Ceiling insulation in garage

[Auchlossen]

A small part of my double+ garage has a flat concrete roof over it, c. 6x1.5m. Most of the rest of the garage is built in to the ground with studio flat above, so is not losing heat too much.

I would like to make it warmer in there to encourage workshop and cycle training activities. Might even put car in there when it gets seriously cold.

I had thought of putting Celotex slab there, if my LBMerchant can offer some cheap damaged bits, with double plasterboard under on a timber frame.

However concern about Grenfell puts me off this option.

Should I just use mineral wool eg Rockwool over the timber framing as a suitably cheap solution?

[ProDave]

The issue with a garage is the vehicle door.

 

My garage walls and ceiling are insulated to the same standard as the rest of the house, except no air tightness membrane.  It is still cold as heat leaks from the "insulated" garage door like it is going out of fashion.

 

So I would say cheap rockwool type is all you need.

[Jeremy Harris]

My garage/workshop has 150mm of rockwool in the walls and 200mm in the ceiling and it doesn't get too cold in there, but as @ProDave says, the door (an "insulated" roller) is just hopeless.  My main problem is that the door faces South and gets pretty hot, even in winter, and acts like a giant radiator that quickly over heats the garage.

 

I'm seriously thinking of replacing the roller door with some insulated timber garage doors, but they would need to be hinged and open outwards, as I don't have any room inside for anything else, and the door opening is 3m wide, which I think is too wide for just a pair of doors.

[Simplysimon]

6 hours ago, JSHarris said:

 

@ProDave

but they would need to be hinged and open outwards, as I don't have any room inside for anything else, and the door opening is 3m wide, which I think is too wide for just a pair of doors.

sliding track along the wall, used to be king track, with rebated doors to allow for the corner

[Jeremy Harris]

2 minutes ago, Simplysimon said:

sliding track along the wall, used to be king track, with rebated doors to allow for the corner

Sadly I have benches fitted on both walls, so have no room for anything that slides inside.  The "garage" is really a boat building workshop, 6.1m long and 4.1m wide, hence all the insulation and internal creature comforts (I've even fitted aircon...).  I've been looking around to try and find anyone that can make a pair of 1.5m wide timber doors, that I could then add some internal insulation to, but have had no luck so far.

[Simplysimon]

@JSHarris you're really looking for a framed door clad in galv tin which would allow ins to be placed inside frame

[PeterW]

Could you not have them 750mm wide and double hinged and monkey bolted..?? That would allow the middle 1.5m to open then if you pull the monkey bolts then it would allow the doors to fully open ..??

[Jeremy Harris]

Just now, PeterW said:

Could you not have them 750mm wide and double hinged and monkey bolted..?? That would allow the middle 1.5m to open then if you pull the monkey bolts then it would allow the doors to fully open ..??

 

Damned good idea!  That may well work a treat, and have the added advantage of the doors not projecting out as far on the rare occasions that they are opened.

[Auchlossen]

Just to get back to the original post ?

since this is a retrofit, and there is not an opportunity to put insulation over the concrete slab [warm roof],

it looks like the 'undesired' cold roof is the only viable option.

So I plan to put framing for a plasterboard ceiling, and insert rockwool leaving a ventilated airgap to the concrete roof?

[Jeremy Harris]

That's pretty much what I have. 

 

I had the ceiling boarded, with 200mm of rockwool between the ceiling joists, which are 220mm deep, as they are boarded out on top to give a small loft storage space.  I have a cold roof above this, albeit with a totally useless layer of multifoil insulation stapled across under the rafters (all that's useful for is reflecting light better from the loft lights).  I have ventilation under the eaves and at the ridge, so the space behind the slates is pretty well ventilated.