How do I recognise condensation .

[sliktor]

i have a number of white steaks on the rafters in my loft.
how do i recognise whether there is significant condensation before i have the cavity walls filled?
at present i have about 100mm of insulation only.

 

[Deluks]

Moisture in the roofspace is usually ingress from outside :ie: Rain!

Can you take a picture? White streaks could be dry rot.
Is your roof felted under the tiles? Any damaged/missing tiles?

 

[sliktor]

thanks for your reply.

will try to take picture.

No felt under tiles.