Using Self Levelling Compound with UFH mats

[Richard Edwards]

Thanks Yorkshire T, appreciate the photos you've put up, great finish on that job
I checked the specs with Devimat & its totally waterproof including the cold tail. Im gonna be using Mapei keraquick flexible rapid set adhesive for the tiles so it should be fine.

Just a curious question, why isn't it wise to use slc on the decs? Is it because it would not maintain the preformed fall of dec an try & set horizontally?
regards

Hello AP

Re Not using SLC on a preformed wet room deck - This is as you have said. SLC wants to run dead level and unless you are very clever with it its not recommended as it will run to the drain and the fall will not be a fall at at all . Why interfere with the fall and gradients of a preformed deck - You buy these things to save you having to create the fall - Some decks are very low in gradients and being out by as little as 10mm can mean it will not work as a free draining shower but will resemble a continous puddle.

Re Excess cable - You could 'loose' the excess cable as you say - running it around the edge of room - ie outside the matt line as long as you do not reduce the 50mm clearance between cables - even cold tails.
The Devimat is in my opinion, the best or one of the best on the market - we always use them if we can.

Re Waterproof cables - suitability in wet rooms . Yes they are and are most suitable for wet rooms - no problems with that. I know YTS Yorkshire Tiling Services has posted an interesting and worthwhile post on how it can be done using flexible addy or a mix etc. I have no issue with that and only last week did a major remedial job on a 'disabled wet room' for a contractor who thought his lads could do it - and they clearly could not, and used the same / similar method as our YTS member. That said, I think that skimming a deck with heating cable under it is not recommended unless you have some experience. - Now, I still cannot see why anyone would want to install UFH on the deck ! It becomes warm the minute the shower is on and retains enough heat to dry it out afterwards.

Hope this gives you the answers you were looking for.

 

[ap222]

Thank you Richard & YTS for the extremely constructive comments and invaluable advice. Its really goes to show how little I know & how much more I can learn from experienced members like you on this forum

Before I joined, I knew little about tiling methods, substrate prep & so on, its being a great help joining this site.

regards

 

[doug boardley]

Hello AP

Re Not using SLC on a preformed wet room deck - This is as you have said. SLC wants to run dead level and unless you are very clever with it its not recommended as it will run to the drain and the fall will not be a fall at at all . Why interfere with the fall and gradients of a preformed deck - You buy these things to save you having to create the fall - Some decks are very low in gradients and being out by as little as 10mm can mean it will not work as a free draining shower but will resemble a continous puddle.

Re Excess cable - You could 'loose' the excess cable as you say - running it around the edge of room - ie outside the matt line as long as you do not reduce the 50mm clearance between cables - even cold tails.
The Devimat is in my opinion, the best or one of the best on the market - we always use them if we can.

Re Waterproof cables - suitability in wet rooms . Yes they are and are most suitable for wet rooms - no problems with that. I know YTS Yorkshire Tiling Services has posted an interesting and worthwhile post on how it can be done using flexible addy or a mix etc. I have no issue with that and only last week did a major remedial job on a 'disabled wet room' for a contractor who thought his lads could do it - and they clearly could not, and used the same / similar method as our YTS member. That said, I think that skimming a deck with heating cable under it is not recommended unless you have some experience. - Now, I still cannot see why anyone would want to install UFH on the deck ! It becomes warm the minute the shower is on and retains enough heat to dry it out afterwards.

Hope this gives you the answers you were looking for.

great post Richard, well explained

 

[The Legend; Phil Hobson RIP]

I asked Impey Tile safe technical dept this question last week. "can I lay ufh on top of tile safe"? the answer was "no" yet I have read somewhere that you can:dizzy2:

 

[ap222]

I asked Impey Tile safe technical dept this question last week. "can I lay ufh on top of tile safe"? the answer was "no" yet I have read somewhere that you can:dizzy2:

I guess it depends which UFH you install. Impey only recommend the Devi 100W, as other more powerful mats may damage the membrane.
When I emailed their technical, they advised me that it can be laid under the tilesafe, so long as you keep the mat 200mm away from the trap, as it could otherwise dry out the water within the trap.

 

[ap222]

I guess it depends which UFH you install. Impey only recommend the Devi 100W, as other more powerful mats may damage the membrane.
When I emailed their technical, they advised me that it can be laid under the tilesafe, so long as you keep the mat 200mm away from the trap, as it could otherwise dry out the water within the trap.

Sorry chaps, my post should have read "it can be laid over the tilesafe" and not "it can be laid under the tilesafe".

 

[wooferdog]

Hi guys, need some advice, i have laid ufh mats and covered with Sika latex, i know have discovered i should not have put this compound directly over the mats, rang Sika and they have told me the levelling compound may crack, any advice?

 

[grumpygrouter]

Hi guys, need some advice, i have laid ufh mats and covered with Sika latex, i know have discovered i should not have put this compound directly over the mats, rang Sika and they have told me the levelling compound may crack, any advice?

Stick to your original thread Wooferdog otherwise you will get dizzy flicking between the 2 for your answers.

 

[Richard Edwards]

Stick to your original thread Wooferdog otherwise you will get dizzy flicking between the 2 for your answers.

Not Sure if its OK to help you with this as Grumpy has put a caution there. Normally we would use Latex based SLC over heating mats so I am puzzled by Sika's Technical advise. It might be that they are being a bit over cautious - not sure. ! I would probably run it up to normal operating temp over a few days [increase by 10 C per 24 hrs as max, ] and allow a day to cool and as long as there are no major cracks and delamination I would tile over.

 

[wooferdog]

I have run the heating and no visible cracks so far, just to be over cautious i have laid ditra matting so if in the future it does detioriate the tiles have a chance of staying put or thats the theory.

thanks

 

[Dan]

Just bumping some threads in the underfloor heating forum. You can now find and search for both electric underfloor heating and water underfloor heating threads. By the way, if you feel some of the threads you want to be seen at the top of the forum need to be bumped back, for the next month or so from now, feel free to do that. Although it's not usually something we allow, whilst we're going through this process of changing over forum software, we see the need for this to happen.