I'll have to go out and have a better look when it's light again, but I think mostly the tops of some of the planks have fallen away - but last time I looked, I think the wood felt soft and crumbly in places. If you're thinking is it repairable, hhmmm, maybe I should inspect it better... but certainly the paint is flaking off everywhere, so if I set out to replace some timbers, and paint everything else, I think it would be a hell of a job to scrape all the old paint off - let's see - 25 x 2 x 5 = 250 strips of woodYou said crumbling.
Do you mean rot? What part?