WWYD - insulate garage/workshop

[garuff]

Hi all, I'm anticipating the answer is b"how long is a piece of string" but hoping I might get a steer in the right direction...

I've got a detached garage built c.2000, 5.6m x 5.4m, pitched roof, 2.7ish floor to rafter, 14ft x 7ft up and over door, metal side door.

Cavity walls, brick exterior and block interior, doesn't appear to be any cavity insulation.

Concrete floor, seems pretty thick but not sure how deep, assuming DPM but not seen one.

I use it for woodworking and storage. Looking to insulate because it gets blinking cold in the winter and stinking hot in the summer.

I'd toyed with sectioning off an area c.3m x 3m with stud walls and some sliding patio doors to just insulate that area (including ceiling), but wondering if just insulating the lot might be not much more effort...

So... What would you do?!

If I don't do the stud 'room in a room' am I making it harder because of the doors?

Will have a poke around for previous threads once I've decided on an approach...

Thanks

 

[sircerebus666]

Depends on how much space you're willing to lose , how much money you're willing to spend

I would insulate the cavity, build stud work around all four walls including blocking in the up and over and the ceiling fill stud wall with rockwool and use insulated plasterboard over the top and replace metal door with uPVC

Although you will lose that handy up and over but that will be a big reason why your workshop is so cold in winter and hot in summer

 

[oldbutnotdead]

The biggest heat gain/loss will be from the roof. Easiest way to cure that would be solid insulation fixed under the rafters & sealed to the walls (maintain eaves ventilation for the roof).
Next target is the up & over door. Roller shutters will give you better draught proofing, a set of French windows or patio doors and brick up the rest of the gap would be better still (and will reduce noise transmission).
Final one is the walls, not sure what the state of play is with cavity insulation as a retrofit these days, do check on here so you can avoid the horror stories

 

[dontbelieveawordofit]

get a nice wood burner

 

[garuff]

Thank you for the replies (I seem to have missed the notification of any replies landing!)

In terms of how much to spend, it's likely a case of attacking it piecemeal, I'm not sure my wife will be happy with me siphoning off all the funding for new decking to do the garage throughout

I think I might start at the roof and work out how much I'm willing to lose the doors fully later...

Easiest way to cure that would be solid insulation fixed under the rafters & sealed to the walls (maintain eaves ventilation for the roof).

If I'm reading this correctly, that would be celotex/kingspan type foam boards fixed onto rather than between the rafters?
The rafters have some diagonal bracing running flat across them already, flush to the undersides, I think it would be something like 1x4 planks. Would I need to batten out the lot to a similar depth before fixing boards up there?

 

[oldbutnotdead]

Yes you would have to otherwise the (rigid) boards will be up and down like a very shabby thing. Roughcut fence boards will do, head for your local timber merchant (not B & Q etc) & see what they've got.

 

[garuff]

Gotcha, thanks.

I'm not sure how I'd be able to seal the solid boards to the walls?
I may be over thinking it, but I'm picturing a whole mess of angles and the joists getting in the way of taking the boards right to the wall

 

[oldbutnotdead]

Don't get too worked up about it. Posh version is cut the edges of the boards at an angle so they sit flush to the wall. Sensible version is staple some polythene to the rafters near the wall, put the boards up so there's a gap on the underside, fill gap with expanding foam (the polythene is to stop excess foam going up between rafters & blocking ventilation)

 

[Tigercubrider]

Some people doing diy builds buy damaged insulation board off eBay. I understand that it's cheaper, and you can just cut the damaged bit out.
Again, I have heard of people buying hoardings from building sites to use the ply.,

My garage isn't insulated, but is attached. I covered my up and over door with polystyrene and insulated foil. It still opens but I spent ages ensuring that all the seals work.
In your case, maybe make lightweight doors inside that can be opened inwards? That way big items will still get in but You can mitigate the cold.
Maybe insulate the walls and ceiling, "block up" the up and over to get it done quickly, but build it in such a way that yo can go back and change the door area to open?
I just have rubber open cell flooring to stand on (half the area) and the whole concrete floor is painted because I work on bikes.

 

[oldbutnotdead]

Oh hang on, have you got joists (horizontals) as well as rafters?
If you have then just drape loft insulation across them, much cheaper

 

[garuff]

Oh hang on, have you got joists (horizontals) as well as rafters?
If you have then just drape loft insulation across them, much cheaper

Sorry, missed that bit in the description!

I'd been leaning towards insulation at the rafters to keep the useable space on the joists, but realistically it's mainly for cr@p and I haven't got much up there! With pragmatism in mind, I'm thinking I'll probably plasterboard the ceiling, insulate on top and board out the middle stretch for storage.

Any thoughts if need to be concerned about the bearing capacity of the joists?

 

[garuff]

My garage isn't insulated, but is attached. I covered my up and over door with polystyrene and insulated foil. It still opens but I spent ages ensuring that all the seals work.
...
I just have rubber open cell flooring to stand on (half the area) and the whole concrete floor is painted because I work on bikes.

Did you paint with epoxy paint or anything? Was wondering about flooring at some point next.

The up and over doesn't really have seals, did you add them or were they part of the door?

 

[HERTS P&D]

get a nice wood burner

I agree with Benny

Andy

 

[garuff]

I think I'd be banned from the garage permanently if I got a woodburner in there before sorting one in our lounge first!
Motivation to get cracking with house jobs though...

 

[oldbutnotdead]

What are those joists, look like 6 x 2 at 600 centres? Plasterboard and insulation would be ok but i wouldn't put a lot of weight up there on a 5 metre span, they might be a bit baggy, probably only there to tie the rafters in