I have a new question. It relates more to roofs than it does to gardens. Has anyone had any experiences with the safety of roofs - and their care - while creating a garden on top of one? I recently noticed some fluid trapped between the membrane and the material below it. I am working within the structure of a large non-profit organization, and I am doing my best to ensure the safety of the roof while creating the garden upon it.

I have a few heavy plastic containers and a bunch of lighter windowboxes there. We must walk on the roof extensively to do regular gardening tasks. The roof has been prepared by a professional company. Supposedly it is a "high class job!"

Any ideas so far? Thanks, Steve

We have similar concerns here: our roof is fairly new as well, and of course, we do not want to damage it.

Do you have your containers directly on the roof or do you have a deck installed?

The fluid under the membrane would worry me. If the roof was done by a pro company they often give warranties on roofs (10 years or so). However, extensive walking on the roof would probably void that warranty. Any way, I would look into that first.

I am sure some experienced handy people will have some insight, but my guess is that the membrane got punctured somehow and that's how the fluid got trapped. It shouldn't be too hard to fix that, but my main concern would be how to avoid it in the future.

Anyway, I have not been very helpful, but I am very interested and would like to learn more about your set-up.

http://www.alternatives.ca/article1165.html

This document about the same projet is in french but contains many pictures. Isn't a picture worth a lot of words? :)
http://www.alternatives.ca/IMG/doc/Jardins_hydro.doc