DIY Green Roofs | How To Make A Green Roof in 2021

We think green roofs should be a staple in every home. Especially urban ones.

Their ability to insulate homes, save on energy builds, manage runoff – alongside a host of other benefits – make them one of our favourite living mediums. And a fantastic way to use otherwise unwanted space.

But professional jobs are expensive. For the average home we estimate a living roof will cost around £7,000. But if you’re willing to take the job on yourself, you can save a (small) fortune.

What Type of Green Roof is Best for DIY Installation?

Extensive green roofs. Period. Especially if you’re a novice at building projects.

There are three main types of green roofs – intensive, semi-intensive and extensive. And of these three extensive roofs are the easiest to:

Install: Most extensive roofs only take a couple of days
Maintain: After the bedding in period, you’d only need to look at it a few times a year
Pay for: You would (probably) save in the thousands of pounds

They utilise hardier vegetation, can be installed by rolling out pre-planted mats and place the least load on the structure. As a green or DIY enthusiast, we strongly recommend you build an extensive green roof.

Check out our green roofs cost page for more pricing information.

Green Roof Structural Requirements - What you'll need

Material	Cost	Description
Waterproofing layer	£6 – 10 / m²	Typically a thin rubber used for it’s resilience and waterproofing properties
Root barrier	£3 – 6 / m²	An impermeable layer that prevents tree root and shrub damage
Waterproof drainage membrane	£7 – 11 / m²	Protects the waterproof membrane and allows for water attenuation and drainage
Filter Layer	£2 – 4 / m²	Typically a thermoplastic polymer that prevents substrate debris from entering the water storage or drainage component
Growing medium	£0.5 – 1 / kg	Soil or substrate can be used for a growing medium – the prices can vary and if you use sedum mats, you don’t need one
Vegetation and plant layer	£1 – 10 / plant	Hardy sedum plants are cheap and versatile, but you can spend significantly more on wildflowers and small shrubs
Frame	n/a	You’ll likely need to saw four lengths of timber to use as a frame for the roof – it aids in protection, but make sure it doesn’t block drainage

A step-by-step Guide to Green Roof Installation

Before you start...

Check your roof’s:

Structural integrity

Even extensive green roofs can weigh up to 150kg / m². So getting some professional advice as to the load your roof can bear is a sage move.

Angle

A flat roof has a much simpler design solution than it’s pitched counterpart.
With flat roofs you just build up the layers as per the manufacturer instructions.
With pitched roofs with a slope of 10°, you’ll need to find a solution for water retention and to make sure the soil stays in place.
As you can grow living walls, clearly angled roofs aren’t a huge issue. They can grow vertically. But for a DIY novice, this adds a layer of complexity to the project.

Decking

Check your roof’s decking quality, ability to manage load and waterproofing capacity

1. A Waterproofing Layer

A waterproofing layer (AKA a root proof membrane) is an essential first step in building your own green roof. When you initially inspect your roof deck you may find your roof already has a waterproofing layer – in which case skip this step – but if there isn’t you’ll need to install one to prevent leakage.

Something like a heavy duty pond liner is ideal. Particularly if you can fit one single layer across your roof. You can usually find these in your local garden centre.

2. Root Barrier

Root barriers sit just above the waterproofing layer and prevent roots from infiltrating and potentially damaging the structure. They’re usually just thin plastic membranes fixed to the waterproofing layer.

Root barriers are essential for intensive roofs due because larger plants and vegetation have a more invasive, extensive root structure.

Find our pick of the best root barriers here.

3. Water Storage and Waterproof Drainage Membrane

Arguably the most vital layer in your DIY living roof, a drainage membrane allows stormwater to drain into the guttering. Using a layer of pebbles will help avoid or alleviate blockages.

By alleviating water retention, it prevents structural damage to the roof and over-saturation to your plant life.

Whilst not all membranes cover drainage and storage simultaneously, we recommend purchasing one that does to extend your living roof’s lifecycle. Check out our favourite green roof drainage layers here.

4. Filter Layer

Then you’ll need to install a filter layer. So called for it’s ability to prevent soil, debris and substrate(s) from clogging up your drainage membrane.

Without a filter layer, your drainage membrane may not be able to function as it should, causing saturation and potential structural damage.

We’ve rounded up the best filter layers here.

5. Growing Medium

For plants and vegetation to grow they need a growing medium. Substrate – and we’ve rounded up the best lightweight, nutrient-light substrates on the market.

Most DIY green roofs have a substrate depth of 70 – 150mm+. It must be:

Lightweight
Low in nutrients: So it doesn’t encourage additional vegetation growth
Allow for sufficient drainage

If you’re using sedum mats, blankets or green roof trays, they don’t require an additional growing medium. For DIY extensive roofs this is perfect. They require:

No additional growing substrate
Minimal installation or bedding-in time
Minimal maintenance
Minimal watering – as they’re drought tolerant

If you decide to build a semi-intensive roof, you will almost certainly need to consider using substrate. One that is lightweight, drains well and absorbs enough water to support plant growth.

There are multiple varieties of green roof substrates on the market that support a variety of vegetation growth. They typically include aggregates, compost, clay soils and even volcanic rocks to provide the required traits for vegetation growth.

6. Vegetation Layer

This is the best part of building a living roof! You can inject your own personality and build a home for wildlife based on the seed mix you choose. Depending on the structural capacity, size and drainage capability of your roof, you’ll have a pretty good idea of what is and isn’t a good idea to plant.

The vegetation is primarily applied in two ways:

Pre-vegetated mats and trays: These can be ordered in rolled up mats and laid, much like turf and are often called green roof kits
Direct planting or seeds

For example, if you’re building a green roof on your shed – an intensive rooftop garden filled with trees and less-than-hardy shrubs is not a sensible move for a novice.

And What Plants Should I Choose?

Here’s a list of our favourite green roof plants for you to browse. But as an overview:

Sedum (or succulent) plants are always an excellent DIY green roof option and certainly what we would recommend.

Their ability to survive (relatively) extreme weather conditions, limited maintenance and lightweight, un-invasive root systems make them an amateur’s dream.

The fact they also come in pre-grown trays (or mats) and don’t need additional substrate makes them the simplest variety.

Wildflowers can survive in low nutrient substrates and provide aesthetic and biodiversity opportunities. They less hardy than sedum plants but work well on extensive DIY green roofs.

Tips for Planting

7. Frame

Once you’ve planted your vegetation and everything else is in order, you should build a frame around the perimeter of the roof.*

Made from rot proof materials, this frame should add much needed support and weather resistance to a newly built extensive roof.

Just make sure it doesn’t block runoff!

*You could build the frame before you start the job. This would be preferable if your roof is particularly open to the elements

DIY Green Roof Maintenance

DIY – particularly all sedum – green roofs are likely to require less maintenance than their larger, intensive counterparts. The sedum grasses and vegetation used on extensive green roofs are hardier than larger shrubs and vegetation found on intensive roofs. But you’ll need to:

Ensure plants are watered in dryer seasons
Ensure drainage outlets remain clear
Weed unwanted vegetation
Replant bare areas

Because of this you will probably only need to weed your DIY extensive green roof a few times a year. Honestly it should take less than an hour in total.

You’ll also need to water your roof – particularly to help it bed in. Whilst sedum grasses are generally drought resistant, if there are long dry periods you should consider watering.

However if you don’t want completely minimise your maintenance, you could purchase an irrigation system. They’re relatively cheap and simple to use.

DIY Green Roof FAQs

Do I Need Planning Permission for a Green Roof?

In most cases where you choose to install a DIY green roof you won’t need planning permission. However if you were to install a green roof without consulting your local planning department – only to find out you did need planning permission – you would likely need to uninstall it.

As a general rule we recommend asking your local planning department first.

How Long will a DIY Green Roof take to Install?

This is completely dependent on the:

Size of the project
Accessibility
Structural capacity
Type of green roof

You could build a green roof on a shed in a few days. Whereas a sloped house roof could take weeks.

How Long will a DIY Green Roof Last?

Green roofs can extend the lifetime of your roof by 300%. A conventional roof typically lasts for up to 25 years. A green variety could last for 55 years. A 200-300% increase in life expectancy is fairly usual.

Of course this completely depends on your property’s structural integrity, maintenance requirements, the plants and vegetation used. But rest assured it will significantly increase your roof’s lifespan.

Can I Build a DIY Green Roof on a Slope?

The short answer is yes. Roofs under 10° should have no problem with irrigation or drainage.

Pitched roofs at an angle over 10° will need professional help.

You can still do a DIY project on these roofs. But we’d be remiss to not suggest you get professional assistance at the beginning of the project.

Harry Clarkson-Bennett

An eco lover with a passion for sustainable design, Harry has years of experience in environmentally friendly content creation. With research and content featuring in The Times, Fox News, The BBC - alongside numerous other eco-outlets - Harry's passion for natural development brought about the Green Roof Guide.

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