Roof Cleaning Advice Needed

[toad a caravan]

I cleaned this roof using the method I used in my previous post on Oct 24..Gary

 

[Dustydog]

A lot of elbow grease👍👏

 

[toad a caravan]

Yes but not to much effort all at once,this is the second one I've done recently,my own and my cousin's,on my own I split the roof into four separate sections on his into eight,due to the different size of roofs,this I found the easiest,I used a soft nylon sweeping brush and a light pressure after applying blaze cleaning fluid,then hosed it of,until a decent finish,,the power washer stayed in the shed.

 

[Beachball]

Looks stunning what a great job you have done

 

[otherclive]

Looks fantastic but I don’t think I’ve seen one so bad. Mine would go October to end of March unwashed but I did use Fenwicks Overwintering fluid.

What causes yours to degrade that badly?