I Have Discovered My Caravan Is Damp

[newcastle1]

I have taken my caravan for a service and they are saying it is really damp. I am completely gutted as to me it looks in good condition. Some areas are 'spongy'.
Just wondering how meter reading for damp is done and if I can dry the caravan out.
Anyone any idea about this, please?
Thanks

[davebro]

You can get de-humidifiers but as it's damp it probably means water is getting in somewhere so that needs to be found and sealed. Is it old? - not that it matters much. My mate bought a new van that had to go back to the factory to have leaks dealt with.

[newcastle1]

It is about 10 years old and was covered but in a massive storm the cover got damaged so it has been outside for 6 months with no cover. I believe that I know where water is coming in so need to seal around these areas. Also, caravan has quite a few 'hairline' cracks so not sure how to address these. I think the water ingress didn't help as it was quite green so my nephew power washed it, which I am sure added to the problem.