There are a lot of reasons to opt for a flat roof construction for your building project, from increased usable space, the potential for roof storage and the relative inexpensive of repairs, as well as flat roofs simply being in architectural vogue.

However, one of the most fascinating developments over the past decade is the potential for the green roof, where a roof is used as a bed for plants, grass and shrubbery.

It does not necessarily have to be flat, but flat roofs are far better suited for housing plants, and a specialist can help with ensuring that the roof is structurally secure enough.

However, a new concept known as a blue-green roof is becoming increasingly popular in Amsterdam through projects such as the Resilience Network of Smart Innovative Climate-adaptive Rooftops (RESILIO).

This combines the beauty and sustainability found in a green roof with the water retention and storage of a blue roof, something that has been seen since the “sponge city” concept of the 2000s where green infrastructure is used to reduce the risk of flood damage and the strain of urban drainage.

It takes the concept of a green roof further; whilst greenery will naturally absorb water as part of their living processes, a blue-green roof uses a layered system of water retention and recovery. 

The RESILIO system uses a layered roof system that has the plants and soil on the top layer, a filter layer to keep soil and plant roots from reaching the roof and a crate system that absorbs, stores and filters the water into water storage systems.

There are even experiments into having a layer of solar panels, allowing a green roof to be used for power generation at the same time.

The problem, and a reason why a blue-green roof is not an adaptation everyone can use is weight; whilst the greenery and even the soil are not too heavy, the water being stored is, and this needs to be accommodated into retrofits.