Small garden room

[focaltucker]

Hi
I am building a small garden room. 3m x 3m by 2.5 high with a pitched roof.

I have built the based from 5x2 joists and sat it on levelled dense blocks. I am insulating with kingspan.

I am after some advice about the wall insulation and ideas for roof construction.

What's the most cost effective way to insulate between the stud walls?

I am using 3x2 stud, 11mm osb, vapour barrier, battens then exterior cladding.

With the roof, I have no idea what to do. I want something lightweight, not too expensive but maintenance free? Any thoughts?

 

[Notch7]

50mm PIR insulation between the studs I reckon.

Cut it 8 to 10 mm narrow, put a screw or 2 to hold it in place, then use a foam gun all round (a proper metal foam gun that can be turned right down).

The foam once set will make a complete seal and make the structure surprisingly rigid.

set it flush to the outside leaving a service gap on the inside.....

 

[focaltucker]

Thanks. I wasn't sure to go down that route or 75mm cavity slab.

I using a foam gun on the floor in the same way.

Interesting though is I had assumed 25mm air gap would go on the outside between pir and osb board.

So you'd suggest that was on the inside?