Pre-grown, low maintenance biodiverse green roofs

First off, before creating your own roof garden, you need to confirm with a structural engineer the weight loadings your roof can take.  Next you need to confirm how the roof garden will be used:  will it be for relaxing on in a deckchair for example or socialising with friends, or will it be a pretty sight that is overlooked but not actively used?

It’s important to confirm early on as it determines which system and build-up you should go for.  If you’re roof is to act as close as possible to a traditional garden, you need to start looking at semi-intensive or intensive green roof systems.  With these systems you are able to create a better garden feel, including shrubs, trees, a wide variety of other plants, pathways, seating and with the bigger build-up structure, the ability to walk and use the space recreationally. 

However, if you are looking to cover up an unsightly flat roof that is overlooked and are not planning on using the space recreationally, we’d recommend an extensive green roof system.  This is more budget-friendly and is often sold as a DIY solution (like our GrufeKit – green roof kit).  Plant choice is usually focused on the sedum varieties (which can turn lovely shades of yellow, pink, red, orange and different greens), wildflowers and other shallow-rooting plants. 

Essentially, your roof garden is dependant on the structure, how you will use the roof and your budget.  If you’d like to discuss which is the best fit for your roof, please get in touch with us!

A biodiverse green roof, often known as a brown roof, is generally intended to provide a habitat with diverse flora and fauna, unlike a traditional sedum roof (or an extensive green roof). 

Biodiverse roofs are often designed to either recreate or even improve a habitat lost through construction.

Whatever green roof system you go for, you have options to improve its impact on local biodiversity.  It’s good to bear in mind that soil plays an important role in supporting biodiversity, so the deeper the substrate (as long as it’s natural, and ideally an intensive substrate), the more benefits your roof is having for local ecology.

Let’s take a look at how you can design your green roof to support biodiversity:

Firstly, ensure you’re using a substrate (soil) that is natural and will support your chosen plant palette.  In the planting design, there is huge scope for improving biodiversity: focusing on native species (plants that are naturally found in your region); a variety of plants; using plants that provide sources of nectar, seed and fodder; using recycled aggregates, logs, rope and other materials to create piles which can become micro-habitats on your roof; and incorporating habitat homes such as beehives, bird and bat boxes.

Whether your green roof needs irrigation or not depends on the type of roof.  Irrigation is optional for brown and extensive green roofs, periodical for semi-intensive green roofs and regular for intensive green roofs.  It also depends on the location’s climate and immediate conditions (shady, full sun, windy etc) and the planting design.  Different plants require different levels of water, and for example, if your roof was in a windy location, the plants and soil would tend to dry out quicker, therefore requiring more water.

Most living roofs require maintenance, however the frequency and intensity can vary quite a bit.  Let’s take a look at the requirements for the four main green roof types:

Brown or Biodiverse roofs

Biodiverse roofs tend to require minimal maintenance.  As they are left to naturally seed (natural colonisation) and have the purpose of improving biodiversity, they reap the most benefits being left alone most of the time.  With any green roof type however, clearing gutters and debris is always recommended to maintain roof (and plant!) health.

Extensive green roof

Usually planted with hardy plants such as sedum varieties, extensive green roofs require low maintenance, simply clearing gutters of debris and clearing any leaves off the roof.  There are other optional maintenance tasks to carry out, such as hand weeding and removing any unwanted seedlings, feeding the roof with an organic phosphate and potassium feed, and keeping any stone perimeters clear of dead and live plants.  The GrufeKit is a good example of a simple extensive green roof system which requires limited maintenance.

Semi-intensive green roof

Semi-intensive green roofs require periodical maintenance, and we’d advice that you have a programme in place to ensure it is carried out.  As semi-intensive roofs tend to be designed with a greater variety of plant species, these will need tending to.  The frequency of the maintenance depends on the design of the roof, but at a minimum you’d need to schedule 3-4 visits per year.

Intensive green roof

Intensive green roofs require high maintenance, and as they are often designed for recreational use, or as a park-like garden, tend to involve a large variety of plants, including grasses, perennials, shrubs and trees.  Like a garden, they tend to require similar type and frequency of maintenance.