Levelling with ufh

[joshtiler]

Evening all just a quick question, I have a bathroom floor to do (when I have done the walls) the floor is a screed and It needs some slc. It has a ufh mat to go down but what I was wondering is should I level the floor, then lay the mat, then put slc over the top of the mat or can I lay the mat on the un-levelled screed and lay the slc over it? The slc i have got is weber, I need to keep the height as low as possible as the tiles have to finish flush with top of shower tray, when I lay the slc over the mat can I just lay enough to cover the elements or does the mat have to be set in a certain thickness of slc? Thanks. Josh

 

[Ian]

Are you not putting an insulation board down Josh?

 

[Ajax123]

Ditto Bri...

 

[Rookery]

Ditto ditto

 

[joshtiler]

Do you mean like a marmox or hardibacker board mate? I didnt think I needed to as it was on a screed? I did upstairs ontop of the ply but on the box the diagram shows the mat going straight onto the screed?

 

[cam_low]

As above, above and above lol

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Are you being paid to do this job or is it your own house?

 

[trevortine]

The screed will just suck up all the heat, stick down some insulation boards with flexi adhesive, lay your UHF then screed over, just above cable height is fine. Take time to ensure matting and cables are properly fixed to boards to avoid them rising in sic.

 

[Ajax123]

The screed will just suck up all the heat, stick down some insulation boards with flexi adhesive, lay your UHF then screed over, just above cable height is fine. Take time to ensure matting and cables are properly fixed to boards to avoid them rising in sic.

And once again ditto

 

[AliGage]

Ditto ditto ditto

Can someone find the link to whitebeams (i think) post/guide to laying UFH. Very useful.

 

[joshtiler]

Sorry guys I was driving

Cam low yes it's someone's house mate and I hope I'm being paid haha!!

Trevortine by insulation board do you mean like a hardibacker?

I have never put a board down on a screed before? The manual says that putting it onto a screed is fine and when I went to a trade day the rep from rachem said it was fine also? I am not suggesting that any of you are wrong I trust your experiance 100% but have I been doing it wrong all this time?

 

[Ian]

Here you go Josh, an awesome tilers forum member did this thread a while back http://www.tilersforums.com/electri...ng-electric-underfloor-heating-step-step.html

 

[joshtiler]

Thanks alot bri I will give this a read now I've put little man to bed thing is I've installed the mats on to screeds before and never laid a board down? I can see why you do and when I lay one onto a timber floors I always put a hardie board onto the ply. Does it vary depending in what brand of mat it is to weather you need to board it? As I said the manual and the rep said straight onto a screed is fine? I'm confused lol

 

[Ian]

The insulation is a must, otherwise you will be heating 100mm + of concrete as well as trying to heat the floor/room. Very expensive running costs as well.

 

[joshtiler]

The awesome tilers forum member was you lol!!! Ok mate what is the minimum thickness of board you can put down as I have very little to play with?

 

[Dougs Third Go]

the thicker the better, but even 6mm is better than nowt.

 

[joshtiler]

Thanks mate I think on this occasion it will have to be 6mm. But in future I will lay it this way. It has blown my mind a bit though as in the installation guide there is no mention of putting a board down?? Weird

 

[Ian]

They've probably got a deal with the electric companies, the reps get a cut!

 

[joshtiler]

Haha I recon you could be right mate!! Other than the obvious heat loss through the concrete screed will not putting a board down effect any aspect of the actual tiling? As I said I have do e a few and am now worried will the tile/ufh fail without the board?

 

[Dougs Third Go]

it won't fail without the board,,,just be damned expensive to run!

 

[AliGage]

Here you go Josh, an awesome tilers forum member did this thread a while back http://www.tilersforums.com/electri...ng-electric-underfloor-heating-step-step.html

Sorry Bri mate. I didn't have time to go look for it. I was debating between the two of you.

Thanks mate I think on this occasion it will have to be 6mm.

The manufacturers installation instruction will more than likely specify the use of an insulation board. The likes of Warm up even tell you the minimum thickness (10mm with them). I don't know where you would stand on warrantys in the event any do fail.

 

[Ian]

Haha I recon you could be right mate!! Other than the obvious heat loss through the concrete screed will not putting a board down effect any aspect of the actual tiling? As I said I have do e a few and am now worried will the tile/ufh fail without the board?

It won't fail, it just won't be very efficient.

 

[joshtiler]

Thanks mate put my mind at rest I will always put board down from now on

 

[Ian]

Sorry Doug, you're post wasn't there when I started writing! Got sidetracked by a packet of foxes crunch creams!

 

[Protilers]

6mm board is fine........(and has insulation properties v. similar of 10mm!) but level the floor first.....then lay insulation......then level again and tile.......this way you get the most heat transfer.......all the best

 

[joshtiler]

Thanks all of you for advice

Aligage this is the installation guide mate it's a brand called rachem (from CTD) there are alot of pages but the instructions that come with the mat I get are from page 21 and it says subfloor, then mat, then tile adhesive, then tile it doesnt even mention slc either? Not saying you any of you are wrong as I see how it would be costly to run but just wanted you to see what I have got to follow lol!!

Here it is:
http://ru-ru.thermal.pentair.com/Images/EN-RaychemFloorheating-TH-CDE0695_tcm506-35938.pdf