30 to 50 years is not an unusual lifespan for green roofs in europe.
Green roof lifespan.
A properly installed and maintained green roof should extend the life of the roof 2 3 times its normal life.
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.
By protecting the roof membrane however a green roof can extend the life of a roof by two or three times beyond its typical lifespan.