about a pitched roof?

Take note of Peccavi and also in addition check the ventilation at the eaves these should be kept clear of insulation to allow venting of the roof space.

bob
January 2013

What can you do?

Find the cause and rectify it...
I would guess one of:

Water ingress through roof.
Leaking water pipe in loft.
Condensation dripping onto trusses from above.

The pattern of wetness you describe tends to suggest the condensation theory.

My guess is that you're somehow allowing warm, wet air into the loft space - does a bathroom ventilator pass through the loft space?

Peccavi
January 2013