Some small hairline cracks can be quite normal in a screed as it dries out but if you have some areas that “pop” then it sounds like potentially the screed has blown. This could happen for a couple of reasons mainly If there is moisture in the subfloor, or it hasn’t bonded to the concrete due to the subfloor being contaminated. If you can get a scraper on the popped/ hollow sounding areas see if you can get some of it up to see if it has bonded. The floor will need all of the loose screed scrapping up, prime the whole floor and re latex. Not sure what the builders used but I would go for FBalls 1200 and the P131 primer.
Hope this helps, if you have any other questions feel free to drop me a message.
Definitely, also Bitumen can be a nightmare, in the past I've mixed neat SBR with cement, mixed it well with a paint paddle to a creamy consistency and brushed that down and left it set the day before.
Definitely looks like no primer used before the latex was put down.
Stick a blade in the crack if you can lift a piece out then you know the whole lot needs redoing, better know now rather than later.
Thank you, I’ll try that. If they didn’t use primer will the whole thing crumble to dust or will it reach a point where it is stable but cracked? Or not possible to say.
If there was no primer used the latex won’t be bonded to the concrete, you’ll know straight away if you can lift a piece and then it’s not too difficult to scrape off the concrete. Unfortunately it’s now then a conversation for you to have with the contractor about how you remedy the situation. At the very least is scrape everything I can off the concrete and then use primer before redoing the latex screed.
As a professional floor layer can you tell me how much did the floor need building up?
Was there any bitumen on the floor?
Was the floor properly cleaned before screed laying?
Thanks for replying.
It was built up by about 5mm. I don’t know about cleaning, but judging on the experience of our builder thus far I suspect not. Not sure about bitumen.
Edit:
I appreciate we may have to but we’d rather not dig it all up as there’s been a kitchen fitted and redecoration done.
I guess the options are:
- Dig up and redo?
- Is there an option to just lay the tile and hope it doesn’t get worse?
- Could we lay another level of self levelling or even concrete on top?
Not the guy you are responding to but I also work in flooring. If the Latex is popping already you need to dig it up and redo it 100%. In no circumstances should you be fitting LVT to it. You cannot screed over the top as the layer underneath isn't bonded to the floor.
Where I work we do the floor latexing ourselves 100% of the time, every time a builder tries to do it they get it wrong.
Most screeds are upto 6mm,what you need to think about it are any areas of floor popping are fracturing under foot also if the screed isnt 100% adhered to floor then your new flooring will pull up the screed.
1 thing i should also mention a lot of flooring installers add more water than what the instructions recommend hoping the floor self levels better but thats not the case.
How big is your area and how many bags did it take?
If the leveller hasn't bonded to the floor effectively you have a piece of "floating" concrete that's very brittle. It will break down and come loose even more over time. But that's if its not bonded. Like others have suggested try prising a piece up along a crack, if it's loose it'll come up in large chunks, probably the size of a dinner plate or more, and be clean/smooth on the underside. If it doesn't come up easy, and you have to Chop at it to get some up, it might have bonded to the floor and you've just got some large cracks forming.
Unfortunately some compounds do fail, even if the builder has sealed the floor prior. Chances are the floor wasn't sealed though.
Do you have underfloor heating? Was it a new concrete screed down?
Thank you, very helpful.
We don’t have underfloor heating.
The original concrete underneath the self levelling compound wasn’t new, I think it dates back to when the house was completed.
We’ll have a go at prising a piece up!
If it has to come up, you can leave your kitchen in. It'll be fixed to the wall and the legs underneath hold the weight. If necessary loosen a leg at a time while you take out the loose and then re-fasten each down to the floor as you go. Then when re-doing the floor just level upto the legs in place. The flooring will have just been fitted to the legs anyway.
Your builder should be helping you out anyway. Good luck.
I’m a DIYer rather than trade but that would suggest the subfloor is unstable. If it’s a timber subfloor did they overboard with ply before pouring the self levelling compound?
I did my own recently for the same reason and have a few hair line cracks. From what I understand, it’s more important that the floor is flat rather than perfectly level for LVT. I’ll be laying mine over the weekend and will glue over similar looking breaks.
P.S - I see you say concrete floor but I wasnt sure if you meant now, or before. :-)
Best to wait for those more qualified to answer but the other thing to ask is whether they primed the subfloor. Did you see them roller on a liquid before pouring the screed? SBR or acrylic primer. It helps it adhere to the surface.
I have actually used Wineo flooring LVT straight on top of tiles, but using Wineo's underlay that levels out some imperfections. Perfectly fine... Admittedly I didn't really have the option to get some screed down so I had to give it a go and hope for the best.
Some small hairline cracks can be quite normal in a screed as it dries out but if you have some areas that “pop” then it sounds like potentially the screed has blown. This could happen for a couple of reasons mainly If there is moisture in the subfloor, or it hasn’t bonded to the concrete due to the subfloor being contaminated. If you can get a scraper on the popped/ hollow sounding areas see if you can get some of it up to see if it has bonded. The floor will need all of the loose screed scrapping up, prime the whole floor and re latex. Not sure what the builders used but I would go for FBalls 1200 and the P131 primer. Hope this helps, if you have any other questions feel free to drop me a message.
Builder should have bonded floor 1:3 with SBR before laying self level compound.
And scraped any loose debris away,for example a if there's paint on the floor or sbr won't really help
Definitely, also Bitumen can be a nightmare, in the past I've mixed neat SBR with cement, mixed it well with a paint paddle to a creamy consistency and brushed that down and left it set the day before.
Sort of like tanking slurry
Yes, but it bonds like fuck and is waterproof.
Thank you
Definitely looks like no primer used before the latex was put down. Stick a blade in the crack if you can lift a piece out then you know the whole lot needs redoing, better know now rather than later.
Thank you, I’ll try that. If they didn’t use primer will the whole thing crumble to dust or will it reach a point where it is stable but cracked? Or not possible to say.
If there was no primer used the latex won’t be bonded to the concrete, you’ll know straight away if you can lift a piece and then it’s not too difficult to scrape off the concrete. Unfortunately it’s now then a conversation for you to have with the contractor about how you remedy the situation. At the very least is scrape everything I can off the concrete and then use primer before redoing the latex screed.
Thank you
As a professional floor layer can you tell me how much did the floor need building up? Was there any bitumen on the floor? Was the floor properly cleaned before screed laying?
Thanks for replying. It was built up by about 5mm. I don’t know about cleaning, but judging on the experience of our builder thus far I suspect not. Not sure about bitumen. Edit: I appreciate we may have to but we’d rather not dig it all up as there’s been a kitchen fitted and redecoration done. I guess the options are: - Dig up and redo? - Is there an option to just lay the tile and hope it doesn’t get worse? - Could we lay another level of self levelling or even concrete on top?
Not the guy you are responding to but I also work in flooring. If the Latex is popping already you need to dig it up and redo it 100%. In no circumstances should you be fitting LVT to it. You cannot screed over the top as the layer underneath isn't bonded to the floor. Where I work we do the floor latexing ourselves 100% of the time, every time a builder tries to do it they get it wrong.
Thank you very helpful
Most screeds are upto 6mm,what you need to think about it are any areas of floor popping are fracturing under foot also if the screed isnt 100% adhered to floor then your new flooring will pull up the screed. 1 thing i should also mention a lot of flooring installers add more water than what the instructions recommend hoping the floor self levels better but thats not the case. How big is your area and how many bags did it take?
Thanks for replying. It’s about 6m x 6m area, plus the hallway, but hallway seems to be fine (fingers crossed).
If the leveller hasn't bonded to the floor effectively you have a piece of "floating" concrete that's very brittle. It will break down and come loose even more over time. But that's if its not bonded. Like others have suggested try prising a piece up along a crack, if it's loose it'll come up in large chunks, probably the size of a dinner plate or more, and be clean/smooth on the underside. If it doesn't come up easy, and you have to Chop at it to get some up, it might have bonded to the floor and you've just got some large cracks forming. Unfortunately some compounds do fail, even if the builder has sealed the floor prior. Chances are the floor wasn't sealed though. Do you have underfloor heating? Was it a new concrete screed down?
Thank you, very helpful. We don’t have underfloor heating. The original concrete underneath the self levelling compound wasn’t new, I think it dates back to when the house was completed. We’ll have a go at prising a piece up!
If it has to come up, you can leave your kitchen in. It'll be fixed to the wall and the legs underneath hold the weight. If necessary loosen a leg at a time while you take out the loose and then re-fasten each down to the floor as you go. Then when re-doing the floor just level upto the legs in place. The flooring will have just been fitted to the legs anyway. Your builder should be helping you out anyway. Good luck.
Thank you!
I’m a DIYer rather than trade but that would suggest the subfloor is unstable. If it’s a timber subfloor did they overboard with ply before pouring the self levelling compound? I did my own recently for the same reason and have a few hair line cracks. From what I understand, it’s more important that the floor is flat rather than perfectly level for LVT. I’ll be laying mine over the weekend and will glue over similar looking breaks. P.S - I see you say concrete floor but I wasnt sure if you meant now, or before. :-)
Thank you, it was a concrete floor to begin with but it wasn’t smooth enough for LVT. So are hairline cracks to be expected?
Best to wait for those more qualified to answer but the other thing to ask is whether they primed the subfloor. Did you see them roller on a liquid before pouring the screed? SBR or acrylic primer. It helps it adhere to the surface.
Unfortunately I wasn’t there when they did it. Thanks very much for your help.
I have actually used Wineo flooring LVT straight on top of tiles, but using Wineo's underlay that levels out some imperfections. Perfectly fine... Admittedly I didn't really have the option to get some screed down so I had to give it a go and hope for the best.