Just looked at a job. Needs a liquid dpm and smoothing from 7 to 25 mm.very rough concrete like a garage floor. Just spoke to uzin tech, I can use l3 gold 1st, then 414 rapid dpm, 280 primer and top with l3. Only problem is the thickness of the screed (max 4mm unless you bulk it out with sand?). Ill have to do a few coats to get the height right.Anyone suggest another make/brand?Ideally want a rapid system. Thought about the Mapei 1kTurbo - do they do a screed you can use under a dpm? I don't really want to dpm straight over the rough base as I'll be going through loads of it and I'll have to apply it with a brush. Ardex DPM takes to long to set, I want something that I can do the whole lot in one go. I can't remember what products / recommendations were made on the freebie course. If there was a raid setting repair compound that I could use 1st, then DPM, I'd be laughing. The area is 28m2, needs 7mm at one end to 25mm at the other.
The 1k turbo does around 40 m2 a tin I think? Could you not get away with using the whole tin and charging for it or do you think you will need more? Mapie Renovation screed goes off pretty quick
whats the reason for needing a dpm? If the floor suffers from rising damp then there is not a surface dpm on the market sutible (well that can be applied under 50mm). Some manufactures say there is o.k, this is because the top layer of builders screed will shear so its not a product failer but a concrete floor failer. (get out clause for them) If the subfloor is wet due to new concrete then yes you can use Mapei Latex plan trade to 10mm, then use 1k turbo and then cap off with another layer at 10mm to get your levels correct.
There are 3 different heights to the floor. The original bit, then the 1st extension and finally a 2nd extension finished about 12 years ago. There is a sheet DPM under all of them but they are reading high on my Tramex. The walls have been removed and now the difference needs sorting out before the under floor heating is installed. It's a water system going in and the builder wants a belt and braces job done before the heating system is installed (going to be the pipes in the grey fibre boards, then ply then ceramics). He's going to gripfil battens to the screed to fix the ply to with the UFH running between them. I've just got to get the levels sorted before the UFH goes in.
Making it hard work mate. Can you not lay DPM sheet, insulation and then top of with 55mm fibre bonded concrete screed. Will sort moister and floor levels all in one go plus it will be the most economical way to run the heating system. Think you will end up with around the same sort of floor height. I dont like the sounds of 3 different concretes running into each other with high moister readings and then skimming plus surface dpm and throwing underfloor heating into the mix also. Will only take a slight movement of one the slabs and it will all fail.
I suggested that they go that route. The 2nd extension (last bit done 12 years ago) is not having UFH as that bits already to high, they are going to fit skirting heaters in that area. They may decide to go the new slab route after they get my quote. Works out I'll need 29 bags and that's just to get the levels between the original and the 1st extension area. The problem is that I have to leave 43mm above my finished level for the UFH system and ply to be at the same level as the original part of the house. Last one I did like this didn't need a dpm, just needed levelling, used 26 bags of 300 on that one.
i take it the builder does know that he has to install insulation and dpm sheet under anyway and that the pipes have to be covered in concrete. You cant just stick plywood over the top on batterns etc. You cant have any air gap at all between the pipes and the finished subfloor. He would be much better off not using plywood and just pouring fibre reinforced concrete straight over the pipes.
Cheers Matt. I'm going to call the makers today for advice and then the builder shortly after (probably telling him - as you say- that he needs to dig out more to allow for insulation, pipework and then minimum 50mm screed).
make sure you check out the minimum depth of screed over the top. They may want the screed to have a strength additive with fibres.
Spoke to makers of UFH system. They are happy for the 25mm board to be laid on the screed, pipes clipped in then 9mm ply on top finally topped off with ceramics. I've dug down and exposed part of the DPM sheet under the slab so I'm happy using trade plan, turbo then renovation screed. Will prim t be okay as primer on top of turbo? Thanks Pete
yes prim t is fine. Mix 1/1 with water. All the subfloor prep is below the underfloor heating? they are attaching the pipes to the top of your prep ?
Yep, all my prep work is below the UFH. The UFH pipes get clipped into the back board which sits on top of the prep work.
Been back today to screed the utility room. Looked at the area with the UFH. Could see loads of screws. Asked builder about them, he's only gone and used 100m screws through the ply, back board and into the conc. Also straight through the DPM. Told him he's now wasted his money and that there is now no warranty on the DPM. What a plonker Rodney.
