Green Roof FAQ
What are the costs of a green roof?
This depends entirely on what you want: how fast you want results, the construction of the building it has to go on, and much, much more.
You could build a green roof with the bare, bare minimum to save costs, however they might costs more in maintenance during establishment.
We don't want to put a number up, because it is 100% project specific.
What is known is that a green roof installation means added cost, compared to a standard roof. These costs could be interpreted as lost dollars, however, in the long term, a green roof is cheaper than a conventional roof.
As a green roof protects the underlying roofing from harsh weather influences, the under construction could last over 40 years, whereas a conventional roof needs replacement at least 2 times during this period. Put the cost of re-roofing next to the initial cost, and a green roof results to be cheaper than a conventional roof.
You could build a green roof with the bare, bare minimum to save costs, however they might costs more in maintenance during establishment.
We don't want to put a number up, because it is 100% project specific.
What is known is that a green roof installation means added cost, compared to a standard roof. These costs could be interpreted as lost dollars, however, in the long term, a green roof is cheaper than a conventional roof.
As a green roof protects the underlying roofing from harsh weather influences, the under construction could last over 40 years, whereas a conventional roof needs replacement at least 2 times during this period. Put the cost of re-roofing next to the initial cost, and a green roof results to be cheaper than a conventional roof.
Can you put a green roof on an existing building?
Yes. Many green roof projects involve existing buildings. The building must first be checked by a structural engineer to determine if the structure can hold the added weight of a green roof.
Waterproofing must be in excellent condition, typically no older than 5 years, though having a green roof installed directly after the roofer has installed the membrane would be preferred.
Waterproofing must be in excellent condition, typically no older than 5 years, though having a green roof installed directly after the roofer has installed the membrane would be preferred.
What is the difference between a modular system and a traditional built up system?
A modular system is basically plants grown on a carrier in the form of a tray. They are laid directly on the waterproofing membrane or on the root barrier. The modules not only act as a carrier, they also have a drainage function, and thus an additional drain sheet is not necessary.
Typically, green roof modules are of the more expensive kind of methods to put a green roof up. Comparing the cost of a tray system with for instance a green roof build of separate materials, and growing medium, planted with Sedum plugs, than the cost are not always more for a modular system.
Some argue modular systems are not good, and you can find terrible roofs that have modular systems. However, there are modular systems that are working great, and there is nothing wrong with them.
You can find more on this under Technology - Materials -
Typically, green roof modules are of the more expensive kind of methods to put a green roof up. Comparing the cost of a tray system with for instance a green roof build of separate materials, and growing medium, planted with Sedum plugs, than the cost are not always more for a modular system.
Some argue modular systems are not good, and you can find terrible roofs that have modular systems. However, there are modular systems that are working great, and there is nothing wrong with them.
You can find more on this under Technology - Materials -
Can I grow food on my roof?
Yes. You can grow hearty drought tolerant herbs like rosemary, thyme, and chives on a green roof very successfully.
Traditional crops such as tomatoes and peppers require a deeper growing media depth with lots of irrigation and maintenance. In the end it comes down to how far you want to go with your green roof.
Traditional crops such as tomatoes and peppers require a deeper growing media depth with lots of irrigation and maintenance. In the end it comes down to how far you want to go with your green roof.
Can I use potting soil or any soil from the ground on a green roof?
NO! This is recipe for disaster. Growing medium is used not because it sounds cool or is an accessory designed by manufacturers. Growing medium is specially mixed and selected lightweight materials composed mainly of mineral components with very little organic matter that has been sterilized. This allows for a balance between water retention and drainage which is key for a green roof's success. Low organic matter is necessary to ensure a stable growing media, that will not settle in the long run (when you apply 4 inches, you don't want this to become 2 inches in 4 years, as organic matter decomposes) .
What is the maintenance involved in a green roof?
That depends on the green roof. A typical extensive green roof composed of a 4 inch system with mixed Sedums needs water sparingly for the first year and weeding every few months. The following year it shouldn't need any water and will only need to be weeded 3 to 4 times a year. After the second year it should only need to be weeded twice a year.
One of the most important things to do is to remove any growth of tree seedlings; this should be number one on the list of things to do.
One of the most important things to do is to remove any growth of tree seedlings; this should be number one on the list of things to do.
Do I need to water my green roof?
During the first year, regardless of plants or system used, it is recommended that you water to aid establishment. In general for a green roof to be “green” in terms of being ecologically friendly it shouldn't need to be watered after the first year. Irrigation wastes water and energy. Both are what the green roof should be conserving.
Plant material that is used on a green roof should be adapted to harsh conditions, as the growing medium dries out, weeds normally will dry, as they dry out as well, while Sedums will survive this harsh situation.
Having mentioned the above you could consider watering on a regular basis. This will make your plants look more lush and vibrant, AND SO DO YOUR WEEDS!
Plant material that is used on a green roof should be adapted to harsh conditions, as the growing medium dries out, weeds normally will dry, as they dry out as well, while Sedums will survive this harsh situation.
Having mentioned the above you could consider watering on a regular basis. This will make your plants look more lush and vibrant, AND SO DO YOUR WEEDS!
How long will my roof last with a green roof?
A properly installed and maintained green roof should outlive a regular roof 3 or more times, 40 to 50 years are not uncommon in Europe. Considering this fact, this means that the cost of re-roofing 2 times, would even out the added costs for a green roof during initial installation. A green roof even has a value at the end of its live, as plant material could be harvested, and applied on a new roof (selling the plant material again)
How do I check for a leak if I already have a green roof?
To avoid a needle in a haystack search the best thing that you can do for yourself and your green roof is to have your waterproofing checked for leaks prior to installation and to have a leak detection system installed.
Other thing to consider is to think ahead, and consider what you can do, before you install a green roof, that will limit damage, in case something is going wrong.
You could consider a fully adhere roofing system, that is bonded with the underlying structure. In case of a leak, it will appear on the underside.
Other option would be to create compartments, sealing sections off. in case of a leak, the damage is contained to only a section of the roof.
Conventional a roofing membrane will be applied over the entire roof, with insulation underneath. In the event of a leak, you will only find out, when it is too late, and the entire roof could be saturated, resulting in a complete tear down of the roof and in some cases the entire roof structure.
Electro Field Vector Mapping (EFVM) is very accurate and able to find leaks that traditional flood testing wouldn't. EFVM testing can also be done any time after the green roof is installed and is often cheaper than the cost of a waterproofing manufacturer's warranty. Yes. There are many different ways to set up growing medium and drainage supports to keep the green roof from moving. In terms of costs however, the price will increase with the steepness of the slope.
Other thing to consider is to think ahead, and consider what you can do, before you install a green roof, that will limit damage, in case something is going wrong.
You could consider a fully adhere roofing system, that is bonded with the underlying structure. In case of a leak, it will appear on the underside.
Other option would be to create compartments, sealing sections off. in case of a leak, the damage is contained to only a section of the roof.
Conventional a roofing membrane will be applied over the entire roof, with insulation underneath. In the event of a leak, you will only find out, when it is too late, and the entire roof could be saturated, resulting in a complete tear down of the roof and in some cases the entire roof structure.
Electro Field Vector Mapping (EFVM) is very accurate and able to find leaks that traditional flood testing wouldn't. EFVM testing can also be done any time after the green roof is installed and is often cheaper than the cost of a waterproofing manufacturer's warranty. Yes. There are many different ways to set up growing medium and drainage supports to keep the green roof from moving. In terms of costs however, the price will increase with the steepness of the slope.