Insulating the garage

JhnBssll

Veteran
Location
Suffolk
So I've decided that whilst I'm already mid-DIY adventure with the front extension it would be a great idea to break away for a week or so and insulate the garage :okay: In the last few years I've made some improvements by replacing the main garage door with an insulated electric roller-shutter and the personnel door with a nice insulated composite door but there's no getting away from the fact it's a single skin stand-alone garage. If it's freezing outside it's freezing inside :laugh: Since I've made the space much more usable recently it seems daft not to finish it off with some insulation so I can use it comfortably year-round.

To that end I've ordered lots of insulation :okay: Plan is:

- Empty the roof of a decades worth of crap :laugh:
- Remove the haphazard boards that the previous owner balanced across the joists and screw down some proper boards for storage, braced if needed
- Insulate the rafters with 50mm celotex leaving a vent space above
- once the roof is done I'll move all the crap I haven't discarded back in to the roof and tear out the cupboards and benches to expose all the walls
- batten the walls with dpc between batten and brickwork, then 40mm of taped celotex with foil vapour barrier, then 15mm OSB screwed through to the battens
- Paint OSB
- Re-run the electrics in surface conduit
- Fit some sort of smart heater so I can preheat the room remotely when needed to save heating it continuously

Then I need to think about the best use of the new space and what to replace the benches with, the stuff in there at the moment was all built in by the previous owner and, unlike the roof boards, is absolutely solid - I imagine it'll be fun trying to remove it :laugh:

I've read a few articles and know the insulation thickness I'm using is below that required of the current regs but really all I'm hoping to do is stop it being freezing cold - I could see my breath in there earlier :laugh: I'll continue to use the turbo trainer in there, and I also run 3D printers in there which don't like the cold at all. I want to avoid damp which is probably my greatest concern as I don't really want the roof timbers rotting through at any point :whistle: To this end I'll be extra careful to tape all the insulation joins and try to avoid cold spots, but some will be inevitable due to the construction of the roof timbers. Would be good to hear others thoughts on this so if you have any experience, tips, advice, please let me know :okay:
 
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matticus

Veteran
<follows>
 

slowmotion

Quite dreadful
Location
lost somewhere
It's probably got a concrete floor. If you are not going to use it for a car, I would put some 50x50 mm battens down, lay 50mm rigid insulation between them, and board over the top with water resistant chipboard or MDF.
In winter, you'll be doing your feet a massive favour. Also, it's much more comfortable to walk/stand on a floor that's not entirely rigid, however cold it is.

Edit: Actually, forget about the battens. Just lay the MDF/chipboard directly on the rigid insulation.
 
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raleighnut

Legendary Member
Location
On 3 Wheels
It's probably got a concrete floor. If you are not going to use it for a car, I would put some 50x50 mm battens down, lay 50mm rigid insulation between them, and board over the top with water resistant chipboard or MDF.
In winter, you'll be doing your feet a massive favour. Also, it's much more comfortable to walk/stand on a floor that's not entirely rigid, however cold it is.

Edit: Actually, forget about the battens. Just lay the MDF/chipboard directly on the rigid insulation.
I'd do the floor first, that way the wall insulation/boarding will be off the concrete floor and will be warmer. it's like the 'pro' way of installing laminate/engineered wood flooring (take the fricking skirting boards off) so you dont have that unsightly 'quarter round' moulding that's the mark of a DIYer
 

bikingdad90

Veteran
Personally I would get the extension finished as no doubt as soon as you start pulling stuff out you will find a load of problems and you will find it will take twice as long as anticipated to do the work!
 

BianchiVirgin

Über Member
Location
Norn Iron
Use a composite board on the ceiling which will be an insulated plaster board mix. This will eliminate the cold spots where the joists are. You could add more above in the attic space too but that would save you having to empty it and also doesn't semi-bury any existing wiring. You'll lose about 50mm is ceiling hight though.
 

jowwy

Guru
So I've decided that whilst I'm already mid-DIY adventure with the front extension it would be a great idea to break away for a week or so and insulate the garage :okay: In the last few years I've made some improvements by replacing the main garage door with an insulated electric roller-shutter and the personnel door with a nice insulated composite door but there's no getting away from the fact it's a single skin stand-alone garage. If it's freezing outside it's freezing inside :laugh: Since I've made the space much more usable recently it seems daft not to finish it off with some insulation so I can use it comfortably year-round.

To that end I've ordered lots of insulation :okay: Plan is:

- Empty the roof of a decades worth of crap :laugh:
- Remove the haphazard boards that the previous owner balanced across the joists and screw down some proper boards for storage, braced if needed
- Insulate the rafters with 50mm celotex leaving a vent space above
- once the roof is done I'll move all the crap I haven't discarded back in to the roof and tear out the cupboards and benches to expose all the walls
- batten the walls with dpc between batten and brickwork, then 40mm of taped celotex with foil vapour barrier, then 15mm OSB screwed through to the battens
- Paint OSB
- Re-run the electrics in surface conduit
- Fit some sort of smart heater so I can preheat the room remotely when needed to save heating it continuously

Then I need to think about the best use of the new space and what to replace the benches with, the stuff in there at the moment was all built in by the previous owner and, unlike the roof boards, is absolutely solid - I imagine it'll be fun trying to remove it :laugh:

I've read a few articles and know the insulation thickness I'm using is below that required of the current regs but really all I'm hoping to do is stop it being freezing cold - I could see my breath in there earlier :laugh: I'll continue to use the turbo trainer in there, and I also run 3D printers in there which don't like the cold at all. I want to avoid damp which is probably my greatest concern as I don't really want the roof timbers rotting through at any point :whistle: To this end I'll be extra careful to tape all the insulation joins and try to avoid cold spots, but some will be inevitable due to the construction of the roof timbers. Would be good to hear others thoughts on this so if you have any experience, tips, advice, please let me know :okay:
All sounds like top work, but as others have said I would do the floor first. Put damp proof membrane down on the floor first and then 50mm celotex all over and then ply board or osb it. Then when you come to do the walls, you can seal the lower sills of the wall to the floor to prevent cold spots. On the walls make sure you leave an air gap between wall and insulation of around 25mm. You can do that by screwing some extra battens in between the insulation and wall before adding it so it doesn’t push back onto the wall while taping........

also is there anyway of you doing the roof from the outside rather than inside?????....

remove felt/shingles......50mm batten all around the edge, lay 50mm celotex insulation, cover with osb And then re-shingle/felt. That way you keep the joist in the garage uncovered and no need to leave an air gap, which is more difficult on the inside of the roof.

also don’t forget ventilation if your going to add heating.
 
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glasgowcyclist

Charming but somewhat feckless
Location
Scotland
Plan is: [snipped]
Sounds exactly what I ought to do with my garage except I wouldn’t know how.
So how much would the job cost if you got a professional in to do it?
 

jowwy

Guru
Sounds alright. Only problem I need to solve is where to put all the stuff that’s in there while it’s done!
Materials may cost more were you live, so factor that into the equation. I have seen quotes for this work close to 3 to 5k........but it shouldn’t be anywhere near that.

i did 3 walls of the man cave and floor for less than £500, but I did it all myself. This year I’m rebuilding the front wall with new windows and doors and insulation the roof.
 

glasgowcyclist

Charming but somewhat feckless
Location
Scotland
Materials may cost more were you live, so factor that into the equation. I have seen quotes for this work close to 3 to 5k........but it shouldn’t be anywhere near that.

i did 3 walls of the man cave and floor for less than £500, but I did it all myself. This year I’m rebuilding the front wall with new windows and doors and insulation the roof.
I’ll check with my local builder guy, he just lives up the road and did our major house renovation a few years ago.
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
Detatched garage with 'loft space' Too many bikes, roof racks and tools in mine. MrsF bought me 3 floor to ceiling shelving units a few Xmas'es ago and even with them and a steel cabinet, there is still too much 'stuff'.

Watching with interest ! ^_^
 
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