Studwall partition in garage

[kinhell]

I'm going to seperate the garage to create a utility room and was wondering if a stud wall can be used instead of block work? If so, what depth should the timbers be and what PIR board to use? I've seen Wickes stud work timbers are 89mm but PIR board is either 75mm or 100mm.

 

[noseall]

We use regularised 100mm studs (95mm finished) which does mean that 100mm PIR will end up proud of the timber. We then fix another 50mm PIR across the studs one side prior to plasterboarding and often fix a layer of 18mm ply beneath the plaster board on the habitable side to assist later fixing.