I’m planning on building a wall in front of my garage door to create a small laundry room in the front of my garage, and was looking for some advice/best practice approach. 

The back of the garage has already been converted by the previous owners into a toilet and kitchen extension, that is all accessed through the kitchen. 

The garage door isn’t a great seal from the wind, cold, and bugs, but it is south west facing so does get warmer throughout the day. There is also a fairly busy road out the front (not immediately out the front but close enough you can hear cars through the garage door) so I’d want some form of sound insulation in the wall. I’ve used Rockwool RW3 before and was impressed with it.

The opening is 2.2m wide by 1.9m high. The opening is about 150mm deep between the door trim and the inside of the room. The depth between door trim and the start of the concrete slab is about 60mm, which only leaves me about 90mm before any work I do makes the room smaller, if that makes sense (see the last pic).

So working from the outside in - I guess I was planning on keeping the garage door untouched so any moisture that forms on the inside of it can be aired out by the gaps in/under and around the door. Which means I’d need a pest control mesh to keep out bugs. 

Then a breather membrane. Then some sound insulation. Then a gap? Then PIR insulation board. Then OSB to give a solid fixing for any drying rails etc for clothes, then a vapour barrier? .. and lastly green plasterboard. 

I think I could skip the vapour barrier if I use foil tape on the PIR?

I was planning on using CLS for the stud work, whether that’s 38x63mm or 38x89mm. 

Should I skip the sound insulation and double up the PIR?

Thanks in advance for any advice 😃

Garage laundry room conversion