insulate between the joists over lay with 18mm OSB, cover with polythene, place your underfloor heating pipes using nail clips nailing them to the OSB and then lay a 40mm anhydrite screed over the top. Just make sure your joists are ok to take the weight. I have done this in several rooms in my Victorian house and it works a treat.
Thanks Alan, but we'd like to use a non-screed system due to the weight issues. Jupiter turned out more expensive than their quotover the phone quote, so we're looking at a system which exactly replicates what they do - but i've still been quoted almost GBP 11,500 for an all-in cost of installing this for a 70 sq/m flat - for all materials, floor prep, labour etc. (works out to c.190 per square metre)!!!! Feels really expensive. The specifications we are considering are below, would love to know your views (we need to minimise floor build-up and reduce accoustic transference to the floor below):
Starting from the bottom/between the joists:
100mm Rock wool resting on timber ceiling below
Air gap
18mm ply structural deck supported on battens set between the joist
16mm Pex-Al-Pex heating pipes in grooved foil covered heating panels (on top of the ply)
9mm Redupax acoustic strip to align with the surface of the heating panels
20mm Fermacell 2E11
15mm Engineered wood
UFH System components:
Heatmiser Digital Programmable Thermostat
Grundfos 15-50/60 pump
Pex-Al-Pex pipe 5 Layer
Manifold 6 Zone Dualmix
Details of the construction:
- Minimising the floor buildup is a key factor - need to keep it to the lowest possible height
- It is a conversion and we need to minimise the sound transference to the flat below
- Below us is our neighbours flat, there is no subfloor at the end of our timber joists - just the ceiling of our neighbours flat
Thanks a lot for any input or advice - right now considering giving it all up and just sticking to radiators!