We're having UFH fitted to a new extension. It's part of a bigger project, which will include new plumbing to the remainder of the house too, so a huge project. We have a family friend who's a plumber, but we avoided asking him initially, as he'd been a bit unreliable in the past (not his work, just offering to quote for stuff, then never getting back to us), but eventually did after showing about 5 plumbers around and all of them rejecting the work. Family friend agreed to do it and gave us a really good friends and family day rate too.
However, he (or possibly his employees, I'm not sure) has now laid the UFH and it's wrong. The plastic membrane is meant to go on top of the insulation, then the pipes, then liquid screed on top. They've laid the membrane on top of the pipes. Why, I've no idea?! I get the impression they've misinterpreted the manufacturer instructions perhaps. This means the screed won't run properly around the pipes, so it won't heat efficiently and also, the screed would effectively be resting on air around the pipes and will likely crack. We were meant to get the screed done yesterday, but the screeders have refused in its current state.
A few days on (phone calls with manufacturer and his screeder, by the sounds of it), plumber has now realised it's wrong (although trying to blame manufacturer). He's said the best solution is to take up the membrane and use it only on the edges, then spray a PVA glue and water mix over the remaining insulation and pipes in the middle. Plastic membrane is designed to stop the screed seeping out I think. So, does anyone know much about UFH installation? Is this a valid alternative method and will it work?
Ideally we'd get him to take it all up and do it again, but we need to keep him on side, given he's the only plumber willing to do the rest of the house too!