'm thinking that it might be enough to drive plenty of screws both straight down through the sparse panel and into the joists, as well as shorter screws where there is only sparse panel under the chipboard. It will be fully glued gypsum boards with Ardex S48 on the chipboard later.

What is the intended final surface layer? And how large is the area? If I understand correctly, the construction is intended to be sparse-chipboard-gypsum-surface layer? It doesn't sound entirely optimal from a heat transfer perspective for the underfloor heating, as both chipboard and gypsum insulate quite a bit. Regarding whether to glue or not, it will of course work without you gluing down everywhere (at least glue between the boards), but there may be a slightly higher risk for creaking over time. But it also depends on the final surface layer.

 

[gluecifer]

Thanks for the response. It will probably be tiles on top, I am aware that it will be sluggish, etc., but the conservatory (30sqm) in question is quite well insulated with winter sections, roof, etc., and we have a heat pump to top it up with. It'll work
But you don't think the floor itself will move or whatever might occur due to not being glued to the joists? Squeaking might happen, but I'd prefer that over larger movements?

 

[cffol]

Thanks for the response. It'll likely be tiles on top, I'm aware it might be sluggish, etc., but the conservatory (30 sqm) we're talking about is quite well insulated with winter glazing, roof, etc., and we have an air source heat pump to top it off. It should work
But you don't think the floor itself will move or that something similar might occur because it's not glued to the joists? There might be some creaking, but better that than major movements, right?

It'll be pretty dead with the plaster, so I would say it's unlikely that there will be cracks between the tiles (which I assume is what you want to avoid) due to movements just because you're not gluing down the chipboard. Just make sure the joints between the different layers are staggered.
Then, it's not exactly heat-retentive, but rather well-insulated heat distribution, so it will be difficult to actually get much heat on the floor. You'll need a higher supply temperature, which affects the rest of the system. It's good to have an ASHP to get a higher temperature in the room, but as mentioned, the floor won't likely feel warm and cozy unless you have a supply temperature around 45-50 degrees.

I have a solid wood floor that's 21 mm with underfloor heating myself, but in the hallway, it's chipboard and 10 mm marmoleum instead—very big difference in perceived floor temperature despite having the same supply temperature and even the same pipe loop in some areas. In the kitchen and bathroom, the pipes are embedded, and the surface is stone, and it's even warmer there on the floor surface.

 

[gluecifer]

Ok! Do you think there will be a noticeable improvement in the floor heating if you had used 13-15mm of leveling compound on the chipboard instead of plastering? Or does it come out the same way?

 

[cffol]

Ok! Do you think there will be a noticeable improvement in floor heating if you had poured 13-15mm of leveling compound on the chipboard instead of using gypsum? Or is it about the same?

There will probably be an improvement (since the leveling compound conducts heat better than gypsum), but the question is if it's worth the effort. The best solution, but I understand you've already laid the battens, would of course have been to start with chipboard for load-bearing capacity, then add pipes and leveling compound or alternatively battens and plates.

 

[imported_Benno]

Maybe a late reply but. I have never glued down subfloor boards to the joists. What would be the point of that? If you ever need to open the floor, it just becomes more cumbersome.
I have spaced paneling and sheets under the subfloor boards. Felt paper and 16mm oak parquet on top of that. Has worked excellently for 15 years now.

 

[Anonymiserad 282191]

Maybe a late answer but. I have never glued the floor chipboard to the joists. What would that be good for? If you ever need to open up the floor, it just becomes more troublesome.
I have sparse panels and sheets under the floor chipboard. Paper and 16mm oak parquet on top. Has worked excellently for 15 years now.

You glue to minimize the risk of creaking in the floor against the joists.

 

[Pumabjörnen]

The glue on the floor joists is meant to reduce creaking and, for construction purposes, increase the stiffness of the floor structure by enhancing the interaction between joists and chipboard.

Isn't it an option to screw down the plates and then use construction adhesive on the furring strips/plates instead of wood glue?