Garage to utility room.

[noseall]

Just wondering if the 25mm celotex is necessary. I get that any additional insulation is a bonus and I get the science behind the fact that you are covering cold bridges caused by the studs. I just seems that when about 25% of the wall will be a door (fire door required I assume) through to the garage which is essentially a cold spot in the wall the additional 25mm may be overkill? In a room this size I suppose every inch saved is important.

It depends on the vagaries of usage. If you say end up having a cupboard or some such up against that wall, then mould may occur on the wall, where it shadows the upright studs. Building Control will likely insist in any case.

You can place the additional insulation on the cold side? You just need to be robust with the VCL (foil taping, Duplex boards etc).

 

[flixton]

Thanks Noseall, I take your point and agree. for the sake of an inch I'll go with the 25mm insulation. I can use the offcuts for my floor perimeter.

 

[robinbanks]

At this rate, this is going to be the country's first passivhaus utility room

In a room this size I suppose every inch saved is important.

If you need an inch for the room, will you even miss it from the garage?

 

[flixton]

Build a small retaining wall

Could this be a single skin wall (it'll end up about four brick high) or would it have to be double skin.

 

[noseall]

Could this be a single skin wall (it'll end up about four brick high) or would it have to be double skin.

Single skin will be fine. It's purpose is to retain the concrete floor etc and become the bearer for your stud wall. It needs to be as high as the finished floor level.

 

[flixton]

Single skin will be fine. It's purpose is to retain the concrete floor etc and become the bearer for your stud wall. It needs to be as high as the finished floor level.

Thanks for that, I've just picked up the bricks etc. and wondered whether I should be building it double for a bit of strength. I do have a tendancy to overthink things .

 

[robinbanks]

A stud wall built straight off the garage floor would have the requisite strength to retain the slump of the 20 or so kilos of concrete resting gently against it, don't worry

And it would be faster, easier and better thermally than the construction proposed

Even a sheet of ply propped up by a couple of concrete blocks would be an adequate shutter. You don't need a 9" brick wall to retain a floor slab

I do have a tendancy to overthink things .

It hadn't escaped notice!

 

[mrrusty]

I understand I will have to get building control involved at some point

Not wanting to put a spanner in your works, but integral garages are controlled - the floor level difference is a requirement as are firedoors etc. If you were just plumbing for a washing machine and possibly a loo in the corner, and nothing else, then it's still a garage, but once you start insulating, which implies it's going to be heated (otherwise why bother with insulation) you open the door to the full gamut of building regulations, including e.g. requirements for ventilation etc. If you haven't yet made any sort of BC application - either a notice or full plans, I suggest there may be trouble ahead.....

 

[robinbanks]

Insulation or no, new foul drainage is controlled. OP hasn't responded to the question of whether it will be a heated space but does seem to be aware BC oversight will be required

 

[mrrusty]

Insulation or no, new foul drainage is controlled

Yes, of course, but if nothing else requires BC oversight, would you bother just to cut-in a new pan, or risk the "toilet police" knocking on the door.... you don't need to answer that

 

[flixton]

Not wanting to put a spanner in your works, but integral garages are controlled - the floor level difference is a requirement as are firedoors etc. If you were just plumbing for a washing machine and possibly a loo in the corner, and nothing else, then it's still a garage, but once you start insulating, which implies it's going to be heated (otherwise why bother with insulation) you open the door to the full gamut of building regulations, including e.g. requirements for ventilation etc. If you haven't yet made any sort of BC application - either a notice or full plans, I suggest there may be trouble ahead.....

Thanks for the info. The new room will be heated and insulated and become part of the house. I realise that BC will need to be involved and have already looked into this. The pupose of my posts is to get as much info. as I can before I start the ball rolling. I also want to be comfortable knowing all the work is within my skill set. So far from the helpful replies I have had I now have the confidence to start moving forward. I still need to get my head around the walls and ceiling and have started another post regarding these.