Why put a green roof on your garden shed?

Wet, wet, wet, that’s the only way to describe the tail end of 2013 and the beginning of 2014.  Some parts of Britain have seen awful floods and the forecast is for still more rain and maybe some snow later this month.

Still, at least it means we won’t be subjected to hosepipe bans this summer.

While it’s too wet to be working in the garden, sensible gardeners are making plans for spring.  Seed catalogues are being perused, measurements are being taken and prices are being gathered for features such as patios, wild flower meadows and fencing. 

If you are one of the planners, why not include a green roofing project for 2014?

A living green roof is both pretty and practical.  It has many benefits for you, your garden, the wildlife in your garden and indeed for the environment as a whole.  Here are just five reasons to put a green roof on your garden shed in 2014.

1.Provide food for bees, butterflies and other pollinating insects

small tortoishell butterfly on sedum2013 was a great year for pollinating insects.  The long hot summer saw an increase in the number of butterflies we saw in our gardens and although the late spring wasn’t great for honeybees, bumble bees and solitary bees, they soon caught up with themselves when the sun came out.


This year, many of our top garden designers are predicting that wildlife gardening and planting for pollinators will be high on the list of priorities for householders.  Great news for biodiversity!


Not every garden has room for a patch of wild flowers, a buddleia bush or a nectar laden fruit tree but nearly every garden has at least one shed/summerhouse/garden office/den.  A garden building with a carefully designed green roof can be just as valuable to pollinating insects as any herbaceous border.

Having flowers in bloom over a long period of time and in a relatively undisturbed location is just what butterflies, bees and hoverflies need to ensure the survival of their species.   If this nectar plot is fairly self-sustaining – which it needs to be if it’s on a roof – then the householder cum gardener will have very little work in maintaining the area and all the pleasure of having a beautiful and wildlife-friendly garden feature.

It’s a win-win situation for people and insects.

 2. Insulate your building so that you can use it more often

home insulationIf your summerhouse is anything like my summerhouse, You can’t use it during the winter months (too cold) or during the summer months (too hot).  I would imagine that similar levels of comfort also apply to a guinea pig hutch or a chicken coop in extreme temperatures, so this blogpost is relevant to animal housing as well as recreational spaces for people.

A living green roof is one of the oldest and most effective ways of insulating a building so that it stays warmer for longer in winter and cooler for longer in the summer.  The Vikings used green roofing on their dwellings and for good reason.  They had no central heating and relied on wood fire and good insulation for their comfort and survival.

In Nottingham Trent University, experiments compared the temperature beneath the membrane of standard roofs and living roofs throughout the year.  They concluded that a green roof averaged 1.3 degrees cooler than the air and a whopping 15 degrees cooler than a standard roof in the summer time.  In winter, the green roof was 4.5 degrees warmer than the standard roof and 4.7 degrees warmer that the air.

That’s pretty impressive, and when you consider that every 0.5 degree C can reduce electricity use for air conditioning by 8% - we’re talking some healthy savings on fuel bills too.

3. Make the neighbours jealous with a stunningly beautiful building

Image is everything.  We all of us garden for different reasons; as therapy, to grow food, to help local wildlife or because no one else in the house wants to do it. Nevertheless, whatever the reason, whatever our personal taste and whatever the main function of the garden, most of us want it to be admired.  A living green roof on a shed, garage or even a bin store, is guaranteed to  generate plenty of oooohs and ahhhhhs.

A green roof is also rather good at softening the lines of a garden building and help it to blend in to the landscape.

green roof on shepherds hutI recall the case of a lady from Fakenham in Norfolk who is lucky enough to have a beautiful garden overlooking meadows.  The lady, let's call her Sarah for I don't recall her name, is a keen and talented textile artist who, feeling the need to have a creative space separate from the home, built a light and airy summerhouse at the end of the garden where her sewing machine, fabric stash, threads and paraphernalia could live in peace.

But oh dear, her neighbours were not amused. They considered that the building spoilt their view. They were accustomed to looking out of their upstairs windows across green gardens, fields, meadows and hedgerows.  All of a sudden, BOOOM the view was interrupted by a white painted building with an asphalt roof. Not great. Until of course, Sarah had the sense to "hide" the building beneath a green roof. Now, viewed from above, the building is far easier on the eye and as far as I know, harmony has been restored.


 4. Preserve your waterproofing and help the shed last longer

While researching this article I read that In Noth West Europe alone, 500,000 tonnes of bitumous materials - mainly roofing felt - end up in landfill or incinerators every year. That's about 25,000 article loads. Scary!

The two main culprits for the failure of roofing felt are UV light and fluctuating temperatures. A green roof protects against both of these phenomena as well as that old favourite ... Mechanical damage from hobnail boots wandering about on a roof while the wearer inspects or maintains the roof or accesses roof lights, adjoining buildings, air conditioning units, Christmas lights etc.

Here's a graph showing how the temperature of waterproofing membrane changes throughout the dayon a green roof.  You can see how the green roof build up helps smooth out those peaks and troughs thus reducing the stress on the fabric of the waterproofing.

graph of temperature fluctation on a green roof

this graph is from Miami Science museum and shows how the roof membrane is protected from daily peaks and troughs in the temperature.

A green roof will double, maybe even treble the life of the waterproofing on a shed.  Not only will that save you from the cost of replacing the roofing felt......it will considerably reduce the amount of building materials that go into landfill.


5.Help prevent flooding

flooding in suffolk old postcode

Flooding is not a new phenomenon in this country as you can see from this
old postcard  but it certainly feels as though 'its happening more often

I live on top of a hill within half a mile of the Norfolk fens - which, thanks to an 18th century Dutchman and the modern day Environment Agency, are very well drained. I read news stories of flooded homes and businesses, animals lost, cars swept away by flash floods and I count my blessings for my home is unlikely to be affected in this way.

As a society we always seem to blame "them" for the country's inability to cope with rain, snow, drought or anything vaguely water-related.  I have no idea who "they" or "them" might be.....maybe government agencies, local authorities, planners, or the emergency services, I don't know. But maybe it's time to stop relying on nameless, faceless officials and for each of us to do a little something towards communal water management.

The practice of paving over front gardens to make car parking space (or easy care gardens) should take some of the blame for inefficient water management.  Rainwater can't soak in to concrete and so it makes it's way into the nearest drain. The drains become overwhelmed for they were built when gardens were soil based and there were far fewer building, roads, car parks and pavements in the country. When the drains are full and the ground is impermeable there is nowhere for the water to go, so it stays on the surface.  Simple.

But what if our roofs were absorbent? Surely this would offset some of the difficulties caused by impermeable ground. Well, green roofs are absorbent. A living green roof can soak up somewhere in the region of 80% of the rainwater that falls on it and once the roof is saturated, excess rainwater will drip or trickle onto the ground or into the gutter. Compare that to having gallons of water gushing off rooftops during a storm and it's not hard to imagine how much easier it is for drainage systems to cope with green roof runoff than with standard roof runoff.

green roof and natural lawn green roofs and grass lawns allow rainwater to drain away as nature intended

Another benefit of green roofing is that pollutants are filtered out of the runoff before they reach water courses.  All good stuff.

More green roofs = more benefits

Putting a green roof on just one shed won't prevent flooding in this country.  Just as recycling newspapers from just one household won't stop global warming and using washable nappies for one baby won't relieve landfill from a deluge of disposables.  But if almost everyone did it, what a difference it would make.


Click here to see some more photographs of green roof sheds


Find out how to create a green roof on your shed


Calculate the cost of installing a sedum green roof


Email Angela with any questions you may have