Shipping containers are enablers of globalisation- they secure and deliver the goods people want and after their travels are over are still good for storage, and sometimes living in.

But once the roof of a shipping container starts rotting it is the beginning of the end- if water gets into the container it is soon rotten and useless for anything but scrap. So you can put a new roof over the top and extend its life by 20-30 years, maybe more. The best way of fixing a roof using wood is to bolt lengths of wood along the length of the container. There are two roughly 50mm square beams that run the length of the container to which 75x50 wooden beams can be bolted. The 50mm metal beams are not flat on the top- there is a weld along their length where a roof plate is welded onto them which raises the inner side of the beam about 5mm. So it is best to cut into/rebate the wooden beams lengthwise about 5mm and about 30mm across- a circular saw can do this accurately enough. At the ends you need to cut out more to allow for the 150mm corner posts. It may also be necessary to increase the depth of the rebate as you approach the posts...there may be additional welded plate there.

Use 4 or 5 8 mm or 10mm coach bolts to fix the wooden beams to the metal beams.

You can build a sloping lean to roof or a slightly curved roof by fixing lengthwise beams between the two sides to provide the slope you want. With a curved roof you only want about 50mm difference between the two side beams and the centre beam.

Lean to roof-

Curved roof