"New" fibreglass shed flat roof already leaking within 3 months

[JP_]

I guess so, your need to build a frame for a fall with ply on top, and covered. Basically building a roof!

 

[datarebal]

Regardless of the ponding it should not leak.

Check the condensation test then decide

 

[^woody^]

The droplets suggest condensation, but the excessive joist staining not, and the ponding suggests it's not leaking!

Did it get condensation before?

Either way that amount of moisture whatever the cause is not going to be good for the OSB deck.

 

[catlad]

Looks like there is a wall missing because you can't build off a single joist like that and not expect it to sag. You should have a jack in your car so then get a length of timber 4x2 or similar. or just hire an accro prop from a hire place.

 

[Bullet-Proof_Biscuit]

Long shot but is there any mileage in jacking each joist in turn at the hanger and fitting packers just enough to cause a fall to one corner. Come to think of it, there is no drain gulley or gutter?