Condensation forming on roof and back wall

[PaulJones1980]

Hi All.
I a am having a serious problem with condensation up stairs in my house.
We are doing a renovation.
it is solid block construction with a flat roof.
the whole house has been taken back to blocks and re packed every joint wrapped in expanding metal and rendered,
The roof was rotten due to water ingress so has been completely replaced with new timbers and felt it had a breathable layer of felt added.
Noticed the condensation but put it down to the fact we had been plastering and the amount of water was the problem.
we have since had 5 mushroom vents put in the roof and the problem is still there. I am convinced its because the back wall never gets sun and is a cold wall but the roof gets hammered and gets very warm. Please help me i am tearing my hair out and need some answer

 

[PaulJones1980]

I have Just Spoke to a Local Damp expert and he has told me it will be due to the fact that we have plastered the whole house inside.
We used sulfa-crete wit a trimix water proofer but nothing has been laid on now in over 3 weeks does anyone think this is a possibility?

 

[^woody^]

Vents to a roof space will do nothing to stop a condensation problem in the rooms below.

Also, unless the roof was insulted at ceiling level when replaced, then it could potentially be a condensation problem in the future

And I can't see how you have had a breathable membrane fitted to a flat roof

You may need to turn the heating up or hire a dehumidifier to dry the place out. But if there are cold walls and ceilings, then they will always be prone to condensation so you will have to deal with that via the normal methods

 

[foxhole]

With recent bad weather the drying process will be severely retarded, you will need windows open as long as possible to promote drying. You should also ensure all wall vents are clear and have not been blocked during the render process. Do you have vents to each room?
Local damp expert ? a surveyor or other qualified person?, or someone selling damp proofing?