This cold weather has really shown up a problem with an unheated converted
agricultural implement shed. The building is used to store generators,
lights and small tools and has had a plasterboard ceiling added, to stop
dust and bird crap spoiling the kit.

The gable ends are ventilated and the roof is simple 4 by 2 rafters with
corrugated iron, the corrugations vent at the eaves and the ridge capping.

This roof is plainly a good radiator on cold nights and vapour from ambient
air is condensing, and sometimes freezing, on the inside then dripping onto
the plasterboard below.

I'm considering stapling tyvek in between the rafters or even full length
under them but worry about the effect this will have on old untreated roof
timbers?

AJH