Insulating a room above an unheated garage

B

BrokeBeginner

New Member
Hi all,

Having just finished the structure or a double storey side extension and I am now looking to insulate the floor of my new master bedroom which sits above an integral but unheated garage.

Does the below floor / ceiling makeup (top down make sense) noting I have 200x47 solid timber joists

18mm ply
VCL
75mm mineral wool batts between the joists
100mm PIR also between the joists
25mm roof batten to support the insulation and provide a service void
25mm counter batten to increase the service void ready for down lights
12.5mm Fire rated plasterboard

I have read mixed reviews on mixing insulation types / the need for a VCL and derating wires or creating fire hazards by covering electrics with insulation. So second guessing myself now.

Thanks in advance for any help
 
Order should be:
- 18mm ply, I would use 18mm tongue and groove osb
- don’t need a VCL, the ply plus whatever you’re putting on top will be enough of a retarder,
- 100mm pir, this stops the heat from warm room
- mineral wool, this stops the noise from the garage
- leveling this might annoying, would be easier with an mf ceiling
- fire board is good

Reversed the order of the insulation and mineral wool.
The 18mm osb3 with the tongue and groove is more than enough for vapor control.
 
Painter,

Thanks for the response. Really helpful. What was your reasoning behind osb3 over ply. Only because I have the ply already. Happy to use it elsewhere if it’s a showstopper but thought I’d ask?

Thanks again.
 
BrokeBeginner said:
Painter,

Thanks for the response. Really helpful. What was your reasoning behind osb3 over ply. Only because I have the ply already. Happy to use it elsewhere if it’s a showstopper but thought I’d ask?

Thanks again.
Click to expand...
Less expensive, easier to fit tight with the tongue and groove, and arguably more suited to the task of being a subfloor.
With the tongue and groove you also don’t need the seams to sit on joists.
 
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