bailey alu tech

Good afternoon, I've recently noticed, after taking the van out of storage, black spots and pimples, in front of the hot water tank and spreading aft under the bottom bunk bed. this is only in spots and not extending from the sides. I've checked the underside of the floor, with damp readings...

I've been hearing that the Bailey Alu-Tech caravans have a tendency to let water seep through. Is this true? I would have thought that since they use fewer panels, they would be much better at preventing water ingress. Does this also mean that the Alu-Tech caravans also get a lot of damp? I can...