Flat roof condensation

[joejoiner]

I have recently built an extension.
Due to roof on original I have had to put the top section of the new roof in a flat roof.
I used a single ply membrane. It was completed around two months ago and already all the ply on the underside is covered in mould.
im fairly sure there is no leak and think its condensation. i have continuos ventilation in the soffit. will high level vents help??
Thanks

 

[freddiemercurystwin]

Due to roof on original I have had to put the top section of the new roof in a flat roof.
Is

I have no idea what any of that means.

 

[joejoiner]

I mean the original roof has rosemary roof tiles and due to height restrictions with the hips my new extension had to have a significant top section which is a flat roof.
I would appreciate some advice on the damp/mould issue.
will vents higher up, ie above the insulation help?
I'm very concerned at the state of the plywood already.

 

[Alastairreid]

Cold roof?

https://www.youtube.com/watch?v=TpqgM-jxVAU

 

[freddiemercurystwin]

Nah still don't get it, oh well someone else can fathom it out.

 

[noseall]

Nah still don't get it, oh well someone else can fathom it out.

He intends building a 'flat topper'.

We have built two in the last 6 years the most recent was built last autumn. It is when a hipped roof maxes out height wise and reverts to a flatty in order to not exceed a given height.

Architects and builders always opt for a warm roof deck for obvious reasons.

 

[freddiemercurystwin]

Yep I get that bit but don't understand how he's gone about detailing/venting it and until that's clarified the thread is going nowhere.