So we have quotes in from two of the leading providers in the US. The benefits of their systems include pre-grown trays with soil preparations and adjustments already set for your growing zone. Essentially it is like buying "sod" for your roof versus planting from seeds. The cost is the largest hurdle, coming in at over $25 a square foot in most cases. So our little project of 500 square feet was easily coming to over $10,000.
Continued research led us to a very cool company called Geoproducts Corporation. They make an incredible amount of products for construction, irrigation, and general building. Their outdoor section is here
. They offer a Geodrein tray that is made from recycled plastic and is ready to install on a properly waterproofed roof. You snap the trays together, add a volcanic or pumice material for drainage, cover that with a geotextile that separates the roots above from the drainage material below, add your soil or growing material, and finally your plugs/plants.
The best news? The trays are $2.08 per square foot plus shipping. We are now looking to price out the other raw materials to see if we can save money with this approach. More to follow.