existing cavity block extension

johnboy8

hi can anyone give me a few pointers.i have an extension(5m *4m)with a flat roof,there is no insulation in the ceiling.do i take down the ceiling,insulate and replaster,or is there any other method(what about those plasterboards with the insulation attached)also is there anything i can do to the walls.thanks.

tobinj6

Hi in relation to the ceiling you could a) Put insulated board on top of existing ceiling or b) knock out the plaster board in the existing ceiling and get rockwool insulation fitted into the ceiling, then use a foil back board for the ceiling. if i where in your situation i would choose option b and do it right.

In relation to the walls i assume you mean bout insulation as well if so there are a few options also you could mushroom fix an insulated board to the walls or you could batten the walls out and insulate them and then use a vapour barrier and board over, now i assume that the 5m * 4m is very valuable space and you dont wanna lose all that much so the foil back board option will suit you better.
There are also other options in terms of if it is a cavity built extension you can get an insulation pumped into the cavitys, from outside the house by drilling few holesetc.
If you require any more information dont hesitate to ask.

Mellor

tobinj6 wrote: »

now i assume that the 5m * 4m is very valuable space and you dont wanna lose all that much so the foil back board option will suit you better.

How would the foiled back plasterboard affect the amount of spae lost??

ircoha

If the construct is cavity BLOCK then pumping is not really an option.

If cavity WALL then while pumping is a theoretical option, IMO the internal insulation approach is best, loads of different combinations thrashed out here on the forum.

In passing, while not in the OP's question he should consider moving away from flat roof if possible

muffler

ircoha wrote: »

In passing, while not in the OP's question he should consider moving away from flat roof if possible

That indeed would be a good recommendation. May cost a few quid more but it will save money in the long term.

sinnerboy

be carefull installing insulation in between your flat roof timbers. you HAVE to ventilate those timbers if you do this . easier said than done in a lot of cases .

IF a pitched roof is not an option - then insulate OVER the existing roof covering as part as a multi layered torch on felt roofing system - no need to vent then . and it is better if existing plasterboard is NOT foil backed in this set up. A not inconsiderable advantage is minimal disruption and mess internally .

I can PM you a very good contact if this is of interest

sinnerboy

forgot - walls

dry line these - 50 pu boards on timber battens . foil tape the joints and plasterboard over .

best if you can extend the PU boards up past your ceiling right up to the underside of your roof deck .

you may have to lose and replace your ceiling to do this . a crafty tradesman MAY be able to remove only the amount of ceiling required ( 75mm strip )

sinnerboy

Mellor wrote: »

How would the foiled back plasterboard affect the amount of spae lost??

IF headroom is bang on 2400 min - then CPB on ceiling would spoil this .....

On walls foil backed only will do next to nothing for insulation - you must accept 75mm loss of space for improved insulation

Mellor

That was my point SB, the first reply suggested that somehow that foil backed plasterboard reduced space lost (by improving insulation). Its a common misconception that the foil back plaster board has some insulation properties.

tobinj6

hi i think my advice in full was taken out of context as i didnt word it right what i meantby space was not to batten at all and just foil back board but worded wrong and i apologise for that

chopra33

i had same problem and got rid of flat roof,guys put on slate roof and walls and roof insulated.it was well worth it and made a great diff,hav number if u want it.