Bitumen, Thompson 10 year roof seal or something else to replace old fiberglass flat roof

[bigjimmi]

Hi, DIY noob here, we've just moved house and I now have a double external garage with a flat fibreglass roof that looks like it's letting water in. It's not dripping in or leaking, but there's black patches on the boards after it rains and signs of some mould on the boards underneath. I don't want it to get worse this winter as it's going to be a few years before I can look to replace it or do anything major with it. So I'm exploring DIY options...

I've watched a few youtube videos etc and seem to have narrowed it down to either a multi coat Bitumen paint with scrim or something like Thompsons 10 year roof seal, which says it out performs Bitumen etc.

Has anyone any advice which to go with? Is there any issue with putting Bitumen over fibreglass?

Thanks in advance!

 

[^woody^]

Acrylpol

 

[bigjimmi]

Any reason you favour Acrypol over Bitument?

Any issues with using Acrypol on a fiberglass flat roof?

Thanks

 

[Diver Fred]

Bitumen over fibreglass is very likely to cause the fibreglass to breakup - it will absorb heat from sunlight and cause the fibreglass to expand more than it does already. A light coloured Acropol or similar will reflect sunlight and so not expand as much or as quick.
Put a good thick coat of Acrypol on the existing roof.