8 Things to Consider When Installing a Green Roof

A green roof is a vegetative layer grown on a rooftop and is sometimes referred to as a vegetated roof, eco-roof, or living roof. When installed correctly, it provides numerous benefits. These include: improving the air quality, providing a habitat for wildlife and preventing gutters from overflowing.

By adding a green shed roof, you’ll be able to reclaim some of the outdoor space your shed has taken up, whilst enhancing the aesthetics of your garden. It’s a fantastic way to transform a dull, functional space into something that’s living, breathing and looks great too. It’s a win-win!

Here’s our guideline that outlines the important steps to install a successful green roof!

Getting Started

There are two types of green roof: intensive and extensive. An intensive green roof will require more maintenance, as it supports a variety of plants and utilises water irrigation systems.

Extensive roofs require much less maintenance, but the type of planting is limited to drought-tolerant and weather-hardy plants.

1. Preparation

Before you begin, you need to make sure that your existing shed roof is strong enough to take any extra weight. 

Typically, a basic lightweight green roof will weigh between 60 to 150 kg per square metre, and it will eventually increase when saturated with rain or snow.

Ensure there are no areas of damp, rotting wood, splits or holes. As for the roof, it must also be waterproofed. If you’re in doubt, an additional waterproof layer may be necessary.

2. Consider the Angle

When installing a green roof, it’s important to consider what angle it needs to be at. Although green roofs can be constructed on a flat roof, most shed roofs normally have a pitched roof— a roof that slopes downwards.

The pitch of the green roof should be around 9-10 degrees to help the plants thrive naturally in a rooftop environment and to reduce the need for retention as well to stop the roof from sliding or slipping.

Otherwise, if it’s on a slope over 20 degrees, a frame is necessary to prevent the roof from slipping.

3. Pond Liner

All green roofs should have an additional layer of waterproof material that is root-resistant. This will help avoid any water from seeping in, so make sure that the layer covers all the edges of the shed.

This can be a 300-micron damp proof liner, or you can opt for a single sheet such as pond liner.

4. Adding a Layer of Weed-Suppressing Membrane

Once you added the extra layer of lining, next is to put down a layer of weed-suppressing membrane — a material that can allow nutrients, water and air into the soil to maintain it’s good quality while preventing the weeds from growing.

In addition, a weed cloth can help to contain the roots, preventing them from growing down and through the bottom layers. Once you’ve secured this, you’ll need a layer that will help to retain moisture. Laying down some old blankets will do.

5. Rot Resistant Frame

When building a frame, it should be built out of rot-proof wood or lightweight materials to ensure the green roof elements remain contained. The frame can be made by simply nailing the corners together and should be the same depth as the substrate (soil) – normally 100mm minimum. 

That way, it can hold the soil and plants in place while preventing a waterlogged rooftop area. Moreover, consider adding holes to the side of the frames near the ground so that water can be drained from the roof.

6. Pea Gravel for Flat Roof

If your roof is flat or only has around a 5-degree angle, installing a thin layer of plea gravel over the plant protection fleece is an excellent way to drain the water without blockages.

7. Adding Soil


The key to low maintenance and the high-performing vegetated roof is adding soil. Using a lightweight soil or substrate can help reduce the weight being applied on the structure. 

8. Planting


When it comes to planting your new green roof, sedum plants, herbs, wildflowers and grasses work best as they are more resilient. Plus, they are attractive to a wide range of wildlife, including bees, butterflies, and birds.

If you have a pitched roof, remember that the plants at the top will receive less water than those at the bottom, so consider that when planting. 

A green roof surely does provide additional growing space, texture and colour to your garden. At the same time, providing more room for local wildlife. Even better, they help in a small but significant way of reducing carbon emissions while providing sound and heat insulation for your shed.

Are you looking for the perfect shed to achieve your dream green roof aesthetic? Available in a range of styles, sizes and materials, there is likely to be a BillyOh outdoor building to suit you. They can all be customised to suit your needs such as through colour and size. Therefore, ensuring you can get exactly what you imagine. Shop now!