825x550x20 limestone on underfloor heated suspended 12mm ply

[Fraser]

Hang on Fraser could you tell me the spec of the floor... so this is wet ufh?

Hello CR,
I was told earlier today, its UFH system laid in plastic trays, with an unspecified joist width, with a builder that was insisting it had a maximum of a 12mm ply over the top.
The tile to be laid is 825x550x20 limestone tile from Mandarin stone. Obviously I was keen to know who would specify 12mm ply as a substrate.
I was introduced to Nicobonds "Plastic Ply", http://www.nicobond.com/files/Information_Sheet.pdf and wondered if a solution could be found combining these products.
After going to the site this evening, the wet system is the problem, and trying to skimp on floor height with substrate isnt the answer.

The builder was still on site after 6.30pm, very irate after trying to remove enough screed to accomodate a wet UFh system over 56 metres of floor.
In places, the floor has lost over 200mm of screed! When I asked why and electric syem wasnt installed, the customer said it was expensive to run.
I told them that the electric system should be used, and wished the builder good luck re screeding the floor.

I left it in the customers hands and await a reply.

 

[Fraser]

Hang on Fraser could you tell me the spec of the floor... so this is wet ufh?

yes a wet system

 

[bugs183]

These systems are spec'd like this by a couple of manufacturers and suggest the thermal boards are loose laid or screwed, then after the pipes are inserted two layers of cross bonded 6mm ply are loose laid on top then tiled with flexible adhesive.
No no no!!! What an awful system.
I've encountered a few and the only way i would tile them is to fix the thermal boards down with adhesive and screws. Lay the pipes then Level over the whole system, then Ditra over the whole floor. Then fix the tiles.
Any less than that is seriously asking for trouble Fraser.

 

[Fraser]

These systems are spec'd like this by a couple of manufacturers and suggest the thermal boards are loose laid or screwed, then after the pipes are inserted two layers of cross bonded 6mm ply are loose laid on top then tiled with flexible adhesive.
No no no!!! What an awful system.
I've encountered a few and the only way i would tile them is to fix the thermal boards down with adhesive and screws. Lay the pipes then Level over the whole system, then Ditra over the whole floor. Then fix the tiles.
Any less than that is seriously asking for trouble Fraser.

wow, thats different, didn't even consider that as an option, have you tried it before?
What depth of bed of flexible leveling did you use, what kind of adhesive, SPf or 2 part?
My concerns are the strength in the floor and weight being taken on the plastic pipe trays

 

[Colour Republic]

Hello fellas,

I have a customer wanting to fix 825x550x20 limestone tiles on underfloor heated, suspended 12mm ply floor.

So you didn't mean a suspended floor as per your first post. You meant a floating floor?

 

[bugs183]

I've done it once.
A friend of mine was saying how brilliant this new system was and that he was using it on my next job, and that he thought i could tile directly to the boards with no ply etc.
I check with the Tech Dept and couldn't believe the non sense they told me regarding the 6mm plywood.
He said it's too late, it has to be tiled, so i devised the above method.
It has worked, but i'll never tile another job using this u/f/h/ system, way too dodgy.

 

[Ajax123]

Hello Ajax, thanks for your reply. So you suggest to walk away? Surely a simple letter waiving responsibilty for defects due to movement would suffice in court?
Or do you believe you have a solution to the above problem? H
"Do it right" isn't a solution.

Sadly not mate. A proper legally binding disclaimer is likely to b ten or twelve pages long and will need to be written in legal terms. You are the expert in the client tiler relationship and as dave Howe has said if you knowingly do it wrong you would be liable. Sorry

 

[Ajax123]

Hello Ajax, thanks for your reply. So you suggest to walk away? Surely a simple letter waiving responsibilty for defects due to movement would suffice in court?
Or do you believe you have a solution to the above problem? H
"Do it right" isn't a solution.

Sadly not mate. A proper legally binding disclaimer is likely to b ten or twelve pages long and will need to be written in legal terms. You are the expert in the client tiler relationship and as dave Howe has said if you knowingly do it wrong you would be liable. Sorry

 

[Rookery]

And just to help you come to the right decision, when/if the floor fails, you will be held liable and be responsible for all the costs incurred in the remedial works. I would thank them for the opportunity to quote but would turn the job down.

 

[Fraser]

So you didn't mean a suspended floor as per your first post. You meant a floating floor?

yeah, sorry, it rests on the trays and is fixed to joists, spans 670mm between inlaid timber.

Bugs183, trust me, after the last one I was made to do, I'll make sure I'm happy with this one.
Cheer for your help anyway.