Brian in Dorset

Thanks for the advice Russell, much appreciated. Leaning towards screed again. Dont want the TV to be jumping around.

I am about to install a celotex + anhydrite screed floor above the existing concrete floor and rear extension (B and B) I want radiators rather than UFH and if possible use 15mm PEX so no joints underfloor. I will have 22mm from unvented tank on first floor landing to manifold in the hall. Pipes to run in 15mm PEX to each room. I am looking for the best way to run the PEX in the floor. I have a few ideas such as trunking/conduit in the insulation coming up through the screed by the radiators. Alternative is to run in the screed a bit like UFH pipes with clips. Last option i have come up with is to channel into the original concrete floor and run PEX in trunking under insulation. Anyone any ideas and/or experience of such things and can offer any other ideas and/or hints and tips. Thanks Brian

Following 3m ground floor extension and loft conversion i am looking to raise the height of existing concrete ground floor. (floorplan attached). There are currently smallish differences in floor height between rooms and hall and a little bit of "out of level". I have been looking at an increase of about 100-120mm and we increased downstairs wall height by a whole block. I am considering 50mm celotex and 50mm flowing screed which will allow me a bit of tolerance with celotex levels etc. I am now thinking about 80mm celotex and 22mm P5 boards. is it possible for a competent DIYer to get a level enough surface on top of celotex to fit the boards and for the whole thing to be acceptable result? Is there a foolproof way to sort out differences of level (maybe 3mm over metre) and level (maybe 0-15mm) between rooms. The boards look increasingly tempting but i am worrying about the final result. Any advice regarding boards and celotex appreciated. Thanks Brian