What is the maximum possible pitch for a green roof?

Green roofs, or living roofs – which can be defined as roofs that are partially or fully covered with plants and vegetation – are a popular choice for many settings, and have various potential benefits.

Those benefits include, in addition to enhancing the aesthetic appeal of the building to which the green roof is fitted, the ability of such roofs to attract wildlife and insects and to restrict surface water run-off.

However, with regard to your own potential projects, you may be interested in knowing whether there is any limit to the pitch that can be specified for a green roof.

So, below, we will answer that question, while considering some of the factors that should guide your decision-making on the potential incorporation of sloped green roofing into your project.

So, is there such thing as a green roof maximum pitch?

In short most roof pitches can potentially accommodate a green roof, however the exact design may require the use of additional geosynthetic systems including geocellular retention webs for the substrate.

A very shallow pitch of five degrees or less may have little or no effect on the fundamental design of a green roof, compared to if the roof had been a flat one. However, if the green roof is steeper than this, there are certain practical factors that will need to be accounted for in the design.

Although most vegetation is able to grow on even relatively steep slopes, the process of installing a severely steeped green roof in the first place may be somewhat more complicated than the process for a shallower pitch.

Furthermore, careful thought needs to be given to how a pitched green roof will be maintained. If the slope is pitched at more than 25 degrees, it is likely to be too steep to walk on. This may necessitate the addition of certain design features to make maintenance easier.

The steeper the pitch of the given roof, the more likely the vegetation could slip down the roof due to an unstable substrate.

The key thing to remember, though, is that it is absolutely feasible to have a green roof created that does not suffer from such issues. You will simply need to ensure the design accounts for this, retaining water and keeping the substrate securely in place.

What solutions does Teragéos offer to make your steep-pitched green roof system possible?

If you are interested in realising a green roof design for your own next project that will be high-quality and long-lasting even in sections where the pitch will be steep, Teragéos have market-leading expertise in this application.

In some areas of the roofing at the former sites, for instance, the roof pitch was as steep as 45 degrees, which is normally too steep to easily lend itself to the installation of a green roof finish. The final project incorporated a number of anchor points, as well as reinforcement geogrid and geocellular technology, in order to keep the growing media in place.

Would you like to learn more about our knowhow in relation to the design of green roofing systems, and discuss how we could cooperate in helping you realise your next project? If so, we would be delighted to have that conversation with you when you reach out to us via phone or email.