Green roof

3 options

soil is heavy, A sedum roof however, made with sedum matting, is reasonably light weight
consider 1 or 2 planters on the side, to keep weight low. instead of planters everywhere
create a very sturdy bin roof. that can support lots of soil.

Sedum doesn’t enjoy shade. if i plant a tree that might be an issue.

bluum recommends:

sedum
succulents kit
- Never, ever use multi-purpose compost. John Innes no 3 is ideal , but no 2 will suffice.
- Mix a free draining element into your soil before planting. This can be horticultural grit, gravel or perlite.
- Increase the ratio of the perlite/grit/gravel if your area has a wetter climate. Up to 80% drainage
alpine plants
wildflowers
grasses
herbs