Any builders/roofers out there?

[gumby6371]

I've got a shed at the bottom of my garden with a tin roof that suffers badly with condensation, when I say shed it's single skin brick walls 3.5 by 4 metres.
Looked into reroofing costs and with it being rented it's not worth it, tried fixing heavy grade polythene to the underside of the rafters as a moisture barrier which helped but hasn't cured it.
Now wondering if I could take the corrugated sheets off, fit a layer of roofing felt to the top of the rafters and refit the sheets on top.
It's heavy grade 'square' corrugated steel if you get what I mean so there would be large ventilation channels between the felt and the tin and the felt and the polythene would affectively turn the rafters into a cavity.....I think.
Would this work?? I'm getting fed up of having to cover everything I keep in there with polythene to stop it rusting, it's like standing in a rain shower some days!

Cheers
Gareth

[lozz]

felting it shouid keep the dampness out,
ithink your on the right path with your idea,

[gumby6371]

Cheers for the response Lozz, I'll wait for a dry day and another pair of hands to help.

[lozz]

You always get condensation off tin roofs,

there is a special paint you can apply it sets hard like rubber,
we use it on flat roofs over shops normaly cures it,