New cement based screed cracked

[ToughButterCup]

30 minutes ago, Jilly said:

...

episiotomy-like.

...

 

Now that @Jilly, thats below the belt.

Having watched a couple, the only peron I would wish such a procedure on  is Donald Trump. Follwed by a prolapse and an anal  fistula or two

[SteamyTea]

1 hour ago, Jilly said:

As I don't have an angle grinder,

Buy a small, cheap one.

1 hour ago, Jilly said:

and there UFH pipes under the doorway

Go carefully.

[saveasteading]

Benefits Of Specifying Cemfloor Liquid Concrete Screed

• No shrinkage, cracking, or curling.

 

This quote is from the Cemfloor website.

 

Therefore it seems that there should not be any cracking, and that this has been laid wrongly.

I have not used this screed but responsible for thousands of m2 of concrete.

With concrete, (which always shrinks) uncontrolled cracking is mostly down to 3 things.

 

1. too much water in the mix, for the ease of the workers.

2. absence of crack control 

3. reflective cracking from a slab beneath, or some other weakness.

 

1. Is the likeliest in your case as it has happened so quickly and very wide cracks in the time.

2. Almost certainly, and would have allowed the cracks but in a more controlled fashion.

3. I don't think applies as you have poured onto PIR (?)

 

As Nod and others say, this could come through any tiling /vinyl flooring you may install.

 

I predict that your installer will say it is

a) normal: refer to Cemfloor statement above. I'm surprised at other comments that this is normal. But normal is not the same as right.

b) not  a problem. In which case why is it a selling point with Cemfloor.

c) easily remedied by filling with some cementitious stuff. I don't think so: other cracks may come later too. It is impossible to fill a rough crack unless it is wider, and they will likely just smear some stuff on the top.

(Fill should mean to the whole depth. The cracks are extremely rough and jagged and liquid or paste will not pass through.)

 

At the door, this cracking could almost have been guaranteed. The screed shrinks away from all the walls and of course fails across this weak line.

 

The UFH pipes will be helping somewhat as a light weight reinforcing mesh, so it would probably have been worse without it.

[SteamyTea]

48 minutes ago, ToughButterCup said:

Having watched a couple, the only peron I would wish such a procedure on  is Donald Trump

Whose? 

Not sure if it is possible to do one on Trump, to the best of my knowledge he only acts like a vagina.

Still, will make him a silent, irritating, little fart.

Edited December 22, 2021 by SteamyTea

[saveasteading]

1 hour ago, Jilly said:

I don't have an angle grinder,

Your contractor, who is responsible for this, will have one, but what are you thinking of doing with it?

[epsilonGreedy]

1 minute ago, saveasteading said:

Your contractor, who is responsible for this, will have one, but what are you thinking of doing with it?

 

 

I assume the intention is to cut through the crust of screed smeared over the separator shim already embedded at the door threshold. My guess is that if there is going to be movement a crack will open at the shim despite the few mm of screed over it.

 

Maybe the objective is to provide a visual guide for later tiling.

[Russell griffiths]

 

movement joint at every door, purposely set off centre to line up with under the door, so when tiled the movement trim is hidden under the door. 

This one has a sliding door face fitted to that wall. 

[wozza]

We had Cemfloor.

 

We fitted thin blue foam strips (UFH Stuff) across all doorways - no cracks apart from where it covered the foam.

We were told by the contractor that we may get a cracks at two certain points (he had seen some similar floors crack and others not) and that it was up to us if we fitted foam, we didn`t fit foam and it cracked. He said it was normal and not to worry.

[BobS]

After my original post I contacted Cemfloor directly with photos. They told me these cracks are not normal for their product and indicate either a problem with the installation or material.

 

However, they also asked some questions about the company who poured this and it eventually emerged that it was not Cemfloor Therm, as we were sold, but a different product called Longfloor. At no point was this product discussed and we were repeatedly told this was Cemfloor up until the point Cemfloor themselves confirmed they do not supply the company.

 

The cracks have got worse since my original post and curled. We have not even used the UFH yet.

 

Our builder is now claiming Longfloor is just a different brand name of the same product and these cracks are normal. Clearly it is not the same as it has cracked badly so I wanted to correct my post saying this is Cemfloor as it potentially damages their reputation unfairly.

[saveasteading]

Well done for confirming whose product it isn't. 

I looked up Longfloor and they state that shrinkage is 

Drying Shrinkage - <500µm/m pH - ≥10

If I have my figures right that is 1/2mm per m or 1:2000

 

If your room is 4m long then a crack would be 2mm.

 

Cemfloor are the same, so their statement of No Cracking is incorrect.

 

We are back to: it should have had a crack inducer/former across the doorway.

 

 

 

[Dave Jones]

looks a really bad job, big lumps all over and not flat.

 

As your not going to rip it all out negotiate some price reduction before they get on there horses and rise off.

[saveasteading]

Curling you mentioned. 

That is a worry as to curl it has to bend up off the underlying surface, so will crack when it drops back to pace when loaded.

The 

 

If I had done this bad job to my own house I would let it cure completely, then stamp or thump all over it to make it crack, then rub it flat with a stone (a brick even) and fill the cracks cosmetically. It wouldn't  be right but I'd be living with a risk of my own creation.

 

BUT I wouldn't accept that from a supposed specialist contractor. 

Discussion  would start as 'break it all out and do it properly'. It would probably end up as 'no more money, just go' on the assumption that thy haven't been paid.

 

As you have UFH pipes in there it is very much more complicated.   I winder what stresses are occurring in the pipes as the screed shrinks and curls.

The pipes are working as a sort of reinforcement so the cracks may have been much wider (and more numerous) without it.

 

If they are your general builder and you want to keep them, then only you can decide.

 

 

 

[Adsibob]

16 hours ago, saveasteading said:

Cemfloor are the same, so their statement of No Cracking is incorrect.

This means that your builder might not actually have erred by using the wrong product. Unless there is some objective inferiority in the product that can be pointed to. There could still be issues with the installation method though. Did he run the UFH heating too soon or two high after the pour?

[BobS]

11 minutes ago, Adsibob said:

This means that your builder might not actually have erred by using the wrong product. Unless there is some objective inferiority in the product that can be pointed to. There could still be issues with the installation method though. Did he run the UFH heating too soon or two high after the pour?

Longfloor has an integral curing agent to stop cracking rather than one which is sprayed on later. As far as I can tell it is relatively new on the market so unsure how tried and tested it is.

 

The fact Cemfloor said the cracks indicate a problem with the installation or material when they thought it was their own product makes it difficult to accept this as an equivelent.

 

The UFH had not been turned on at this point. We have a temporary willis heater connected up which is warming it very slowly but yet to reach 20 degrees.

 

As @saveasteading says, crack inducers would seem to be the key. It makes no sense to me that they didn't use them.

[Gordo]

On 19/12/2021 at 15:29, dpmiller said:

Our screeders put a submerged foam joint at every doorway.

Good practice there. I see this all time at doors. Regular cement screeds should be poured in bays of 14m2 (I think that's the figure maybe its 36m2) with control joints to induce cracks where you'd prefer or saw tracked a couple of days after for same effect.

Edited January 6, 2022 by Gordo

[Adsibob]

12 minutes ago, BobS said:

Longfloor has an integral curing agent to stop cracking rather than one which is sprayed on later. As far as I can tell it is relatively new on the market so unsure how tried and tested it is.

 

The fact Cemfloor said the cracks indicate a problem with the installation or material when they thought it was their own product makes it difficult to accept this as an equivelent.

 

The UFH had not been turned on at this point. We have a temporary willis heater connected up which is warming it very slowly but yet to reach 20 degrees.

 

As @saveasteading says, crack inducers would seem to be the key. It makes no sense to me that they didn't use them.

Well if it is not as well established as the product you thought you were paying for, then this is really poor on your contractor's behalf and he should be rectifying it for free and apologising profusely.
I really feel for you, as it seems your contractor has cut corners without your permission. Your remedy would be for him to, test the UFH pipes are okay, fix if not, make good the cracks and leave the screed in the condition you expected it in. What is your floor finish on top of the screed, as if all the cracks are going to be hidden, it should be quite straightforward for him to patch it up. Or are you concerned about the structure of the screed and the integrity of the UFH pipes? I think it's unlikely they will have been damaged but I'm no expert. If there is any problem with the pipes, then  that is going to be harder to fix, but still fixable.

[nod]

On 22/12/2021 at 11:05, Jilly said:

Our screed has smudged over the doorway cracks, which I now know were put in deliberately, episiotomy-like. As I don't have an angle grinder, and there UFH pipes under the doorway, does anyone have any suggestions? Maybe just walk on them to crack them before the tiles go down?! And will use coupling membrane. 

I wouldn’t worry Your tiler will put a movement joint in each doorway Which will allow the screed to move without effecting the floor tiles 

[BobS]

1 hour ago, Adsibob said:

Or are you concerned about the structure of the screed and the integrity of the UFH pipes? I think it's unlikely they will have been damaged but I'm no expert. If there is any problem with the pipes, then  that is going to be harder to fix, but still fixable.

Yes, more concerned these cracks will grow in the future, especially once we put the heating on. It seems like the oval part in the centre of the doorway is now fully seperated from the rest but probably held in place by the UFH for now.

 

We are planning to put Karndean down so thinking the tiles could start to seperate and lift over time.

[markharro]

On 06/01/2022 at 17:59, Gordo said:

or saw tracked a couple of days after for same effect.

 

I have a connected question. We will be laying an insulated slab intending to use the powerfloated concrete as our final floor finish. What is best practise on cutting expansion joints? We will have UFH 50mm under the slab so that is one issue and of course no rooms/doorways.

[saveasteading]

This is a skilled job, so your contractor should advise. However they don't always fully understand, so you are right to ask.

It depends on concrete thickness and mesh selection.

I don't have the book to hand.

It will  need something between 4 and 6m centres for cuts.