UFH and new stud walls

[DavidKilburn]

This hopefully will be a straight forward answer to you guys in the know... hopefully!

 

I have an old stone build (stone and rubble) farm house, with concrete floors.  We are planning on UFH with air source.  We're planning on 100mmpir on the concrete, membrane, then pipes and screed, raising all door heights to take account of the new 150mm (100mm pir and 50mm screed) higher floor level.  But, we plan to stud out some of the externally facing walls - building an internal stud frame and insulating between the studs (100mm pir), before new plasterboard and then skimmed.

 

Question #1  is...

do I stud first, to the plasterboard stage, then insulate the floor, pipe and screed, or...

do I insulate to the existing walls, pipe and screed, and then erect the stud work on top of the screeded floor, remembering to leave the pipe work away from the edges to take account of the new internal walls? 

 

I'm guessing stud first, but I'm no expert!  Any advice appreciated.

 

Question #2 is...

All but one floor is concrete - the only other ground level floor is a suspended timber floor, with joists.  Don't ask me why they did all but one... I have no clue!

We want a consistent floor level throughout the ground floor, so will need to bring the suspended floor up to the same height.  We plan on again using 100mm pir, but that leaves 50mm (which would have been screeded in the remainder of the property).

 

If I go with a wooden board clip-in system for this one room, how best to make up the 50mm??

If the board system where the pipes are placed is 20mm say, and the whole floor is then covered with 9mm ply, (20-9 = 29) that leaves me with 21mm to pad out to get me to the overall uniform level of 50mm? 

 

Do I go for 120mm pir, or

Do I go for a 20mm board below the PIR to make up the difference?? 

 

Thanks in advance!

 

 

[BotusBuild]

Q2 first as that's easiest 🙂 Fit more PIR. Always fit more insulation if you can 🙂

 

Q1. My approach would be as follows:

• Membrane bringing it up the walls by 250mm
• 100mm PIR
• Around the edges fit an extra 50mm of PIR the width of the studs you propose to fit. (for belt and braces approach, seal the joints between the PIR)
• Lay pipe and screed in the resulting "paddling pool"

You should now have a screeded floor with an edge of PIR showing, the width of your proposed studs

• Now fit your stud work atop the PIR edge, fit the PIR between and plasterboard the walls.