The roof on the old van has not been cleaned for years. A decent layer of algae and general muck on there. Was advised to use a warm soapy, bleachy, solution and a long handled brush.
It worked on the sides and back, however I am a bit concerned what the bleach would do to the seals if anything?
Fenwick's Caravan Cleaner is the product you need. Just dilute as directed on the container. It shifts stubborn algea and any green stains left behind but you may have to work it in with a soft paint brush especially around the awning rails and trim. It works well on my caravan and use it just once a year for this purpose, the rest of the time I just use a dry wash cleaner such as Showroom Shine as this shifts the black streaks that form below service doors and windows.
As said previous, avoid using bleach at all costs as it will do more harm than good. It's okay for cleaning out smelly pipes and grime etc, but not for cleaning caravan surfaces as it could do damage to the decalls.
I demonstrated it on really bad green algae on this 30 year old van Im working on and the owner was impressed with the results, saying he'd spent hours getting the van as good as it was with huge amounts of effort and was amazed that this concentration just swooped it all off with very gentle persuasion from a very soft brush.
He'd bought the Fenwicks caravan remover but not read the instructions to dilute it 10 to 1 for black streaks and stubborn grime.
The impact was really significant for very little effort and most of it just rinsed away.
------------- Green cleaning in North Yorkshire & Teesside inc Caravans from 2014