Why You Should Commission A Heated Screed.

[Dave]

All screed types with wet ufh should commissioned as we know but a sand cement mix screed is more prone to cracking when heat is introduced and further cures over the next few months ..

This floor is an example of what can happen once heat is applied , it was fine when I measured the job and I advised crack mat and customer looked like they do lol... But when I came back they knew my advice was correct at the time of quoting..

Always insist the floor is commissioned....

 

[J Sid]

Why are we only one of a few European countries to required the heating to commissioned before tiling?

 

[Dave]

I think the pic is self explanatory ?

 

[Dave]

If I tiled that before commissioning then what do you think would have happened and the screed was heated slowly.

 

[J Sid]

So why does this happen in other countries?
Are our screeders that poor?
Are our screeding products that bad?
The correct processes aren't followed?

What your pic shows, I would suggest is a very badly laid screed. I have seen the same many times, as we all have.

I have seen that happen when the floor screed / builder decides to have a lunch break half way though laying the floor.
Also I have seen this happen when the screed is to thin, covering the ufh pipes by under 10mm.

I maintain that a screed laid properly with the correct products and the correct processes would not do that.

So I suggest the reason we should commission ufh is to fine out how well the screedrrs have done there job.

 

[Dave]

I agree 100% but we are mere tilers covering our arses... Due to what others do before we are even consulted .

What we have is the first trade doing there so called stuff , get paid and moves on , then the tiler comes and does not know how thick the screed is or anything , simply the kinda word of what they remember Went down will do.

 

[J Sid]

So, if we turn up to do a floor with wet ufh and find it has been commissioned, we are told as per instructions / recommendations, and find the screed has developed these large cracks, what should we do?
Investigation further?
What does the TTA say, you are a member?
Condemn the screed? If no, at what point would you consider this course of action?

 

[Dan]

I'd assume the customer has been told porkies or is telling porkies if the screed is meant to be perfect and has developed cracks. Either that or a bad mix maybe.

Not much you can do but prevent the crack going through to the tiles.

 

[J Sid]

Dan, I believe you are wrong when you say "not much we can do"
We turn up at a job and see a screed with cracks in it, I am asking at what point should the tiler be asking themselves:
Is this floor safe to fix onto?
Yes, we have uncoupling membranes designed to deal with problematic substrates, but when does problematic be condemnable?
What guidelines are out there for us to follow? Or do we just follow our gut instinct, I hope not!

If we turned up and found a crack, as in David's photo, running across a door threshold we would not think twice and put an expansion joint in, so why not put one where we see it in the photo?
I must say Dan, I am surprised by the silent, perhaps the TTA members, more knowledgeable and trusted advisers are formulating there answers, or just having the bank holiday weekend off.

 

[Dave]

The crack isn't in a straight line , so inserting a movement joint will do nothing .. TTA technical document tiling to heated screeds does advise the use of an anti crack mat , the screed is sound and not hollow or loose , it is a stress related crack .

So in your opinion Julian , would you not have tiled it..

Sand cement screeds can crack and the one above is only a mm wide , so nothing major IMHO.