Why You Should Commission A Heated Screed. - TilersForums.com

[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.

 

[J Sid]

Yes David, I am sure I would have tiled it. Not questioning your judgement or what you are planning to do.

What I am trying to see, is what guidelines are out there from TTA, uncoupling membrane manufacturers, BS, or any other body gives for when you turn up at a job to find cracks in a sand and cement screed, wether 1mm or 5mm.
It sounds like, from your replies and none replies form other notable trusted advisers that it is completely down to the tiler to make the call irrespective of there experience, wether that be 6 months or 40 years on the job.

I would in my "experience" tile most of these jobs, but the reason I ask is because I would like to know if the manufacturers, BS or TTA or the law are on our side if we tile these job in go faith using our judgment and they fail due to a bad screen. I have seen many screeds with wet ufh not crack. So is the presence of cracks proof of a incorrectly laid floor?

I did a floor the beginning of last year. Original floor was travertine, 50m2 on wet ufh with expansion joints in all the correct places, but full of hairline cracks.
I had to lift and replace with porcelain.
On lifting this floor I found no uncoupling membrane, possibly the only mistake that was made?
But as I lifted the floor I found that the screed was laid so badly, by this I mean a layer of screed was laid over the ufh pipes and trodden down and left to partly dry, lunch break or overnight, foot prints were as plan as day, with the top layer not bonded to this at all.

So this person doing the tiling would have looked at this job and thought, looks good, expansion joints, hairline cracks, good to tile. Yes no uncoupling membrane, but seeing the state of the floor and the debonding in the screed, how would he have faired with the uncoupling membrane supplier if one was used and failed? If he was a TTA member? Drummed out the club or backed in a court?

David just trying to have a debate and get the feelings of other members.
Having been away from the forum for a while, I have noticed that some of the notable members who, in the past would have jumped in with an opinion are not so vocal now they have been made advisers now

Sorry if I have hijacked your thread.

 

[Dave]

It's not hijacking at all , you have some very valid points .

I get TTA technical documents and these are all bs5385 related updates or full spec .

IMHO it is down to the tiler to make judgement and if the cracks did transfer then I don't think the TTA would back my or any other members decision if they thought an error was made but if it was followed to the T then I cannot see them arguing any error at all . ( I hope lol )...

 

[Dan]

I may well be wrong to be fair Julian! The products, tiles, adhesives and everything else that are available these days compared to when I tiled years ago is sometimes unbelievable.

Dave's the man when it comes to tiling.

 

[Just Rizzle]

did a job about 5 yrs ago were the ufh had cracked the screed really badly in several directions. we were laying a bespoke granite spoked curved granite elipse floor 7mtrs by 5 mtrs to give us Pease of mind we layed ditra mat on top of each other with leveller in between was back at job in feb for other work and floor looked as good as when we laid it

 

[J Sid]

Ray, you saying you laid Ditra then leveled, then Ditra, then tiled?
Interesting.....