How to Build a Living Roof
There’s something about a green roof that makes a building feel more comfortable. It fits into nature better and it even reduces your carbon footprint while making it possible to reap all the benefits of a green roof. You can enjoy watching your roof thrive, while enjoying the benefits of a cooler home and fresher air.
It’s becoming more common to see green roofs in both the countryside and the city. As interest picks up, it’s not surprising that more and more people are opting for something a bit more exciting than the average shingled roof. Why not see if this is a good fit for you and your space? After all, there are plenty of benefits and virtually no downsides.
What Is a Green Roof?
A living roof or green roof is simply a roof that has plants growing on it. For many people this looks far more attractive than the traditional shingles and it’s a good way to integrate your building with nature.
This type of roof may be flat or pitched, but both work equally well for the growth of plants. However, there are also two types of green roofs that you should consider.
Extensive Living Roof
This sort of roof is designed to require minimal maintenance and to work best for homeowners who don’t have a lot of time to fuss with their roof. Extensive green roofs are lightweight as they don’t have a lot of medium growing or tall plants. They are ideal for roofs that are pitched and difficult to access.
With this type of roof, you can expect to see nearly solid, low level vegetation that is just a few centimetres tall and includes moss, sedum, or grass. There may be some small flowers in there, as well, to break up the green.
Intensive Green Roof
You’ve likely heard of rooftop gardens and this is what is also referred to as an intensive green roof. They work best on flat roofs, since you’ll need to access the actual plants. The more intensive green roof is ideal for commercial or apartment buildings.
You’ll need a lot more soil for this type of garden and it may even support shrubbery and small trees, along with plenty of other plants. These may grow freely atop the roof, or in bins and planters. The roof should be quite strong, as it needs to hold the additional weight of soil and the water used to irrigate them. More and more buildings are opting for this experience to help enhance the roof.
Keep in mind that as the name suggests, this is a more intensive style of green roof and will require maintenance and ongoing attention.
You can also choose to have a roof that is somewhere between intensive and extensive. This type of roof will handle taller plants, but not trees or shrubbery and can still be pitched. It will require a little more work than the extensive green roof, but not nearly as much as the intensive option.
The Benefits of a Green Roof
Aside from looking lovely, a living roof has plenty of benefits that you can reap. These include the following:
Longevity: Having plants growing on your roof can help your roof stay in great shape for a longer period of time. It extends the life and performance of your roof.
Reduced Energy Usage: The green layer on the roof reduces the amount of energy you need to spend in order to maintain the indoor temperature. The plants create a sort of natural insulation that keeps the heat from reaching the interior and prevents the escape of heat, as well.
Wildlife: A green roof is the perfect way to attract more birds and insects to your area, which is particularly important in more urban spaces.
Air Quality: The extra greenery can help improve air quality and produce more oxygen. Again, this is especially important in urban areas.
Depending on the type of plants, you may reap other benefits, as well, such as fruit and berries, which can grow well on intensive green roofs. These give you many more options, so you can try out some different types of plants.
The Best Plants for a Living Roof
What type of plants should you consider for your green roof? That depends on whether you’re looking at an extensive or intensive roof. Ideally, you want a mixture of textures to create interest, so look for some flatter plants for an extensive roof, then add in some variety.
Mats of certain plants do well on extensive green roofs, including sedum, moss, and sempervivum. You can add in ferns and daisies for a little visual variety.
Perennials and ornamental grasses are good additions if you have a semi-extensive green roof. You should look for plants that are drought resistant and can handle the direct sunlight. There’s rarely much shade on a roof, so you’ll need to ensure that you have plants to withstand the sun.
Building Your Green Roof
Before anything else, you need to be sure that your roof can handle the weight you’ll be adding to it. You may need to talk to a structural engineer to determine this. Once you’re sure you can plant, it’s time to move on to layering your roof.
Waterproofing: Since you’ll be watering plants on the roof, it’s essential that the water doesn’t move through the roof to your building. This can be disastrous and cost a lot of money. Your roof will already have a waterproof layer, but it needs to be inspected to ensure there are no cracks or flaws where standing water might move through.
Root Barrier: The next step is to install a root barrier. This is essentially a polyethylene membrane that is spread over the roof and tacked down with tape. The barrier prevents plants from digging their roots into the roof and breaking it apart. Unfortunately, plants can be quite invasive and may end up destroying your building if you’re not careful. The root barrier will prevent this.
Drainage Membrane: Next, you need a drainage layer. Water from rainstorms and such will tend to build up on the roof and can drown your plants, as well as cause issues for the rooftop if there are any tiny cracks or flaws. The membrane will ensure excess liquid drains away.
Filter: A filter layer membrane is another addition that can prevent debris from getting through to the drainage membrane. If soil fills up the drainage membrane, it will become blocked and no longer drain properly. This can be a definite hassle to fix because you’ll need to remove all the plants and substrate.
Growing Medium: The plants won’t grow on air and it’s not a good idea to put straight soil onto the roof. Instead, you should look for a growing medium designed for this type of growing situation. Ideally, the substrate should be fairly light and drain well, but sufficiently absorbent that the plants will receive enough water. The growing medium should be around 5 centimetres deep.
Plants: Once the layers of your green roof are complete, you can easily start to plant. If your roof is flat or slightly pitched, it should be relatively easy to plant everything. Sebum frequently comes in mats which can simply be laid out on the growth medium and watered. However, if you have a steeply pitched roof, you’ll need to make sure you can get the plants up there. It may require a ladder and a few tools to reach out and plant everything.
Finally, your roof is complete. At first, it may not look very impressive, since it’s all just getting started, but once the plants have taken root and the moss starts to spread, it can really look amazing. You’ll have your own piece of paradise, right on top of the roof.
Green roofs are great for businesses, homes, commercial buildings and everything in between. If enough people plant their roofs, it can actually lower the temperature in the summer within urban areas. The benefits are great and the fact that it is quite simple to build a green roof means there’s no reason you can’t do it.
If you need some help getting started with your green roof, James Dunn Roofing is here to help. Call us today for a roofing quote and we can take care of getting your roof set up for greenery.