Nice one. You also should end up with a very quiet floor which isn't the case sometimes with underlay over a DPM.
Not meaning to hijack the thread guys, I'm going to lay a floor almost exactly the same as you have described next week. My only extra issue is that as it used to be 2 rooms one is about 3cm lower than the other. They are only small rooms though, 4m2 total. Could I put something like a thin insulation board down on the lower one before dpming and self leveling to deal with the really big depth change and the dpm will then sort out the minor imperfections?
Bring it on I'm glad you asked as got a similar room to do after! My initial plan was to pop screed off concrete. It's around 25mm at present. Self level floors to get level. Put the insulated 20mm tile boards on after. To get back up To similar ffl. Going to put shower tray down first then fit these boards around tray for super low profile shower entry
If you already have a dpm in place or have no signs of damp you wont need to use a liquid DPM. I have used XPPro (I think that's the name) boards before on a couple of occasions but only to prevent underfloor heating benefit being lost in a concrete slab. But the cost and hassle of using them outweighs any benefit really. I am not convinced about using them under a vinyl as I would be very concerned about the leveller cracking in a thin layer over insulation. I would just Setcrete primer the floor and then use Wickes Deep Base to bring this height up to whats required. You will need a lot though and will need a good system worked out. Use plasterers buckets ready filled with the right amount of water for a bag Maybe do it in two layers. But prime in between. As always. Don't forget click and collect through Topcashback for extra 4% back and to use the 10% trade discount.
Great tips mate thanks! Well the half that's higher has quarry tiles on and the lower was battoned with some underneath the battons. I could take up the quarry tiles but the few I took up are stuck like a mother and there's a capped ceramic toilet pipe going through it so the hassle of potentially cracking that is outweighed. And the walls have a damp course so I'm fairly certain the slab doesn't! If it's 30mm could I sbr slurry and just cement it or will it crack at 30mm even with SBR in it?
I cant advise on SBR and all that as its not something I know about. I would just automatically go down the Deep Base route.