Digger1 Posted June 21, 2022 Share Posted June 21, 2022 Question on the build up on top of an existing slab. I was thinking of the following construction: Existing Slab DMP sheet PIR Insulation 100mm DMP sheet UFH Liquid screed Any opinion appreciated. Link to comment Share on other sites More sharing options...
Temp Posted June 21, 2022 Share Posted June 21, 2022 Can you afford more insulation? Say 120-150 mm. If tiling beware that extra prep maybe required for Anhydrite Liquid screeds. They can form a weak layer/skin on top called laitance that is harder to bond to. This may have to be sanded off. Link to comment Share on other sites More sharing options...
jayc89 Posted June 21, 2022 Share Posted June 21, 2022 Looks sensible to me. Rather than focusing on insulation depth, my advice would be to focus on estimated u-values as that can alter dramatically based on your PA (perimeter area) ratio. Link to comment Share on other sites More sharing options...
Digger1 Posted June 22, 2022 Author Share Posted June 22, 2022 Would a liquid DPM be better than a sheet on the existing slab? The existing slab is uneven in places, i assume you can put a layer of sand/cement under the insulation so create a flat surface and compact it, just as you would on an oversight? Link to comment Share on other sites More sharing options...
Mr Punter Posted June 22, 2022 Share Posted June 22, 2022 Polythene DPM is probably cheaper and it is clean and easy to install. If the slab is not flat you could use some sand to level it before you put down the DPM. Link to comment Share on other sites More sharing options...
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