Garage ceiling insulation

[AdamW]

Thanks for the additional advice guys.

Regarding the fibreglass insulation for sound proofing, do you think this will be ok? - http://www.seconds-shop.co.uk/products-page/rockwo...

Price is incredibly good but it is for cavity walls, not ceiling. However I cannot see any noticable difference between their wall and ceiling products.

Regarding the foil tape, do you think necessary to tape where the ends of the PIR board meet the walls (either end)? From experience foil tape does not adhere to brick/breeze block particularly well. Expanding foam would be an alternative but I always like to be able to remove things if ever needed, and it would be a nightmare if expanding foam was used.

[mk1fan]

Cavity wall insulation differs in that it is made not to slump down when in a vertical position. No issues using it horizontally.

I tape the edges down the wall but leave it short enough to allow a proper filled joint between the plasterboard and ceiling. This is easier if 2 layers of board are fitted.

[stanwan]

For mineral wool sound insulation I would recommend RWA45 slab insulation, this is dirt cheap and more effective than loft roll. You should also enclose mineral wool with a vapour barrier as well. You could also mount the plasterboards on resilient bars to reduce noise further.

electric garage door openers create a lot of vibration and noise through a building - consider using flexible rubber mounts for the assembly.

[AdamW]

Hi Stanwan,

By enclose what do you mean? Vapour barrier all the way around the fibreglass insulation, or just between the fibreglass/floorboards or fibreglass/PIR board?

[mk1fan]

In this instance it would be laid over the mineral wool & joists under the floor boards.

If the PIR joints are taped on the top sides too then the vapour barrier would (in practical terms) not be needed over the mineral wool insulation.

[AdamW]

Hi MK, thats not too clear to me.

Do you mean the vapour barrier goes in after the fibreglass insulation, effectively creating a carrier between it and the PIR?

Or it goes in before the fibreglass, creating a barrier between the fibreglass and PIR?

Given the garage will not be used as a place to store a car/start a car, is this really needed?

[mk1fan]

The vapour barrier would go under the floor boards of the room over. So working from the top you would have floor board - vapour barrier - mineral wool insulation - PIR insulation - plasterboard.

[AdamW]

MK41, just to check can you confirm my understanding is correct.

Red is the moisture barrier
Orange is the fibreglass
Green is the PIR board
Silver is the foil tape

I assume the moisture barrier does not need to be fixed in position as such, as the insulation underneath with keep it where it should be.

[mk1fan]

No, the vapour barrier would lie over / above the joists as the floor boards do.

[AdamW]

It is not possible for me to do that as I do not have access from above at this stage. Is the vapour barrier necessary given it will not be used for storing car etc?

You didn't mention it in your original suggestions.

Otherwise I'm a bit screwed!

[Spudler]

AdamW said:

Is the vapour barrier necessary

No.

[mk1fan]

AdamW said:

Is the vapour barrier necessary given it will not be used for storing car etc?

See my reply a few boxes above. No it's not required. I didn't suggest it.

If access is available from above at a later date then I would tape the upper joints of the PIR board.

[Tennicee]

Mk1fan, I thought I'd bring this thread back to life again as your advice sounds great and I'm wondering if it could be adapted to my situation as my house has a loft with a structural floor so we need to insulate the roof rather than loft floor.

It is divided in 2 (bedroom and storage). As part of some other work, we had a builder fit PIR insulation to the entire roof space and replaster the bedroom side while the storage side has only been finished to plasterboard so all the screws are easily accessible. The problem is that there are noticeable draughts coming through from the gaps in the plasterboard on the storage side. These gaps are only c2-4mm wide and looking through, I can see he hasn't joined any of the PIR boards together.

So my questions: I was going to take down the plasterboard and use expanding foam in the small gaps between the boards and then replace the plasterboard. But, can I use ali foil tape instead and then also tape up the plasterboard? (Actually, would I even be able to screw the board back through original holes or will I need to make new ones and fill in the old??)

Or would it be sufficient to tape just the gaps in the plasterboard and leave the insulation as is?

Or, given I can only get to half of the roof and presumably insulation has been installed the same way on both sides, is it pointless to tinker with it from an energy saving perspective as heat will just find its way round to the fully plastered side and exit there?

Given the house is solid brick so we currently can't insulate the walls and the floors won't be done for a few years, I'm trying to maximise what I can do in the loft so all advice gratefully received, thanks!

[jaylockwood1978]

Good afternoon,

I’m a new member and come across this really helpful historical post, so sorry to reopen it but
Our 1930’s house has an integrated garage (used for storage, not a car), with a bedroom above. We’ve had the asbestos ceiling removed so now have the joists and can see straight up to the floorboards of the room above. I want to insulate and plasterboard the ceiling. Would it be ok to feed through a layer of rock wool to lie on top of the joists and then fit celotex or something between the joists and then fit plasterboard to the underside of the joists?

if so, what thickness for each would you suggest please? I’m not bothered about skimming the board or anything.

Any advice about what to do regarding wiring would be great too (I’ve attached some photos).

Thanks
Jay

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