It takes a long time to put together and is definitely fiddly at points. You cannot do this on your own - for a while there were 3 of us working on this, although the roof was done with 2 the next day. There are an awful lot of screws to put in and quite often the drill wouldn’t do it so a hand screwdriver needed to be used, at least to start them off or tighten them at the end. The screws that have to go through metal are particularly tricky.
My main tip for anyone would be when you think a piece is pushed in all the way, use a block of scrap wood and firmly knock it with a hammer/mallet - I found out the hard way that pieces weren’t flush even when you thought they were without doing this! However all the pieces are clearly labelled so it’s easy to be sure you’re working with the right part and fixings at any time, including labels which show way up pieces should be.
The size is good so it’s really useful for storing lots in an organised way, I’ve been able to put up 2 large shelving units inside and still have lots of floor space for other things. If you’re careful everything fits together well. The tolerances are very small so you do need to be precise and careful with the pieces. Considering how light and even flimsy the plastic pieces feel when you take them out of the box, when it’s all together it feels very sturdy and the plastic material feels durable, including the roof.
I can’t comment on waterproofing yet as it rained while putting it together but not since the roof went on (typical) but there’s nothing that makes me think there will be an issue.