It is always best when buying a shed for this purpose to go for a reinforced shed.
Green roof system for shed.
Building a green roof on your shed is a way to add interest to the shed and produce a new area to cultivate.
Green roof installation guide.
For a green roof installation that pitch should be at least inch per foot of run.
Step 1 check if it is load bearing.
Check that your shed is strong enough to take such weight and remember that the walls will also play a large part in bearing the load.
When fitting a green roof to a shed make sure that your shed roof can take the increased weight load from a green roof.
And also so you can find out what works for you.
Alternatively you can reinforce and brace the internal shed structure and roofing joists before fitting.
There are some things you need to check before building but the job is not very difficult.
Before the plants go up a structural engineer should check to ensure that the roof can support the weight of the engineered growing medium and plants.
You will also need to make sure that your shed s roof is waterproof.
Green roofs are made up of several layers typically a waterproof root barrier layer to protect the roof a drainage layer water retention mat then the growing medium and vegetation.
For this shed i used 3x2 softwood timbers at 600mm 2 ctrs which spanned 1 2m 4 with an 18mm 3 4 plywood deck.
For plants to flourish on a green roof they will need moisture and drainage which means soil and a sturdy framework to keep it in place.
Even a flat roof should have some pitch so that it sheds water toward gutters.