30 to 50 years is not an unusual lifespan for green roofs in europe.
Green roof lifespan.
As a result the roof structure can require less maintenance saving the owner money in replacement costs over the long term life of the roofing system.
How long will my roof last with a green roof.
A green roof can increase the life expectancy of a roofing system by protecting the roofing materials from direct ultra violet radiation and extreme temperatures.
Green roofing can extend the lifespan of a roof by over 200 by covering the waterproofing membrane with growing medium and vegetation this shields the membrane from ultra violet radiation and physical damage.
Irrigation wastes water and energy both are what the green roof should be conserving.