Dry Lining and Insulating Concrete Roof

[Graham]

Live in top floor flat. Roof deck is made of 6" concrete with 1" polystyrene insulation with screed and asphalt on top of that. Very cold in winter, much condensation. Summer very hot night time. Want to insulate on inside as we suspect the polystyrene is partially missing when re-asphalted a few years back.

Next door neighbour, same problem, has been quoted to supply and install a MF ceiling grid, 50-70 mm rockwool insulation, 12.5 mm plasterboard, tape and joint ready for painting.

No mention of vapour barrier in quote !!

Questions/help needed.

1.

[Graham]

Live in top floor flat. Roof deck is made of 6" concrete with 1" polystyrene insulation with screed and asphalt on top of that. Very cold in winter, much condensation. Summer very hot night time. Want to insulate on inside as we suspect the polystyrene is partially missing when re-asphalted a few years back.

Next door neighbour, same problem, has been quoted to supply and install a MF ceiling grid, 50-70 mm rockwool insulation, 12.5 mm plasterboard, tape and joint ready for painting.

No mention of vapour barrier in quote !!

Questions/help needed.

1.If do get vapour barrier installed, the roof in my opinion would then get even colder in winter and might make condensation form on the existing ceiling which could then drip spoiling ceiling paintwork.

1. There is no thought given to ventilating the void, if were feasable.

2. Presume water vapour, over time, would work its way in between the new insulation and the concrete roof deck ?

4.

[Graham]

Live in top floor flat. Roof deck is made of 6" concrete with 1" polystyrene insulation with screed and asphalt on top of that. Very cold in winter, much condensation. Summer very hot night time. Want to insulate on inside as we suspect the polystyrene is partially missing when re-asphalted a few years back.

Next door neighbour, same problem, has been quoted to supply and install a MF ceiling grid, 50-70 mm rockwool insulation, 12.5 mm plasterboard, tape and joint ready for painting.

No mention of vapour barrier in quote !!

Questions/help needed.

1.If do get vapour barrier installed, the roof in my opinion would then get even colder in winter and might make condensation form on the existing ceiling which could then drip spoiling ceiling paintwork.

1. There is no thought given to ventilating the void, if were feasable.

2. Presume water vapour, over time, would work its way in between the new insulation and the concrete roof deck ?

4.What is the ideal way to rectify the bad situation other than putting new insulation on top of the asphalt.?

Thanks for any help, and apologies if this message got posted before finished.

[Rick]

One easy way is to use insulated plasterboard stuck to the ceiling. It comes quite thick. WIll be an real bitch of a job to stick it up.

I have insulated celings from the inside, I put up a pile of celotex/ kingspan, then a studwork to attach the plasterboard to. You seal the celotex joins and edges with expanding foam, its pretty much watertight in its self anyways. You can the additionally add rockwall into the studwork. I'd go for 100mm of kingspan, and then 75mm of rockwall in the studwork.

If the roof leaks, the new ceiling will need to come down, but I assume you have the roof maintance done well.

Rick