How deep does a green roof need to be?

Generally speaking, ‘extensive’ green roofs are less than 6 inches deep, and, depending on depth, may support a range of plants. Think sedums (low-growing succulents), herbs, meadow grasses and perennials.

Can my roof support a green roof?

Can I have a green roof on my sloped roof? Yes. There are many different ways to set up growing media and drainage supports to keep the green roof from moving. In terms of cost however the price will increase with the steepness of the slope.

How much do green roofs weigh?

When fully saturated and with mature plant cover, a thin extensive green roof can weigh about 13 pounds per square foot. A more typical extensive roof with 3 to 4 inches of growing medium weighs 17 to 18 pounds per square foot, and a deeper intensive system can weigh 35 pounds or more per square foot.

Do you need planning permission for a green roof?

In most cases where green roofs are installed on existing buildings, planning permission is not required. However, it is always advisable when making any kind of alteration to a building to contact your local planning department.

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How much additional weight does a green roof add?

A traditional green roof can exert a load of up to 250 kg per m2 and that inevitably means a strong building is required to support the weight. In older buildings or new-build this may require costly structural reinforcement which in some cases may prove prohibitively expensive.

What are the disadvantages of green roofs?

Disadvantages of green roofs

  • A greater expense than traditional roofs. Unfortunately for green roofs, they do tend to be slightly more expensive than the traditional option. …
  • An increase in weight load. …
  • Require extra maintenance.

Is a green roof more expensive?

A green roof will be more expensive to install than a traditional flat roof, as the underlying structure may have to be strengthened to cope with the extra load. … Once installed, a green roof is beautiful, low maintenance, and eco-friendly.

Do green roofs really work?

Since your roof is covered by plants, the amount of it exposed to the elements is limited, enabling the roof membrane to last much longer than if unprotected. Green roofs reduce the amount of energy your house needs for heating, saving you money. The fire retardation provided by green roofs helps protect your home.

Can you put a green roof on an existing building?

Extensive green roofs are a popular option for homeowners as they are lightweight and require very little maintenance with no need for additional watering unless there is a prolonged drought. They are suitable for both existing and new build roof decks.

What is the point of a green roof?

Green roofs—sometimes referred to as ‘vegetated roofs’ or ‘eco-roofs’—consist of a waterproofing membrane, growing medium (soil) and vegetation (plants) overlying a traditional roof. Green roofs are used to achieve environmental benefits including reducing stormwater runoff, energy use, and the heat island effect.

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How much would a green roof cost?

Installing a green roof costs between $10 and $30 per square foot. Most homeowners pay within this range but costs could run up to $50 per square foot. While not common for residential roofs, some designs end up costing $200 or more per square foot.

How long will a green roof last?

Green roofs have a life expectancy of around 40 to 50 years, giving them a lifespan that outperforms a number of alternative roofing options considerably.

What factors are important when designing a green roof?

What are the most important factors in designing a green roof?

  • Climate, especially temperature and rainfall patterns.
  • Microclimates on the roof top.
  • Strength of the supporting structure.
  • Size, slope, height and directional orientation of the roofing structure.
  • Type of underlying waterproofing.

What can I plant on a green roof?

Top Ten Green Roof Plants

  • White stonecrop – Sedum album. When viewed en-mass, the flowers of Sedum album look like swathes of candyfloss. …
  • Widow’s cross – Sedum pulchellum. …
  • Meadow saxifrage – Saxifraga granulata. …
  • Two row stonecrop – Sedum spurium. …
  • Birdsfoot trefoil. …
  • Houseleeks. …
  • Sea thrift. …
  • Oregano.

What is the difference between intensive and extensive green roofs?

This is the easiest way to remember the difference – an extensive green roof probably has a shallow layer of substrate that covers a large area, whereas an intensive green roof often has a deeper layer of substrate, confined to smaller areas. … As the number and variety of green roofs has increased, so has the diversity.

How much water can a green roof hold?

It concludes that a green roof with 3-4 inches of soil can retain about one inch of rainfall. One inch of rain is equivalent to about 0.6 gallons of water per square foot of green roof area.

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Roofs and roofing