6 questions to ask before signing the dotted line for a green roof!

With another green roof installation season just around the corner (yes, it is almost March!!!), I thought I would do a brief post on what I would ask (and hopefully you too) before saying "YES!" (because you're going to say it with great gusto, right?) to a green roof...

-What's going to be in the medium mix? This is an especially important question if you (or "the client", if you are representing someone else) has qualms with materials like peat moss or coir, for instance.

-Has the medium been tested by a third party? The medium is obviously key to the success of a green roof or green wall and you want to know someone else, objective, can verify its bulk density, water holding capacity and more. If you're not sure all of the parameters to ask about, find someone objective who can help you out.

-What kinds of plants will you be using and why? This will alert you to how much the designer has thought about the design for the rooftop. Is the designer just going with what is considered to be the standard...or what they always used/recommended in the past? Are there other plants you could try which you might like more in terms of aesthetics or biodiversity?

-Have you done an installation before? In parts of North America green roofs are still new and an experienced installer may not be available. The job could be done effectively if the prospective installer has thought about how to get it done or has someone with building experience to help out.

-What are my options for waterproofing membrane testing? You obviously want to make sure that this wonderful new green roof which is going up won't have to be taken apart or taken off entirely in just a few years because the waterproofing membrane was on its way out and needed to be repaired or replaced. There's a few of tests out there, some more reliable, others more expensive.

Here are the choices:

a. EFVM (Electric Field Vector Mapping)
b. Flood Testing
c. Capacitance Testing
d. Infrared Thermal Imaging
e. Low Voltage Testing
f. Nuclear Testing

-Is a thorough clean-up included in the quote? By this I mean not only removal of all containers, leftovers and debris, but if a little medium blows onto a neighbors property, will the installers be so kind as to take care of that too to keep the peace?