Before tackling the inside find out where the water is getting in on the roof. Look for perished sealing putty.
Once the source is found and dealt with you can then concentrate on the inside, if you don't do this first you'll be 'flogging a dead horse'.
Spit the blisters but have a bucket ready there may be a water fall leave splits open or cut around the bubble. Put heater on to assist drying out and place step ladder in the caravan under the bubbles and stand moisture absorber packs on the step ladder by sound of it you'll need at least six this will absorb moisture emission from the roof as well as in the air in the c/van. I use them for over winter storage moisture collectors.
Think of replacing cutting out the damaged section back to roof frame and fixing blocks to the framing to fix the new panel section allow a small gap all around the panel so you can fix with a good adhesive plastic joint strips you should be able to get the panel, joint strips and adhesives as well as the roof sealant from a C/v service centre. Don' forget the edges of the roof check everywhere their is a strip or sealant joint on the roof.
bob, March 2014
