Hairline craks in SLC

[vrytir]

Hi guys,

I came with another problem. I use mapei Ultraplan renovation screed to self level my floor with cable UFH. And now I found hairline cracks in it. Does it mean my subfloor was not good enought and I can start again or is it normal.
Subfloor is WBP 18mm, mapei ultraflex, 6mm insulation board, then the UFH cables and now screed. I put quite a lot of noggins when installing WBP.

For the floor it will be ceramic tiles 300x300, using mapei ultraflex as adhesive. Not sure about grout, is there some "flexible grout"?
Or do I have to start again from scratch?

What is you opinions, please?

 

[DHTiling]

How thick did you use it and did you prime.. ?

 

[vrytir]

I prime it with Primer G and it is about 10mm-12mm thick. This ultraplan screed could be up to 30mm thick.

 

[DHTiling]

Ok, how much water did you add. ?

And is there any deflection in the substrate..?

 

[vrytir]

It was 4.5l per 25kg bag and deflection? Well I am big guy 20st roughly and when I put my laser leveller on the WBP there was some movement, but when my better half did the same there was just slight move.

 

[DHTiling]

I think that could be the issue.

How soon did you walk on the floor after levelling.

 

[vrytir]

I left it about 24 hours to dry. Mapei recommend 4-5 hours.

 

[charlie1]

Think mapei recommend using eco prime, unsure if this would be a factor in what's happened though

 

[Ajax123]

Could just be drying shrinkage. Pictures might help

 

[vrytir]

Could just be drying shrinkage. Pictures might help

I hope :smilewinkgrin:

I try to get pictures tomorrow.

 

[Rookery]

Have you switched the ufh on?

 

[vrytir]

Have you switched the ufh on?

No, I didnt

 

[Gazzer]

Did it crack before or after you walked on it and are the cracks in straight lines or squiggly ?

 

[Stu Lilley]

We supply and use this all the time and over timber Eco Prim Grip must be used,,,i did talk to the tech guys this week and Eco Prim grip gives a chemical and mechanical bond to what ever you apply it to,,,Primer G would not have been man enough to use over WPB

 

[nybor62]

throw a tarpaulin over it you wont see the cracks, :smilewinkgrin::smilewinkgrin:

 

[vrytir]

Did it crack before or after you walked on it and are the cracks in straight lines or squiggly ?

I think it cracked when I walked on it, but I am not 100% sure.
Cracks are squiggly.

 

[vrytir]

and the pictures

 

[big george]

are the cracks starting from the same point on the floor? could be a weakness at that point

 

[Ajax123]

and the pictures
View attachment 51194View attachment 51195View attachment 51196

Those are most definitely drying shrinkage cracks. Possibly the substrate has sucked the moisture out too quick, possibly it has evaporated too quick. You can repair them with a low viscosity epoxy resin but don't other until after you have run the underfloor heating through its heating cycle.

 

[DHTiling]

If it is hollow to tap , then it is goosed..

 

[White Room]

As above, sounds like it's blown considering it cracked when you walked on it....

 

[enduro]

Got cracks in my hairline..:yikes:

 

[Ajax123]

Got cracks in my hairline..:yikes:

Think yourself lucky.... I haven't even got hair in my hairline anymore 😉

 

[Mark S]

Looks like a combination of shrinkage cracks and movement in the boards, as with Dave, does it sound hollow when tapped?, coz thats a whole new ball game.

 

[vrytir]

, does it sound hollow when tapped?,

No, it doesnt sound hollow when tapped.

 

[vrytir]

Should I tile on it?

 

[DHTiling]

In all honesty .. NO..

 

[vrytir]

So should I take it apart and start again:yikes: I plan to use mapei ultraflex adhesive, which is super flexible, wouldn't this help?

 

[vrytir]

Or could I put another layer of SLC? Would this help?
I also find that current layer of SLC is kind of "AERO chocolate" bubbly, I guest this is problem.:mad2:
Would another layer of SLC sort both problems (bubbles and cracks)? And then use Mapei Ultraflex adhesive.

 

[DHTiling]

You not tiled it yet then 🙂

 

[vrytir]

I am a little bit slow:8: My missus is getting mad at me. I have no idea why:smilewinkgrin: