Cracked mapei revonation screed - TilersForums.com

[Jimwilts]

Hi all, i posted this on the underfloor heating forum, but have had no reply yet.


last week I laid loose wire UFH on top of cement insulation boards, and then laid mapei renovation screed over the top. I went back today, and all seems well apart from one area that has only just covered the loose wire and the tape that was holding the wire down. As a result this area of SLC has airlined on top of the UFH cable. The SLC has bonded well to the insulation boards.


Do you think I should lay another layer of SLC on top, Or is it OK to tile over the top?


BTW, I'm laying 30x30 gulf stone using mapei granirapid adhesive.


Thanks in advance
jim

 

[Dan]

You can tile it as it is, just go very very steady over the cables for obvious reasons.

You can actually tile directly over lose cable but clearly it would be a bit of a nightmare to do and you risk damaging the cable, but it is possible.

If you feel safer using more SLC, then fire away, but if it's just a smallish area of cables showing through, then I think I'd just tile it as is.

 

[Jimwilts]

You can tile it as it is, just go very very steady over the cables for obvious reasons.

You can actually tile directly over lose cable but clearly it would be a bit of a nightmare to do and you risk damaging the cable, but it is possible.

If you feel safer using more SLC, then fire away, but if it's just a smallish area of cables showing through, then I think I'd just tile it as is.

Thanks for your reply Dan.

its the first time I've used mapei renovation screed, and I was surprised how flat it went down with little trowelling. I did use a roller on it also. I get the feeling i laid it to thin over the sticky tape.

Is it common for renovation screed to crack over loose wire which has been laid on insulation boards?

regards
jim

 

[Martyn Leeds]

Opinions would be heresay, I'd perhaps phone Mapei Technical...

 

[Dan]

Got any pictures?

If the cable has moved during it curing, it would cause cracking. Depends what's going on though. Pictures might show it better.

 

[Gazzer]

Its not usual for it to crack at all....the under floor heating cables were not working at the time were they ?

 

[Jimwilts]

Got any pictures?

If the cable has moved during it curing, it would cause cracking. Depends what's going on though. Pictures might show it better.

No, no photos at the moment. They are very thin airlines that follow the loose wire UFH.

 

[Jimwilts]

Its not usual for it to crack at all....the under floor heating cables were not working at the time were they ?

no, they wasn't working, just tested before SLC

 

[Jimwilts]

Got any pictures?

If the cable has moved during it curing, it would cause cracking. Depends what's going on though. Pictures might show it better.

I poured on the friday morning and came back on monday. Customer was home working in the kitchen area over the weekend. Customer has a de humidifier but I'm not sure they had it on.

 

[CJ]

If the floor had been walked on after the self level has dried, then yes it would cause slight cracking around the cables. Due to the cable being pushed into the insulation panels slightly.

 

[Jimwilts]

If the floor had been walked on after the self level has dried, then yes it would cause slight cracking around the cables. Due to the cable being pushed into the insulation panels slightly.

Thanks for that.

I was thinking the same thing as the airline is directly on top of the cable/tape. I do regret covering all the cable in tape though, but i didn't want the cable to float during levelling.

Im not tiling it until the new year, after they have turned the heating on. Time will tell!

Thanks for all your replies.

 

[Stef]

Thanks for that.

I was thinking the same thing as the airline is directly on top of the cable/tape. I do regret covering all the cable in tape though, but i didn't want the cable to float during levelling.

Im not tiling it until the new year, after they have turned the heating on. Time will tell!

Thanks for all your replies.

What kind of tape did you use?
If the tapes got a shiny surface like Gaffa tape then the slc won't have taken to it.

 

[Jimwilts]

What kind of tape did you use?
If the tapes got a shiny surface like Gaffa tape then the slc won't have taken to it.

Gaffa!

 

[Stef]

Gaffa!

If the slc isn't very thick over the wire then you could tease some of it off the top as it sounds like it hasn't stuck to the tape.
Personally I wouldn't worry about it as it will be fine once you spread your addy on the floor.
Buy a glue gun & try that next time.
I've used hundreds of bags of renovation screed & have never had a problem with it,
It flows really nice & you can almost get it perfect in one application.