readiescards Posted January 23, 2017 Share Posted January 23, 2017 Do I need to be concerned about 3-5mm height difference between the blocks and beams in my sub floor? The plan is for a DP membrane (not sure of thickness), 200mm of PIR foam, ufh in 50-60mm concrete screed, Luxury vinyl tiles. Options I see are: Do nothing 1200 gauge DPM Dry sand Leveling compound Other? Thanks Link to comment Share on other sites More sharing options...
CC45 Posted January 23, 2017 Share Posted January 23, 2017 Hi, We started off with what you've got. Dpm then 2 layers of insulation - 1st at 90deg to the beams. We used 75mm celotex - this 'crushes' slightly - joints taped. Next 150mm celotex at 90deg to the first layer - if they rock (celotex is far from 'flat' - this surprised me) then use some sand to bed them onto. Take your time and you will achieve a level floor that doesnt rock. The screed will take out any imperfections. We put another sheet down under the ufh pipe and don't skimp on the clips - you dont want them lifting while the screed is going down (screeders said this wasnt unheard of). Remember to grout the B&B (ours wasnt done very well so I redid it). Dont be tempted to turn the celotex upside down - the underside foil isnt bonded on very well. Hope that helps. 1 Link to comment Share on other sites More sharing options...
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