Hi All, After some advice, we’ve had someone screed our floor on top of our newly fitted wet UFH heating system. Long story short it has ‘blown’ in multiple places suspected to be down to the fact that the primer either wasn’t spread properly or it was still wet when the screed was applied. And so there has been a chemical reaction between the screed and aluminium on the UFH boards. Not only this but they also didn’t lay it thick enough, should have been 5-7mm thick but was laid at 2-3mm thick max. basically what I want to know is based on the state of it, pictures attached is our only option to pull it all up and start again? Thanks
No the heating was never turned on (boiler was capped off). top is red with primer as originally we were told by the flooring supplier that the solution to the fact that it had blown was to use another type of screed and go over the top. it was only when my builder popped by the house he alerted us to the fact he didn’t think it was right so we put the breaks on it and are now trying to get answers before we proceed.
That’s not deep enough, should be fully primed and then have a min 10mm of a flexible compound over it, what’s been put over it ? I assume it’s commissioned ?
Yes we know for sure it’s not deep enough as the guy who laid it only used half the amount of screed that was provided to him, the amount provided was the exact amount needed for the number of boards -5% wastage. the product used was instarmac ultratile prolevel two. basically we believe we’ve got 2 issues. 1. There’s been a chemical reaction between the screed and the aluminium of the UFH boards due to either the primer not being dry enough or being patchy on the boards. 2. not enough screed used, my plumber said the floorer needed to lay it 5-7mm thick (quoted from UFH board manufacturer) and he’s layed it at about 2-3mm max (half the amount of screed left) . we now just want to know if we need to try and carefully take all the screed up and start again or whether we can put another layer of screed over the top? thanks again everyone for your feedback/time it’s much appreciate!
No point putting another screed on top, it'll be as good as what is underneath it....and that's loose! Needs taking up and doing properly
It may be too thin but weve done coat systems Without the first coat blowing. I wouldnt trust instarmac. Its never worked properly when I’ve used it. Whats beneath the ifh overlay panels and how were they secured?
I agree with Merit, I've used the instarmac twice because it was spec'd by the ufh (water pipe) manufacturer for warranties and it has gone down ok but needed to be alot thicker. I was told 10mm minimum but it probably ended up around 12-14mm. I find the mixes inconsistent therefore anytime I get the chance to use Mapei renovation I do because I've done stacks without 1 issue. Needs taking back up and doing again properly and this time prime the hell out of it and drop minimum 10mm layer down. How your floorlayer thought by going over a blown floor with another layer he'd get away with it is daft. Is he really capable of the job???
Hi all, thanks for the replies, we’ve told the floor layer that it all needs taking up and replacing at his expense, interestingly the manufacturer of our UFH board is who specified 5-7mm thick. sounds like you’re all recommending at least 10mm? We’ve got a finishing layer of screed going on top (1-2mm) and then having Kardean LVT. May specify he needs to lay 10mm of the first screed if you all believe this is the correct thing to do ? Thanks again!
Get your guy to lay minimum 10mm even if it's 2 layers of 5mm (making sure he primes between layers) and you'll be fine. Why these manufacturers spec 5mm is ridiculous in my opinion. Out of all the wet ufh suppliers I've dealt with only 1 specs 5mm but I still do 10mm minimum. If your guy does do the 2 layer option then leave 24hrs between the 1st & 2nd coat. Make sure he uses the correct primer and a decent fibre based compound.
They’ve dropped the depth to keep the cost of the system down i would guess. Most customers are probably shocked when they find out how much levelling compound they need to buy for a 10mm coat. I still can see a thin coat being the issue unless the boards are not fixed correctly
The depth will vary depending on weather a wet ufh system is within a xps routed board, aluminium topped board, cement faced board or gypsum routed board, there’s a few out there that can do 5-6mm but for me 10mm should be a minimum, should be a flexible compound
