What is a Green Roof?
Extensive green roof on a flat carport
A Green Roof is a roof, flat or pitched, which is covered with living vegetation of some kind. This vegetation is laid over a waterproof covering to keep the water from entering the property.
What are the benefits of a Green Roof?
- A Green Roof will reduce heating costs by adding mass and thermal resistance to a roof. This means your house will stay hotter in cooler periods and cooler in hotter periods.
- With a green roof you can grow flowers and even vegetables providing a completely different outlook to boring concrete tiles or felt coverings.
- A Green Roof will help to insulate your building against sound. The soil on the roof is able to block out noise at low frequencies while the plants help stop noise at higher frequencies.
- Your Green Roof helps to filter many pollutants out of the air as well as removing quantities of Carbon Dioxide.
- The Soil in a Green Roof soaks up a lot of rain water which is used by the growing vegetation. This reduces the amount of storm water channeled into gutters and drains, taking the burden off our sewer system.
Are there different types of Green Roof?
There are two main types of Green Roof although a third is a mixture of the other two.
Intensive green roof in office roof garden
Intensive Green Roofs: These are roofs which require fairly intensive maintenance. The soil is deeper than an extensive roof and the vegetation is usually larger or more intense. Intensive Green Roofs can hold larger plants and small trees etc and are usually for larger buildings and, again usually, allow for access, walks etc. A good use for an Intensive Green Roof is a herb garden.
Green Roof Vegetation
Extensive Green Roofs: Extensive roofs require the minimum of maintenance and are laid on a much thinner layer of soil. The plants used are usually of the Sedum species which are very hardy with water storing leaves. The extensive way of laying a Green Roof is excellent for a DIY Green Roof and it is the Extensive kind of Green Roof which is found on most domestic properties.
How can I lay my own Green Roof?
DIY Green Roofs can be surprising easy to create. A rubber sheet is laid on the roof first. This sheet is called an EDPM sheet (Ethylene Propylene Diene M(class rubber) and is hugely weather resistant. Just as well as it spends half of it’s life under water!
Laying edpm rubber covering to green roof
Then edging strips are laid to stop any soil or vegetation washing into the gutter or onto the ground in bad weather.
A vegetation mat is then laid over the DPM and cut (by hand) into little nooks and crannies to give 100% coverage
Cutting vegetation mat for Green Roof
Vegitation mats showing the thickness and shape
The vegetation mat used here is a recycled (CFC free) mat profiled with integrated clay minerals and plant feeding elements which act as slow release fertilisers. The mat offers structural protection as well as filtering out pollutants. It also stores large volumes of water.
Spreading substrate soil for green roof
An extensive substrate soil is then poured over the vegetation mat. The substrate contains many organic elements needed in ecological cycles. A 40 litre sack of substrate mix will cover an area of 1 square metre at 40mm deep. This is the ideal depth for an extensive Green Roof.
Sowing Sedum shoots for Green Roof
The Sedum shoots are then sown into the substrate mix. Many green roofing companies supply Sedum in a mix of 5 to 10 different types of seed for extensive Green Roofing. The shoots are scattered evenly over the leveled substrate and the roof is watered. No further maintenance required!
There are many companies on the market that supply green roofing materials so that you can make your own, but if you would like the job to be done professionally simply contact them for a quote!
