We have a cover that covers the front, roof and back of the van, from Specialised Covers. They're make and model specific, to fit over the sunroof, aerial etc and can be customised if you have a solar panel you want to keep using or an aircon unit etc. We got a small discount using a code from an advert in the C&M Club (I think!) magazine.
It needs to be fitted onto a dry van and is a bit fiddly to fit unless you've got plenty of room all around the van. It's really a 2 person job and we need a small stepladder to reach the track along the roof. The cover is surprisingly lightweight, which helps. The online video showing how to fit and remove it is extremely useful.
The cover definitely does what it says and protects the parts of the van it covers from dirt, leaves, seagulls etc. removing the need to wash the roof especially after standing over winter.
Not a cheap purchase but worth it for us to remove the hassle of cleaning the roof and the back of the caravan which get particularly dirty where we keep it.
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