Hi, New to the forum. Have read many threads trying to gather info, but got to the point where I just need advice. I’m in the process of a new build. Sub floor (whole ground floor) is anhydrite with UFH, over insulation and DPM. Intended final flooring is Karndean Art Select. Screed has been down for 3 months, heated with windows regularly opened for 2 months. Prep work has been: Feather edge to sort some edge issues Primer Epoxy DPM 3mm Latex screed Issues: Cracking and debonding of latex screed in several isolated locations Bobbling (like bubbles, but actual raised bumps) in patches Fitters don't know why either has happened. Have commented on potential bad screed batch, or UFH (although off days before, during and days after as advised) Debonding has been fixed by chipping away, re DPM'd and filled with feather edge. It's a large area, so has not ben fully checked for debonding anywhere else. Bobbling has been sanded In the meantime, I've done my own research and spoken to the manufacturers (each layer is a different manufacturer) and have basically established: Potential problems of cement over anhydrite Potential problems of DPM over anhydrite The actual DPM product is not recommended for heated concrete (in sales brochure) Primer should be used on DPM before latex screes (in application guide) All the manufacturers said the floor should have been tested for moisture. I'm fairly sure it wasn't. All said the mix of manufacturers wasn't helpful in the event of a problem. Also I don't think the laitance was sanded before primer (certainly not machine sanded). Slightly unrelated, but the latex screed is 'low' - I discussed this when the UFH screed was poured. We have a stupidly small front door threshold so discussed pouring short as was told (by the fitters) the finished floor level could be adjusted during the prep work as they would be more controlled. The floor is also uneven - won't meet SR1 in places (as advised by Karndean technical). Both level/flatness is now being blamed on subfloor. I have no problem with extra costs due to subfloor screed issues, other than not establishing that before £1000s of prep work. Fitter saw screed a moth after pouring. Priming again and applying another full latex screed is considerably more expensive than laying thicker first time round and levelling out. The main concerns are being dismissed as 'manufacturers covering their own backs'. I find it hard to be this dismissive considering we have seen two separate issues and the advice given. I have spoken to the fitters and am being offered to either 'trust them' and we'll have a great floor, or have them remove everything and we start again with someone else. I am conscious of the work/costs involved so far, the work involved undoing it, the knock on effect on my schedule/trades, but the fact that we have seen issues and the advise of the techs against what's been done, tells me to start again. I don't know the worst case scenarios, but I do know someone who has had to completely demolish and rebuild a two story extension due to bad concrete mix in foundations. The cost of repairing a failed subfloor (removal of kitchen, furniture, skirting etc. temporary accommodation, replacement products) would be astronomical, and I would question the liability insurance response if the use of products were against the manufacturers advise. Am I being over cautious? Could the floor fail further and what would be the effect? What's involved in removing it back to the UFH screed?
Wrong prep Did they or anyone grind the Laitance off ? If not anything put on it will blow Especially anything cement based Got any pics ? Sounds like your installers really don’t have a clue at all
I'm not aware of anybody grinding the laitance off. May have had some hand sanding but big area and weren't here long. Here's some pictures. 'Bobbles' in the latex and different texture colours Patch up of debonded area in two areas Further cracks we found this morning
Everything that’s been done needs to be removed It’s all completely done wrong There’s no fixing it It’s already failed Then the top of the Anhydrite needs to be completely grinded ( not sanded) off with a grinding machine until the aggregate is visible Then turn on the UFH to dry it out (Prepare for a lot of condensation) It will take about two weeks to dry Then you can start again properly
I had a feeling that was going to be the conclusion. How much of a job is it getting it all up? Do I need to protect windows etc.?
Will we still have moisture? The anhydrite screed was 3 months ago with 2 months of UFH on. The feather/primer/DPM/latex was last week.
More than likely The UFH will cook the Laitance and form a rock hard crust sealing the top I’ve had to grind cooked laitence a few times when it’s been left to long and the moisture that came out afterwards was unreal You’d think it had been raining indoors
The laitence retains the moisture, so the screed won’t dry properly. Remove the laitence, I normally sand it, as recommended by manufacturers, I use ERH 43 and a hard disc, you’ll know when you’ve removed it the aggregate will start to become visible and the colour of the screed changes slightly. I’d check the mc, then run the ufh on low for a couple of weeks, check again, for an accurate mc check, the ufh needs to be off so the Screed can reach equilibrium again. Normally you can’t use a liquid DPM over an anhydrite containing UFH.
That looks like a builder has slapped down some crap screed, nothing close to what a professional flooring installer should be doing. Sent from my iPhone using Tapatalk
As above ALL wrong, sack your floorlayer and get somebody in who k ow what they are doing, there are no shortcuts with anhydrite non what so ever
Have someone coming tomorrow to look at it and hopefully get some idea of what’s involved stripping it off.
On the basis it needs to come up, what’s the cost? Anyone want to give me a rough price for removal? Approx 130m2 in Sheffield. And also any costs for grinding the laitance?
What a nightmare! The company installing just don’t know how to deal with your subfloor. They will be trying to patch it and hope for the best but it may always have problems unless it’s redone properly Sent from my iPhone using Tapatalk
Bigger than your standard house aswell. Taking all that up is going to be messy, think you better book that hotel after all....infact I'd book a holiday.
yup, completely wrong prep wrong materials wrong system (dpm etc) uzin do a complete system, as does eurocol (tho I havnt used it myself) get a firm in who know how to work with this stuff, simple as that, as they have been caught completely unawares by the looks of it rip the lot up, that's a painful option I grant you But better to go back to bare bones and get it right, than patch it and have nightmares further down the line
Looks like it’s going to be pulled up. Very frustrating - the knock on is I have had to put staircase, joinery, kitchen etc. on hold, which delays eventual moving in date.
