Floating Screed - Tile Advice

[Claude]

Hello,

My first post: I was wondering if anybody can give me some opinions on this forum. I have recently purchased a house in Luxembourg. I have tried to contact local professionals but I was not able to get a satisfactory answer from any of them.

I am installing a walk in shower on the top floor of a timber structured house. The room contains a floating, cast asphalt screed over an OSB floor fixed to the beams underneath. Dry walls are installed already in the corners of the floating screed, but are actually resting on the floating screed itself (which basically is extending to the adjoining rooms on the otherside of the walls)

I have cut a 1200X1200 square off the floating screed in the corner, with the plan to drop in a Jackboard or Wedi tray. i have also removed the drywall gypsium sections on these existing walls with plans to replace with Jackoboard of equivalent thickness. I am hoping that in this manner i will be able to successfully bond and seal the tray to the adjoining walls.

My worry is the following: I have the walls resting on the floating screed. The Wedi or Jackoboard tray has instructions to fix firmly to the OSB floor, hence it will not be floating. I am wondering whether this will eventually result in problems.

So far I see the following solutions:

1. Remove the walls completely and reinstall directly onto the OSB substructure. This will be a massive expense and i'd like to avoid if possible.
2. Drop in the jackoboard tray and ensure the seals between this and the surrounding floating screed is well flexible.
3. Have the Jackoboard tray float together with the screed. This goes against all instructions I found so far, but I'm wondering if with the structure I have, if this is actually the best solution.

thanks in advance for any advice!

Claude

 

[Ajax123]

Is it floating or is it unbonded. Floating means on insulation. If this is the case I think it presents some risk particularly if the insulation is not rigid enough. It will bounce and ultimately the joint between floors and walls may open up causing a leak. If its unbonded that's a better option as the walls and subfloor are then supported in the structure rather than on a spongy layer of insulation.

Either way you ideally need the floors and walls to act as compositely as possible. Personally I'd look at ignoring the existing walls and putting in a false shell fixed down to the osb subfloor and have it more like a free standing cubicle if you get what I mean.

 

[Claude]

Thanks for that. It is along the lines of what I was thinking, but the problem remains on how to fix the cubicle walls to the actual wall frame...

It's definatsly floating. A layer of perlite followed by some insulation board, then mastic asphalt.

I'm attaching a couple of photos to show more clearly what I have. Unfortunately the plumbing and hole are already done. Starting to think I should have probably abandoned the idea of a walking shower and install an acrylic tray instead...

Any ideas on how to tank this beast?

 

[Claude]

Thinking further about this, I am thinking of cutting back a couple of cm of the insulation and perlite and injecting either silicone or flex tile adhesive to effectively bridge the Asphalt screed to the OSB below, effectively creating a more solid place into which to drop in the Wedi/Jackoboard tray. This will help with the sealing and also with the stability of the screed. Would you recommend this and if so, would it be best to use Silicone to allow for more movement, or tile adhesive so as to make things more rigid and less prone to cracks in the future? Both solutions seem to have pros and cons.

 

[Claude]

bump
Any ideas on this one? I haven't come up with any brighter ideas so far.
thanks!
Claude