Though experiencing a surge in popularity, living roofs are by no means a modern phenomenon. We know that green roofs date back beyond even the Vikings who built entire villages of living roofed houses.
One of the oldest living roofs is to be found in Lucca, Italy where a 14th century tower stands with a small collection of oak trees sprouting from the top, but the earliest examples of buildings completely topped with the sort of low level vegetation we would usually think of as a living roof today originate from Northern Scandinavia.
Copywrite Glen Bowman, Flikr
The original purpose of turf roofs
Sod roofs were essential for the construction of the type of rural log houses which were built in this cold region. The primary purpose of the soil and turf placed on the top of these buildings was to hold in position the layers of birch bark used to waterproof the cabins.
Norwegian log cabin with traditional sod roof
Copywrite Roger W Flikr
An additional benefit was the weight which the six inches of soil and sod provided on top of the structure. This weight – usually around 250kg per square metre, and even more under the winter snow – compressed the logs used for the walls of the cabins together making the house sturdier and preventing draughts through gaps in the wood.
As with modern living roofs, sod roofs provided good insulation through cold Scandinavian winters.
Competion from new building materials
As new building materials became available in the 19th century, construction methods changed and so the numbers of green roofs, used for hundreds of years previously, gradually declined.
Green roof revival
Little change occurred all the way up to the 1960s when, in Germany, the modern method of creating living roofs, with growing media, root barriers, drainage layers &c., was invented.
Since this time, the popularity of green roofs has been increasing again thanks to the environmental benefits and advantages they can have over standard roofing materials. Over 10% of roofs in Germany have now been ‘greened’, with over 30 million square metres of living roofs constructed in the country since the year 2000 alone.
21st century legislation
Most recently, governments have been recognising the benefits of green roofs, and some have even taken the step of legislating them into building regulations.
The city of Toronto, Canada requires that buildings with a roof area greater than 2000 square metres have a set percentage of living roof. The main reason for this is to prevent drainage systems in the city being swamped by storm water runoff and to help deal with pollution.
Tokyo, Japan has implemented similar regulations as green roofs can help to deal with the urban heat island effect whereby urban areas stay warmer than surrounding countryside due to the way the city alters the landscape, with ecological implications.
The leader in this arena is Switzerland, who has taken the step of legislating green roofs nationwide.
Green roofs on modern-day constructions
Insect-friendly sedum roof on new build property in Norfolk
Sedum green roof on the roof of Anglia Ruskin University in Cambridge
Though in no way required by law, many new construction projects in the UK are choosing to install living roofs. Already, one of the largest living roofs in the world is to be found on the 35000 square metres topping Rolls Royce’s Goodwood factory and as more people become aware of the benefits of a living roof, their popularity is set to increase into the future.