Retro fit flat roof insulation?

[markdon]

Hi all, we have started decorating the extension that was built before we bought the house, and are finding a few problems.

The room in the winter is inhabitable, it's as cold as outside nearly! It has two radiators, one 70x100 double panel, and one 70x1600 single panel that I have just bought a double panel replacement for.

I have removed the plastic skirting as it wasn't fitted very well, and what a draught! From what I can see its plasterboard with about 1-2cm gap to breeze block. There are small polestirene balls in the gap so I assume they have had the cavity done.

So walls all cleaned, filled, undercoated and painted, ceiling next, so I pop a few of the spot lights out (two lots of 6, on two dimmer switches) to find a 9" gap between the ceiling and wooden roof.

This house has been such a pain, I wish we'd investigated further before buying. The extension is the old garage doubled and converted, but its just not warm enough. Once the skirting is back on I have some quadrant beading to go between it and the laminate to try and reduce the draught, also going to seal around the windows as there is a draught coming from around most of them.

So, my question is, should there be insulation in the roof cavity? If so, what is the quickest / easiest / cheapest options to look at? Ideally something with minimal impact to the room! I would be happy to get rid of the spots and fit two normal light fittings if its an issue having them there with insulation around them.

All help & advice appreciated, thanks.

 

[markdon]

Oh, is there a way of looking at the plans for the build? Would they have details as to materials used etc? Thanks.

 

[JohnD]

yes, during the purchase, your solicitor should have asked foe evidence that the conversion had Planning Permission and Building Regulations approval. Wasn't that done? Maybe it is non-compliant, so the standard could be anything.

You can probably search on you local council's website, using the postcode or other details. You may be able to download or buy at least initial documents, and see who applied (it might possibly have been an architect, though I doubt it, or some other professional who keeps copies.

 

[markdon]

Thanks for that, rang planning dept but no records held as didnt need permission as its on the back of the house and is single storey. Doh.

 

[JohnD]

should have had BR though.

 

[markdon]

Said there was nothing on file apart from a porch in 1979. So thats out the window then. Nothing simple with this house!

 

[markdon]

So after a quick interweb search, my quick job of smashing the ceiling down, putting some insulation boards up then plasterboarding is out of the question?

Is the warm roof thing really the best way to go? I have the access to use 100mm insulation with at the minimum 100mm air gap, though its all brick around the extension, so to aid air movement would i drill holes in the brick, through the joists then out the brick at the other end?

I know this has been covered quite a few times, but i do t think its in the same circumstamces.

Thanks.

 

[markdon]

Been advised that lining the gap with 100mm king span, which will leave a minimum of 100mm gap above it, then use a foil backed 15mm plasterboard butted up to the king span and skimmed over the top.

Been quoted at 250-300 to take the ceiling down, insulate, board and skim. Reasonable?

Is the foil backed plasterboard worth doing?

 

[JohnD]

yes, but not if you are then going to cut great holes in it for the warm damp air to rise through.

 

[markdon]

I was thinking about that, will require lighting, but going to ditch the spots for two traditional lights, one at the front and one at the back. How do you insulate this area?

Thanks.

 

[datarebal]

warm deck...

 

[markdon]

Could you give me an idea of cost for a 25sqm warm deck?

Do you simply leave the roof as it is, put insulation on top, then cover with slabs? Or is it best to recover with felt?

 

[markdon]

Roof

View inside spot hole

 

[freddiemercurystwin]

Just shove your Kingspan in hard up against the deck, don't have a gap between the insulation and the deck, its how any garage conversion roof would be done. Its neither a cold or warm roof, not ideal but stop thinking about it and just do it.

 

[markdon]

Will i need to pack the whole of the gap? Its 30cm in places. Could i use standard fibre/wool roll insulation then kingspan than foil backed plasterboard?

Sorry about all the questions, just dont want to regret it in 5-10years time.

Thanks.