ABOUT GREEN ROOFS - FAQS
How much do they weigh?
Minimum 21 lb/s.f. additional dead load. Rule of thumb is each inch of growing media adds 7 lb/s.f.. ASTM standards E2397 and E2399 govern determining dead load of green roofs.
Are leaks a problem?
Leaks are issues on most roofs without green roofs, which is why we recommend electronic leak detection to ensure the membrane and flashings are leakproof prior to green roof installation. Electronic leak detection can also be used later to find a leak and vegetation can be easily removed locally for a repair.
How much do they cost?
Costs can vary greatly based on size of project, roof accessibility, type of green roof (media depth, plants, etc) and design features of intensive roofs. For rough budgeting, they can range from ~$8 to $25+ per square foot.
Are there standards?
Yes – green roofs have been common practice in Germany, Japan and other countries for many years. German FLL standards for growing media contain detailed criteria for weight, permeability, nutrient content, etc. The American Standard Testing Methods (ASTM) has and continues to develop green roof standards.
Can they be used with solar?
Yes – vegetated roofs are complementary to any PV system as PV operates most efficiently at the temperatures a vegetated roof generates on a hot day (~80 deg F).
Can I put a green roof on my existing roof?
Yes; however, you need to ensure it can handle the additional dead load and you will not get all the benefits of a longer lasting membrane. It is recommended to install a green roof at the time of a roof replacement.
Is irrigation required?
This depends on the type of plants and system you design and your specific climate. The most functional, extensive system will likely not require irrigation. If it is necessary, we can install subsurface irrigation.
Are all designs created equal?
No, your roof should have an experienced designer/installer work with you based on your specific climate, plants, roof features, and project goals/expectations. No one system can be used even in one climate zone.