Having a garden on a flat roof isn’t something new – people have done this for thousands and thousands of years, wherever flat roofs were commonplace. While they’ve become much more sophisticated in modern times, and the science behind their benefits is something very contemporary, the appeal of this concept isn’t novel at all.
In fact, some cultures in various parts of the world went the whole nine yards with this idea, most famously being the grass and soil roof common to Scandinavia. The grass metabolizes a lot of the excess sunlight and heat, absorbs a lot of rainfall, discourages the formation of ice dams, and the soil is an excellent insulator, easy to replace and repair.
But we’re not talking about grass roofs – they have a lot of the same appeal and efficiency, but you can’t eat grass, no matter how much vegans will insist you can. Ideally, a garden should produce mostly edible things like fruits, vegetables and herbs, though some flowers and other decorative stuff doesn’t hurt, it’s just kind of pointless, especially up on a roof where nobody but you is likely to see it.
So, what exactly does a garden roof entail?
Basics of a Garden Roof
Depending on your roof, this can be taken to varying degrees. Some flat roof concepts have actually had soil placed across them, ad grass and landscaping and proper gardens put into place. If you’ve seen a lot of modern futurism depictions, you’ll see a lot of images showing buildings covered in a lot of green like this. The idea works, though if you don’t like nature, you will not find a city like this to be that appealing to live in.
More practically, roof gardens are like terrace gardens or a larger take on porch landscaping, with a lot of free-standing beds, pots and trays similar to that of a greenhouse, covering as much of the roof as possible. Going with this approach, anyone with some basic gardening knowledge and a reasonable (but not extreme) budget can readily set one of them up.
Depending on your climate, you may also need to provide irrigation and partial shade for some of the plants that need more water than rainfall can provide, and don’t like a solid 12 hours of sunlight.
Similarly, if you don’t live in a terribly sunny area, some plants may need the help of some grow lights from time to time. It’s best to pick the herbs, fruits and vegetables that naturally grow well in your climate, as when you begin devoting a lot of extra resources to this concept, you’re actually defeating part of the purpose, which we’ll get into next.
Fighting Water Damage
While the only way to fight water damage completely with a roof garden is to actually place soil across the surface, you can greatly reduce the amount of run off water and build up that comes from heavy rains, by placing a lot of vegetation on your roof to absorb it. Plants will store and lock up water, which can easily then be disposed of as a solid when you trim, replace and harvest your garden.
This puts a lot less strain on the street sewage, on your gutters, and reduces waste water all around in a very productive and useful way.
Sunlight is actually a menace to roofs, heating them to extreme temperatures, even on a cold day. While, again, the only way to completely block off solar heat is by spreading soil across your roof, a lot of plants covering as much as possible will soak up most of that sunlight, and put it to good use, keeping your roof much cooler, and thus making your electric bills lower as you have to fight the weather less aggressively.
This will also extend the lifespan of asphalt roofs, as sunlight causes warping, degradation and other such problems which hasten the decay and need for roof replacement in the long run.
Environmental benefits are more of a communal thing, but come on, let’s all do our part. Plants produce life-giving oxygen, and while their primary intake is CO2 (which itself is a pollutant problem in major cities), they’re also very good at scrubbing the air of other pollutants like carbon monoxide, fluorocarbons and much more, which means that if a lot of flat roofs have gardens like this, we could drop the pollution in suburban and urban areas by a significant percentage in years to come.
These gardens can also prevent the build up of other debris, snow, wind, hail and much more, especially if you have actual ground cover across the roof.
Roof types that are best suited for a roof garden are going to be flat roofs, though slightly-angled or very shallow slopes may be viable too. A traditional slanted or sloped roof is, for various obvious reasons, not a good idea unless you’re going for that Scandinavian soil/grass roof concept, and want to add some gardening to it.
We’ve alluded to there being two basic approaches to roof gardens, one more like an open-air hot house with racks and trays and pots, the other being to spread soil and do actual landscaping. The latter is a lot of work, and it can bring its own problems if the architecture of the building can’t support the weight of wet soil – which can become very heavy indeed.
However, in order to get the most out of protecting your roof from the elements and the sun, actual soil and “ground cover” across the surface is the most effective, if you have the resources and the budget to go all the way with the idea.
This type of landscaped roof garden has been done, most famously, penthouses built in the 1930s tended to use this, at the time modern marvel, to denote wealth, modernity and a sense of futurism.
Of course, this is only viable if you own the building, and local permits allow it, which isn’t always the case.
To learn more about various approaches to roof gardens and the many benefits they can bring, even the partial, more easily-done approach, fill out our contact form today.