UFH screed showing few cracks, is Ditra Mat essential ?? - TilersForums.com

[Boom]

Hi need advice. We had the wet UFH done topped with screed. Been a month since the screed was done. Cracks have appeared at a few places. Is putting Ditra Mat absolutely essential ?? Will it affect the heat coming up from the UFH ?? Do the cracks need to be fixed ??
Thanks

 

[Dan]

Have you got any pictures?

What depth is the screed? And how much of it is above the UFH?

I'd say some form of anti crack matting is essential there. Your adhesive and then tile will just follow the cracks.

Depends on how deep they are and where they are as go what's caused them I guess.

Do they follow the UFH?

 

[Boom]

Attaching the pics of cracks below
They are quite prominent near door areas. The screed is 70 mm

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[Time's Ran Out]

What tile is going down?

 

[Bond]

What type of screed is it.

 

[Chalker]

Has the ufh been on yet?

 

[J Sid]

Has the crack open up by moving apart with no difference in hight from one side to the other?

 

[Boom]

The tile is porcelain which will go on it, it’s a cement based screed. UFH has not been on yet. Will start from tomorrow

 

[J Sid]

Ufh needs to be commissioned before you start. So shouldn't be starting for a good few weeks yet.
If, and I suspect these cracks have vertical movement, the tile will cracking the same way as the screed and no amount of uncoupling membrane will stop this.

 

[Dan]

That crack needs investigating. If you have more like that, something has been done incorrectly I suspect.

Especially if you haven't ran the heating yet.

That could be shrinkage (too thick of a screed and dried too quick?) but could be wrong stuff used maybe too.

It's out of my league. But that's not a nice new fresh screed on top of UFH. Somethings gone wrong.

I wouldn't cover that up yet until you know why it has cracked so badly.

I've never seen a screed crack like that before and I've seen a fair few new screeds when UFH is involved. Usually get a little near where pipes come out the floor for radiators and things like that. But never a huge crack.

You got a photo of the floor from further away to put that picture into perspective? Maybe it's just a close up and doesn't look so bad when standing near it...?
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Sorry I missed this picture. That puts it into perspective.

Yeah that crack is huge. And to get splashes up the wall like that, perhaps was far too wet when put in. Not sure.

Over my head this is so I'll just watch and read the thread.

 

[Bond]

What is the total floor area and are there any construction joints in the screed/floor slab.

 

[Flintstone]

I've seen cracks like that often and it's not the end of the world. It's more than likely shrinkage. Commission your ufh correctly and see what the floor looks like after that. You can carry out a resin repair and reinforce with rebar, then fit uncoupling membrane and tile. Ditra and such like actually improve the performance of under floor heating as the channels in the mat help dissipate the heat evenly. Here is a repair I did on a crack last month

 

[J Sid]

Andy, I've seen cracks like this a few times and it's been vertical movement and only got worse when heating is on.

 

[Dan]

I wouldn't like to fit to a reinforced floor that's been retro reinforced.

Not that I even fit to any floor mind.

But if I did, I'd want another layer of something over it I think. Hide the cracks. Even if just from my own eyes lol
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I've seen cracks like that often and it's not the end of the world. It's more than likely shrinkage. Commission your ufh correctly and see what the floor looks like after that. You can carry out a resin repair and reinforce with rebar, then fit uncoupling membrane and tile. Ditra and such like actually improve the performance of under floor heating as the channels in the mat help dissipate the heat evenly. Here is a repair I did on a crack last month
View attachment 109635 View attachment 109636 View attachment 109637 View attachment 109638

That reminds me of a carpenters fix when they make tables out of split tree trunks and use a sort of >< shaped bit of wood to join the spits up. Table top ends up looking awesome and is stronger than without any crack in.
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Concrete and screed is @ATSDiamondTools and @Ajax123 all the way isn't it?

They available to say owt?

 

[Flintstone]

Id always lay an anti fracture mat if there was cracks visible in a new screed, like Julian says, providing it's not moving