damp patches inside new garage roof ?

I recently replaced an asbestos garage roof with the same profile in cement fibre and, though there are no leaks as such, some damp seems to be penetrating in a few areas not necessarily where the holes have been made for the bolts to secure the roof. I have added further sealant but not sure what else to do to rectify. Appreciate any advice
please.
Pete

Pete
November 2009