Challenges and constraints

Maintenance

All roofs need to be maintained.
Extensive green roofs need an annual inspection to ensure all drainage outlets and shingle perimeters are vegetation free.
Green roof vegetation will need additional low maintenance, depending on the system.
Intensive and semi-intensive green roofs will need irrigation and a higher level of maintenance. They are, after all, parks and gardens!

Green roofs will mean an uplift in structure to support the green roof. However, this uplift should be balanced against the benefits the system provides to the building and the wider environment.

Green roofs do cost more but this cost can be offset through reduced ground-level water storage devices, increased property value and energy savings.

Green roofs are seen to be more of a fire risk than more conventional roof solutions. However, in Germany a building with a green roof will get a reduction in the cost of fire insurance as the green roof protects the waterproofing from fire.
Green roofs systems that are approved by the German Green Roof Guidance Board follow very strict rules regarding the amount of combustible material and the need for firebreaks.
There have been no major incidents of fire in the German and Swiss markets, where over 75 million m² of green roofs have been installed.
A picture of a green roof fire break can be seen on the right.

Green roofs do not cause roofs to leak. Only poor installation can cause leaks (most good companies leak test before installing the green element).
In fact, the main advantage of a green roof is that it protects the membrane from damage, thus extending its life.
There are examples of green roofs in Germany and Switzerland where the waterproofing has not been renewed even after 90 years.