Garage Roof Felt Replacement/Insulation Query

bloke91

Hi all,

Our garage roof felt roof needs replacing due to natural age etc.

The boards under neath and are in good condition, the garage has brick walls with cavity wall.  Other than that not plaster boarded and no insulation above the garage under the roof felt or under the roof boards.

The garage is used for storage purposes with about 15% of it sitting below one of the bedrooms and the remainder with nothing above.

Before I arrange a roofer to replace the roof felt, is it worth considering installing insulation under the roof felt? Whilst have no plans to use the garage for anything other than storage, I guess I could fit insulation under the roof boards at a later date post the felt being replaced?

Welcome thoughts and advise.

Thanks in advance for your time.

FreeBear

Certainly insulate the section under the bedroom. The rest of the roof, really not worth the expense or effort - The door will be letting loads of cold air in (hence the reason to insulate under the bedroom).

ThisIsWeird

Not sure I fully follow the layout, but as FreeBear says, there's little point insulating the ceiling of a room that doesn't have any heating.
Insulation doesn't make a place 'warm' by itself, but reduces heat loss and gain if a heat source is added, so no real benefit unless you plan to add a heater.
But, yes, def heat under the floor of the bedroom, as tightly up against the underside of that bedroom floor as possible. That will help to keep the bedroom floor warm.

MCT56

Cut to length profile steel sheets are a popular choice these days. Try Google to see if these would be suitable and if you have a local supplier / fitter.  These can be manufactured with insulation on the underside, if desired and a plasticised, leather grain finish on the upside. Various colours available. 

Section62

ThisIsWeird said:

Not sure I fully follow the layout, but as FreeBear says, there's little point insulating the ceiling of a room that doesn't have any heating.

Insulation doesn't make a place 'warm' by itself, but reduces heat loss and gain if a heat source is added, so no real benefit unless you plan to add a heater.
...

I'd slightly disagree.... a space without heating will still contain some heat energy, and if there were a need to try to keep the space warmer than the outside then insulating the ceiling/roof would be a good idea.  For example a shed you do some pottering around in but don't want to heat will be more comfortable in cold weather if it has some insulation.  Even on winter days the sun will add some heat energy to the structure, careful use of insulation can help to retain some of that heat overnight.

Insulation also works both ways - insulation can help to keep a space cooler on blazing hot summer days.

As FreeBear mentions, the garage door will probably be the leakiest thing... but if there might be a plan to do something about the door one day then whilst the roof is being redone it might be sensible to add a bit of insulation to it.  Insulating the roof above the existing boarding will be easier than trying to fit it between the rafters.

TELLIT01

Commenting only on the material to reroof the garage with.  The OP refers to refelting, but there are much better materials available.  We recently had the felt on a shed roof replaced with a rubberised material, sorry I don't know the proper name, which is said to be much longer lasting.

stuart45

TELLIT01 said:

Commenting only on the material to reroof the garage with.  The OP refers to refelting, but there are much better materials available.  We recently had the felt on a shed roof replaced with a rubberised material, sorry I don't know the proper name, which is said to be much longer lasting.

Is it EDPM?

TELLIT01

stuart45 said:

TELLIT01 said:

Commenting only on the material to reroof the garage with.  The OP refers to refelting, but there are much better materials available.  We recently had the felt on a shed roof replaced with a rubberised material, sorry I don't know the proper name, which is said to be much longer lasting.

Is it EDPM?

That's the stuff.  Thanks.

bloke91

Thanks for everyone's inputs.

It sounds like the general consensus is to leave the remainder of the Garage roof as it's not being used for anything other than storage and not heated.     

Then ensure the section of garage ceiling siting under the bedroom is insulated to prevent cold air from the garage going into the upstairs.  I have circled the area below the bedroom in red within the attached image.



What thickness and type of insulation boards would you recommend for this? Something like this? - https://www.tradeinsulations.co.uk/product/50mm-celotex-ga4050-insulation-board-2400mm-x-1200mm/?gad_source=1&gclid=EAIaIQobChMI8Yr-0ZTkigMVBp1QBh164wpHEAQYByABEgKQi_D_BwE

Then simply plaster board over that section of the garage roof and leave the other side that has the beams showing as is?

Thanks in advance for your time.

FreeBear

Looks like you have double thickness of joists there. At a guess, close to 300mm ?

I'd pack the whole space with either fibreglass or mineral wool to the full depth of the joists (both are non-combustible, unlike Celotex).  Finish off with either fire resistant plasterboard or a cement board.

bloke91

Hi again all,

What type of insulation would you recommend and be best to use?

I heard Celotex and Kingspan are very good, resistant to mould and fireproof, but also heard fibreglass or mineral wool could be even better from a fire resistance perspective?

With there being a bedroom above I am keen to get the insulation right.

Thanks