Hi Gerry, I am starting to put together a few ideas for our roofgarden/balcony area and hope to start as soon as possible. I read somewhere that it is best to use an extra special lightweight soil. I have tried to find it in some garden centres or on the internet and no such luck. Any idea where I might be able to source this product or what do you recommend for this situation.
The concern is about safe load-bearing. You should check with the builder/engineer how much weight can be safely added. It may not be necessary to use lightweight compost or limited volumes.
Perlite and vermiculite are lightweight additives with peat and some soil.