how to best fix stone directly over water underfloor heating pipes.

[jonnyc]

Ive just seen a job , where the make up of existing floor is : beam and block floor,insulation and then screed on top.
the builder then loose laid the underfloor water fed heating pipes on top of screed ,fixing wooden battens between the pipes so that they could screw the wood floor down on top.
wood floor has been down thirteen years now and new owner has decided she would like to lay limestone down instead of wood.
I have never been asked to do this before and am interested to know if anyone else laid overa subfloor like this and how they prepared it.
Another tile company laid limestone in hall over pipes and it hasnt cracked , but client not sure what they did to prepare.
my first thought was possibly screw fix plywood over heat pipes in to existing battens as one would do with a supended floor where pipes are set in metal trays between joists.in that scenario one would screw plywood in to joists instead of battens in thise case.
then ditra mat over plywood and lay tiles. I would have to put a disclaimer in about ply over water pipes as schluter now say ditra should not be laid on ply over water underfloor heating.there is also the problem of not being able to screw the boards down along all edges as battens only run in paralell.
so not ideal really but if a client is insistent and will not blame me if floor cracks an option i suppose.
the other option i guess could be remove battens and then lay another screed over pipes .
but how thick should screed be and is this even an answer to problem. would then lay ditra mat over new screed .

either way this will bring up floor levels some.

would be grateful for any ideas.

 

[DHTiling]

Re: how to best fix stone directly over water underfloor heating pipe

Hi Jonny.. what sub-floor is down now.? and joist centres ?

 

[jonnyc]

Re: how to best fix stone directly over water underfloor heating pipe

dave thanks for response.
i am acually very dissapointed that 40 people have had a look at this thread but you are the first to get involved.
i may not have written it very well, hence no response.
but the make up of floor i am talking about is beam and block, insulation and screed on top of that.
then water fed pipes loose laid on top of screed.
i may have confused my explanations by talking about suspended sub floors but i was only making a comparison.
any ideas welcome

 

[DHTiling]

Re: how to best fix stone directly over water underfloor heating pipe

Ye i got that bit.. what has been used to over board onto the timber lats?.. and deflection.?


I did an up stairs one and it was ply'd , so i used hardi 250 and Ditra.. worked great.. the hardi has low UV , so didn;t interfere with heat.

 

[jonnyc]

Re: how to best fix stone directly over water underfloor heating pipe

as far as i know . the timber oak boards are just nailed or screwed in to the battens.there is no plywood base screwed to battens first.

 

[DHTiling]

Mmm not a base I would be happy with.

As we cannot see what you do mate , it is a difficult call.

You have more expansion / contraction as you know , with that type of covering and depending on batten centres more movement Deflection wise.

 

[The D]

Re: how to best fix stone directly over water underfloor heating pipe

I would call one of the adhesive manufacturers for a specification you may be able to get a rep out to do you a spec but it is a hard one to call as Dave has said.

 

[The D]

Re: how to best fix stone directly over water underfloor heating pipe

It may be an option to use a suitable SLC then maybe something like hardy backer .just a taught but I would still ask the question

 

[jonnyc]

Re: how to best fix stone directly over water underfloor heating pipe

well i spoke to adhesive manufacturers today and its a big no no all round.
i think the only way out is to cut off the water underfloor heating, thereby gaining 20-25mm and then laying
dukkaboard or similar on screed and do electrical heating.
there is a chance this way of still being able to come in at a level that allows appliances to still come out.
very expensive option but i am just not prepared to lay this stone floor over heat pipes directly underneath even if i can put in a disclaimer .
the real problem is that another stone company did a small hallway by latexing to top of pipes and ditra and stone has not cracked , so client thinks there is little chance of kitchen /conservatory stone cracking.
but this is a much bigger area and sometimes i think you have to just step back and say no even if the job is well worth doing.
the agro and cost to dig this up if it does fail will be very big.
you said no to a client deano little while back , i saw in a thread and sometimes you just know it could all end up in tears.
other times i get asked to do work that is not strictly done by the book ie mixing sand/cement/adhesive for bedding old reclaimed stone of different thickness but i know that this method works and has never failed .
i put a disclaimer in but can assure client it works and worth doing this way.
so i may lose the job and have invited client to get other tilers in to quote to get a comparison as i always do anyway.

 

[DHTiling]

Re: how to best fix stone directly over water underfloor heating pipe

I think you are right, sometimes you just have to admit,, no it should not be done..