The Roof’s Not The Limit!

Wednesday, 04 March 2015

It’s not too often we encounter keen gardeners who think their garden is too big.  Once the gardening bug bites we’re always looking for more space in which to fit some home grown produce, new gadgets, a gorgeous new plant or focal point or simply to add colour and scent to our outdoor environment. However, there are always ways of squeezing more space out of your garden and this time we have looked to the skies for a solution. It’s the roof garden!

Roof garden

A roof garden can create more space to enjoy the outdoors

The roof garden is becoming more and more popular these days and not only can they be a great way to gain some extra space but they can convert a functional necessity into a stunning feature and can even help fight global warming. You need to take several factors into consideration first but there are simple methods you can use to create a little haven on your roof, balcony or even on a phone box.

Roof garden

This is one way to blend utilities into your garden!

Types of roof garden

There are two basic types of roof garden. A “green roof” is a roof or decking onto which plants are intentionally grown or wildlife is intentionally encouraged (so your old garage roof that’s sprouting moss or ferns doesn’t count!) This type is also called an “extensive roof garden.”  These are often in inaccessible areas and aren’t normally walked upon. An “intensive roof garden” can be anything you design them to be (just like a normal garden) and are meant for us to sit in and enjoy or use to grow produce.


Wildlife friendly green roof

We created a wildlife friendly green roof at Vialii Towers last year

Benefits of roof gardens

  • They absorb water and hence decrease flooding.
  • They can help to improve air quality in cities.
  • They can reduce urban air temperatures (air temperature in cities can be 5 degrees higher than rural areas.)
  • They can turn eyesores into beautiful areas in which to relax and reduce stress.
  • They provide excellent insulation against heat loss and noise pollution.
  • They can be a haven for wildlife.
  • They can be excellent viewpoints (not that we condone spying on your neighbours!)
Goats on roofs!

You can plant to encourage all sort of wildlife in your roof garden!

Sounds great so far, what specific things would we need to think about?

Factors to consider

  • Can the roof support the added weight? Bear in mind the weight of water too – wet soil can weigh a whopping 100lbs per cubic foot.
  • What access will you have? How easily can you transport tools, equipment, cups of tea and very importantly glasses of wine?
  • Do you need safety barriers for children?
  • How will you get water up there? Can you run a hose? Consider installing a water butt or a drip irrigation system.
  • Where will excess water drain?
  • Will you have any storage for tools, furnishings, children’s outdoor games?
  • How will you provide shade from sun or protection against wind for you/plants? Consider planting a windbreak of hardier plants with thick/hairy/waxy leaves which lose less water via evaporation.
  • If overlooked, how will you get any privacy?
  • Do your ideas requiring planning permission? Green roofs shouldn’t require planning permission but intensive roof gardens may.
Roof gardens in Rome

These roof gardens in Rome are havens of relaxation amidst the city bustle

Green roofs can sound a bit daunting but they needn’t be. If you plan your roof garden or green roof it will be easy to maintain.

Practicalities of growing

  • Containers or raised beds need to be deep enough to allow roots to grow.
  • Containers should be constructed of light and non-porous materials. Aluminium, zinc, light weight polymers are ideal.
  • Make sure containers are large enough. Anything smaller than 8 inches diameter (20cm) can’t hold enough soil relative to exposed surface area to preserve moisture levels.
  • Don’t let containers dry out. Mix in clay pellets to the compost to retain water. Add pebbles on top to reduce evaporation.
  • Don’t fill containers or raised beds to the top with soil as a slightly lower level will give your plants some wind protection.
  • Use lightweight soils such as perlite, vermiculite, coconut husk fibre or rock wool pad.
  • Try to acclimatise plants to similar conditions before planting on your roof.
Our green roof now that the plants are established

Our green roof now that the plants are established

Ideal plants

Of course your job is easier if you pick the right sort of plants to grow.  Hardy or indigenous plants with shallow roots are best suited to braving the weather.

Ideal choices for green roofs:

  • Sedums
  • Wildflowers, especially those used to living in limestone/chalk environments such as cows slip, rockrose, hawkweeds and thyme
  • Grasses
Pretty erigeron

Pretty erigeron works well in harsher environments

Ideal choices for roof gardens:

  • Erigeron (beach aster)
  • Gaura
  • Phormium
  • Cordylline
  • Coastal Plants
  • Lavender

Gaura can be a very pretty addition to a roof garden

Stunning examples of roof gardens

Hopefully we’re converting you to the merits of a green roof or roof garden.  For a bit more inspiration, why not visit one of these great examples:

New Lanark 
This imaginatively designed garden contains decorative planting with more than 70 different plants & shrubs that provide year round interest on the 9,000 sq ft roof.  There is also a central water feature and sculptures within Scotland’s largest rooftop garden.

New Lanark

Lulu getting some inspiration at New Lanark

Birmingham library
The new library opened in 2013 and has 2 roof garden terraces. The 3rd floor terrace has a produce growing area for local residents to get involved. The 7th floor terrace houses the Secret Garden, a quieter area with denser planting for more contemplative moments.

Birmingham library

One of the roof terraces at Birmingham library

Derry and Toms
London’s oldest roof garden originally opened above the Derry & Toms department store in 1938.  It’s 100ft above street level and contains ponds, bridges, walks, trees, shrubs and seating areas within its 1.5 acres. It’s now part of Richard Branson’s Virgin group.

Derry & Toms roof garden

Just one little bit of the fabulous Derry & Toms roof garden

So roof gardens and green roofs can be as extravagant or simple as you wish.  And any design will help reduce global warming as well as give you endless pleasure. If you’d like to explore the possibility of establishing a green roof or a roof garden please get in touch. We are happy to meet with you to discuss your requirements and options.

Best wishes,

All at Vialii

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