Disaster levelling

[sambotc]

Hi all,

looking for advice on how to get around a disaster of a levelling job.

Basically we have cracked and slightly hollow sounding levelling compound in a low profile underfloor heating floor. It’s mostly solid as it’s bonded to the castellated panels, but areas sound hollow in places. I’ve ground the top layer off to give me some depth to play with, can’t go too far as I’ll hit the pipes.

I’m trying to avoid ripping it all out, pipework, panels etc as it would be a nightmare replacing it all.

Have thought of two options but looking for advice on whether either would likely work.

First is 4mm hardiebacker laid on top, presumable with some kind of flexible tile adhesive?

Second is to use a re-enforcement mat in/over/under the top and pour another levelling (Mapei 3240 or similar as it’s reenforced and flexible) over the top?

not sure if either of these would work or if anyone has any better ideas?

was hoping to LVT over the top

Any help much appreciated !

cheers!

 

[tell80]

From what I can see - the whole of the UFH has been installed too high in terms of your needed FFL?
Plus the SLC looks to be far too thin for purpose.

What is directly below the UFH panels? I ask because even if you "ripped it all out" for UFH replacement then whatever is below is presumably too high as well?

The 4mm hardibacker option will still raise you 7mm or 8mm or more depending on the LVT you use - this may work but could also cause knock-on problems with appliances and thresholds?
And, personally, I think that 4mm Hardibacker is too fragile for floor use - just me.

The second option is also a FFL height problem.

So, it would be the first option with the above doubts.
Hopefully, someone else will come along with a better solution for you?

 

[sambotc]

Hi,

thanks for the reply,

Levels aren’t an issue. the kitchen is new and has been installed with the raising of the floor taken into account for the plinths etc, but half of it isn’t installed anyway, as we wanted to get the floor done before installing end panels etc so plenty of scope to adjust as required.

basically, the floor issue was only noticed when the kitchen went in, as we had a temporary floor down over it all which was removed during the install of the kitchen and revealed all the problems. By that point we had a dining room full of new kitchen so we cracked on as best we could.

The more I look into the floor the more I realise how bad it may be, hence grinding back as much as poss to start over.

it’s a 1970s and I believe it may have had Marley floor tiles which, since reading on here after posting, I now realise this may have been the DPC?

if so, could this be part of the cause of the cracking?

Also, might be worth mentioning, the compound I was supplied wasn’t what I was expecting from the supplier (during lockdown, supply issues) and stunk of egg for weeks and weeks after laying. Could this indicate a bad batch?

As per the title, bit of a disaster!

cheers!

 

[sambotc]

P.S - sorry, I didn’t answer some of your other points.

the levelling is up to 18mm deep but variable as the castellated panels vary in height in places. They also have holes in them so the compound flows into certain parts of the panel, presumably to interlock it all together. Certainly seems to have worked as it’s generally solid, just hollow when tapping under some of the bigger gaps.

was +3mm over the top of the panel, I’ve probably ground 2mm of that back.

Cheers!

 

[tell80]

most SLC MFr's claim low smell FWIW.
SLC can be built up in layers but any depth over a few mm's often takes fibres or fillers to bulk it up.
Mfr's bag instructions explain.
The panels should all be on a level - no ups and downs.
The membrane (DPM) is irrelevant.

Well done for your DIY trying but given your kitchen floor seems to have been a no-go from day one, maybe call in a paid floorlayer for a heads up?

 

[sambotc]

Yeah it was definitely high smell, completely stunk the house out for weeks!!

I used Mapei 3240 in another room and as far as I can tell, no issues (although now carpeted I’ve peeled back a corner to check) and same panels, no problems at all, no cracking etc and there was no smell.

The stuff in question was a deep levelling product but I don’t recall it having fibres mentioned on the bag. Think it may have been ultra tile.

I’ve spoken to 1 floor layer already but they basically said they’d have to rip it up, which wasn’t exactly what I wanted to here if there’s another option… hence looking for a couple of other suggestions, in hope that there’s another way…

 

[crazydaze]

Was the screed used recommended by the UFH manufacturer?

How Clean was the UFH and channels before the primer (a seperate primer was used was'nt it?) and Screed were applied?

Was the heating off for 48 Hours before the primer and screed was laid?

How quickly was the heating turned on after installation of the screed? Was the heating turned on to room temperature straight away or was it turned up in small increments?

 

[sambotc]

Hi,

I spoke to the manufacturer of the panels and they said any deep leveller would be fine although they sold their own product (which wasn’t supplied due to stock)

Their instructions for install did not state a primer was required over the panels, so no, it was not primed…

heating was off for months before during on, then slowly increased in temp ( I’ve installed a lot of underfloor heating in the past)

As I say, the Mapei 3240 was poured over the same system in another room and appears to be fine so I don’t think it’s an issue with the method although happy to accept it is if I got it wrong!

 

[crazydaze]

We had 100m2 of Mapei Renovation blow over UFH a couple of months ago despite the primer (which lifted off the UFH).

Mapei put it down to everything (local conditions, temperature of the room, unclean floor surface etc) but insisted no issue with the product, solution? Clean off the existing blown areas as best possible without damaging the UFH, prime and re-apply.

We are still waiting on the outcome of reports as it's since been discovered the UFH has been installed over vinyl tiles !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[sambotc]

Ironically the 3240 is fine , it’s the other stuff that failed and stunk of egg, I was convinced it was dodgy but I’m no expert.

Is the reinforcement matt not a good idea then if I encapsulate it in the compound? I guess Mapei would be best placed to answer that.

I pulled out the thermal imaging camera today and can trace the pipework so I could possibly break out the hollow spots, but the cracking is pretty much all over, even though not all hollow sounding, and some of it is where the pipework is, so too risky to try chiselling out.

Appreciate everyone’s help

cheers!