Green roofing is in many ways exactly like any other do-it-yourself or home improvement project – you wouldn’t go out and buy major tools and materials for it without a list, and you wouldn’t (and shouldn’t) continue on to the building phase without a plan. As with construction, there are requirements for the structure and it is important to take your needs and the general climate into consideration as well.
To make an existing roof into a green roof, there are two options for approaching a retrofit job.One is to fit the existing roof onto your new green roof. The other is designing your green roof in order to fit the existing roof’s design. While the first option gives you the exact design and green roof that you want, choosing the second option can be both cheaper and take much less time to finish.
If you choose to go the more wallet-friendly and still creative route with a green roof, which is probably the way that most people will end up being set to doing, you can move on to the step about choosing a type of green roof. Otherwise, start with the structural assessment.
This step is really one that you will need a professional engineer of the architectural or structural division. Before you begin loading plants on top of your existing roof or planting a whole new shape of a roof on top, you have to know what to do to reinforce your roof to hold more weight than originally, or how much it can hold as-is.
Selecting a Type
Structural assessments really pave the way for the decision on a type of green roof. However, most buildings of a residential nature are very conducive to green roofing. This is because the green roofs used on residential buildings are generally quite light, though virtually every roof that is turned into a green one will have to be supported in some way to hold the little extra weight there will be. If you are designing your own extensive roof, you can design it to hold whatever load you end up going with.
There is also a type of green roof called an intensive roof, where there is a range of different plant types which require varying planting depths (eight inches to four or more feet). Existing roofs will require major renovations to get an intensive roof off the ground, so to speak, so this is something to seriously consider. The cost can go very high unless the roof was already being remodeled, so it’s important. Extensive roofing of your own design can of course be designed with this in mind, and most commercial and industrial roofs will take only a few changes of a minor nature to make them intensive roof-ready.
Select Plant Types
Though this step can sometimes be tricky, choosing the plants for your green roofing project is really as easy as knowing your climate zone. Try looking at the USDA’s Plant Hardiness Zone Map to find out which zone you’re in, and buying plants for your green roof accordingly. Intensive roofing is much broader in terms of types of plants to use because of the varying planting depths, while extensive plants are very popular for use with succulents like the Delosperma and Sedum families. Try asking for help from a landscape architect or the nursery from whom you will buy your plants.
This step is probably the most fun you’ll have while designing and planting your green roof – actually drawing up the landscape plan. Extensive green roofing makes this step easy. You’ll want to design and plant your succulents or other plant types in an order so that the roof never looks patchy in terms of blooming and hibernating plants, though all will be quite similar in their needs and care.
Intensive roofing makes this step a little more complicated because you’ll need to group your plants, of course according to planting depth, but also by their different functions, needs, and properties of aesthetics so that your green roof always looks very beautiful but still gives each individual plant exactly what it needs to thrive on the roof.