If you are considering a container conversion then some kind of roof form must be considered as the shipping containers themselves are finished with corrugated steel which if left as a final finish will act to collect and pool water rather than drain it in any way.
For a basic conversion there are a couple of options;
The majority of shipping container conversions I have seen to date have been constructed with a flat roof profile using the existing structure as a base for insulation and a finished surface that suits the project.
The expected loads on the roof are a major consideration, as shipping containers have general load bearing tolerances, but these can be significantly reduced once sections of the containers walls are removed, or if internal bracing is removed for aesthetic reasons.
A green roof has a certain ‘dead load’ in the weight of the growing medium (soil or similar) as well the plants, and the water that the structure holds at any given time. This may indeed require extra steel supports in the roof structure.
The services of an architect or structural engineer will be needed to help you calculate the loading and any supportive structures, as well as the design details that are required for the proposed roof structure.
The poor insulation qualities of raw shipping containers also influence the amount of insulation that goes into the roof structure and whether it fits within or on the outside of the structure.
An earth roof generally has high insulation qualities due to the thickness of the growing medium, but extra insulation can be added.
To learn more about insulation you need a basic understanding of R and U values and the differing R values that different materials have.
Ultimately the roofing option that you choose will depend upon the visual qualities that you are looking for, your budget, site profile and the dominance (or lack of) the roofing structure will have on the finished project.
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