Insulating a flat concrete roof

jay0109

Looking for some advice re. what to do with an old 1960's concrete flat roof. It used to be over the garage but the previous owners split the garage into a downstairs loo/shower room and a utility room. Both are very cold at this time of year and only the bathroom has a radiator but the heat is gone nearly as quickly as it goes in.

The flat roof is concrete and there doesn't appear to be any structural issues with it i.e. no leaks, no pooling of water.
I would like to insulate it in a bid to try and make the 2 rooms underneath it warmer. Internal insulation would involve having to change around electrics (light fittings for example). So was hoping external insulation could be the solution.

a - will insulation solve the cold issues?
b - if yes, what type of insulation/construction do I need to go with? (I haven't spoken with any builders or roofers yet)

thanks

Calahonda52

Any pictures?
Is it detached?
Any boundary issues is is built on the boundary wall

Dudda

You'll keep the existing concrete roof and over that put a vapour control layer and insulation on top of that. Probably 150mm PIR. Then the roofing membrane over that which could be a PVC membrane or you could use asphalt or anything really. Where you have to be careful it where it meets the existing house. Is the rest of the house two storey or does it adjoin a pitched roof, etc. Also need to consider roof falls, gutters, rain water outlets, any rooflights, etc. I suppose if we had photos we could advise more. It's all doable, easily done by any builder or roofer and will make the rooms warmer.

jay0109

Calahonda; See pic attached which is taken from a bedroom looking out on the flat roof.
As you can see it's a on the ground floor with the upstairs part of the house surrounding it on 2 sides.
No boundary issues as detached house

Thanks for the response Dudda, that's the kind of info I was after which will give me something to go talk to roofers about.

Dudda

jay0109 wrote: »

Calahonda; See pic attached which is taken from a bedroom looking out on the flat roof.
As you can see it's a on the ground floor with the upstairs part of the house surrounding it on 2 sides.
No boundary issues as detached house

Thanks for the response Dudda, that's the kind of info I was after which will give me something to go talk to roofers about.

You've a handrail to the edge of the roof. That brings up a few more questions. Is this a terrace or area you can walk out onto? Is it an escape route from bedrooms? Is the railing retained or removed during the works? Railings like that are more fixings or connections through the waterproof layer to the concrete structure below and therefore more work and cost to make watertight and also a longer term leakage risk.
If regular access to the roof is required then you wouldn't go for a PVC layer like Trocal as that's easily damaged compared to asphalt.

jay0109

Yes, you can walk out onto the roof area as the bedroom I took the pic from has a door out to it. But we don't use it as a terraced area.
I go out there a few times a year to hang xmas lights along the front of the house, to clean the gutters etc.

The railings complicate it alright and I want to keep them there as the other houses in the row have them also.

Calahonda52

If you budget stretched to it, them the railing cloud be redone so as they are fixed on the wall below the roof and bent around the slab.

The other, sub optimal way is to keep inside the railngs as they are.

Not ideal but better than current.

How much of a step down is there from the door to existing?

jay0109

Calahonda52 wrote: »

If you budget stretched to it, them the railing cloud be redone so as they are fixed on the wall below the roof and bent around the slab.

The other, sub optimal way is to keep inside the railngs as they are.

Not ideal but better than current.

How much of a step down is there from the door to existing?

I'm thinking about moving the railing like that alright. It's definitely an option to protect the integrity of any insulation.

The drop at the door is about 100mm

whizbang

75mm structural/flooring PIR, Overhang as much as you can get away with, 25mm Poured slab with additional 50x250mm band to anchor new railings.
Waterproof coating.
Thats about all you can do. You cannot raise the level above the door frame.

BryanF

No mention of what the Roof fall is

jay0109

If anyone has a roofer recommendation for the Dublin area, can you PM me? Want to get someone out to look at the job and give a quote with a view to having the work done before next winter.

Thanks