Flat roof insulation

jmlong · 30 Aug 2009

Hi there, I have a ground floor bathroom with a flat roof I was wondering what is the best type of insulation for this type of roof. Can you have the blown in type or are rigid boards better?

Just to let you know I am not re-newing the roof and plan to install insulation by removing the weather board from one side.

Cheers

noseall · 30 Aug 2009

And what happens if you discover mid-span solid bracing or noggins?

jmlong · 6 Sep 2009

And I've thought of another problem it seems the roofing material is bonded to the weather board therefore I can't remove the board without risking damage to the roof material. Any ideas or advice greatly appreciated. I realise that replacing the flat roof with a pitched roof and proper insulation is the ideal solution but at the moment funds don't allow.

Deluks · 6 Sep 2009

jmlong said:
replacing the flat roof with a pitched roof and proper insulation is the ideal solution

Not if it isn't leaking, no need. You can rip down the ceilings and install insulation/vapour barrier from inside the room. Plasterboard is cheap to replace, and you'll probably get a local plasterer do skim it for a one-er (one hundred pounds sterling)

PerryOne · 8 Sep 2009

Pull the ceiling down and fit at least three inch thick polystyrene in between the joists as a tight friction fit, taking care to leave no holes.
Then fit another layer of two inch thick polystyrene under the joists and finish with plaster board. As its only a small room plaster the ceiling yourself its really quite easy.
The two inch thick polystyrene under the joists is required because the joists become the weak link and if you do not do this then ghosting will appear, ghosting is where the water vapour in the air (and there's a lot in a bathroom) will condense on the plasterboard in lines where the cold joists are leaving two inch wide lines across the ceiling.

noseall · 8 Sep 2009

PerryOne said:
Pull the ceiling down and fit at least three inch thick polystyrene in between the joists as a tight friction fit, taking care to leave no holes.
Then fit another layer of two inch thick polystyrene under the joists and finish with plaster board. As its only a small room plaster the ceiling yourself its really quite easy.

This method would not satisfy reg's and would only be considered an improvement.

For best results use foam board, i.e. celotex or kingspan. Current reg's are asking for minimum 125mm of foam board - either above, between or under depending upon design (warm or cold deck).

PerryOne · 8 Sep 2009

three inches and two inches = 5 inches = 125mm
Celotex and Kingspan are trade names for polystyrene they are all closed cell insulation.

noseall · 8 Sep 2009

PerryOne said:
three inches and two inches = 5 inches = 125mm
Celotex and Kingspan are trade names for polystyrene they are all closed cell insulation.

For your information, polystyrene and pur/pir board are very different as far as the building trade goes, both in performance and price.

You need to update your terminology dear boy.

ColJack · 8 Sep 2009

PIR = PolyIsocyanurate Rigid insulation..
PUR = PolyUrethane Rigid insulation..

freddiemercurystwin · 8 Sep 2009

PerryOne said:
Celotex and Kingspan are trade names for polystyrene

Try getting that notion past building control!

dextrous · 8 Sep 2009

polystyrene burns better though

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Flat roof insulation

dextrous

Similar threads