We're preparing a subfloor to take a new floor in our utility. The intention was to put electric underfloor heating mat and then tile with matching tiles to the kitchen. The old (engineered wood) floor had been laid over a plastic sheet over the old concrete subfloor. It's clear that previously there was some parquet flooring glued to the floor. There's bitumen left on the concrete in most places. There is evidence of some damp under the original plastic sheet. Given the age of that bit of the house there ought to be a proper DPM underneath. There's certainly DPM visible in the external walls. There is some evidence of damp in the external walls, so these are likely related. So I'm after advice on how to prep the floor. Original intention was to lay ProWarm tile backer boards down with tile adhesive, then heating mat, latex self levelling then tiles. I'm unsure how to proceed now. It feels like gluing the tile backer boards directly down onto the floor as it is is likely to be a bad idea. It doesn't look like the floor is all that level, so it's probably going to need levelling before the tile back boards anyhow. From what I read, sounds like there needs to be some "Ardex NA", plus "Ardex DPM1C"? What's the build up there? Who would I get to do that kind of thing? Is that a specialist kind of a job? Do we need to scrape back to the concrete slab first? Is a tile scraper machine the best thing for that? Thanks.
I can see I'd need to remove anything loose etc, maybe any remains of actual wood. The Ardex NA says it can be laid over bitumen adhesive residue, so on the face of it I wouldn't need to go back to pristine concrete and remove every last trace of the previous covering? I'm thinking get rid of anything loose, the worst of the what's there, Ardex NA to level, Ardex dpm1c to ensure functioning DPC, then second thin coat of Ardex NA to protect DPC and provide surface for the tile backing boards (Ardex seem to recommend sandwiching the dpm1c)?
That's good to know. The current floor is surprisingly unlevel. There's a 30mm difference from one corner to the opposite corner. Ardex NA says you can mix with their own "aggregate" (is this special in any way?) to bulk it out and increase the coverage and basically make it more economic for thicker pours if I understand it. I was planning to do two pours of NA. One bulked out with aggregate to bring the level most of the way up in the low parts, let it dry, then another thinner layer over the entire floor. Aim would be for the second layer to be in the 5 mm thick range. That would then give me a hopefully level floor. Sound sensible?
