EPS Insulation on a New Flat Roof.

[Paul35]

I have just had a new flat roof after 38 years and due to many leaks in the ceiling, I am now looking to re-insulate with new plasterboard on top.

I currently have rock wool (which is 38 years old) with no vapour barrier under the plasterboard.

My flat roof holds my Kitchen, a small passage area, and my bathroom and due to many leaks in the ceilings, I will need to re-plaster and insulate from scratch.

I would like some advise on weather on not to get rid of the old Rock Wool and replace it with some 75mm or 100mm Polystyrene Boards?

I currently have no Vapour Barrier and would like to install one. Is this a good thing? Could I do without it? If I do go ahead, I would go with a 300ga one. Not sure if that's good or not?

Thanks in advance.

 

[vinn]

Your last post proposing this roof made some claims for having the job done in one day.
I wonder how this new roof was constructed?
Do you have photos - esp. at the chimney stack and fascia areas?
Is it a warm roof or a cold roof?

 

[Paul35]

My New Roof was done in a day and a half in the end! First day 10am to 6pm, second day 9am to 11am.

Is it a cold roof.

Have enclosed some photos.......... and would give the roof a 6/10!

 

[chappers]

yep you have a cold roof and as such should really be ventilated to the outside over your insulation.
100mm celotex between and 50mm under the rafters would be close to regs or200mm between. though what you are proposing would almost certainly be an improvement on the existing.
If there is no ventilation, then introducing some might be difficult now your roof is finished and if this is the case then I would definitely include a VCL