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6 Simple Steps to Make a Green Roof

6 Simple Steps to Make a Green Roof

By Val Escobedo

There are two things to ask yourself before you start:

At what angle can I install a green roof?

• It is not recommended that you build a green roof on a slope greater than 10 ° without the help of an expert.
• It is recommended that a green roof be built on a slope of at least 2 °.

Can the existing structure support the weight of a green roof?

• Simple green roofs weigh between 60 and 150 kilograms per square meter.
• If you are not sure that your roof can support that weight, consult a specialist.
• When calculating the weight of the green roof you must also consider the weight when it is saturated with water or snow.
• If the existing roof cannot support the extra weight, you can reinforce it with wooden supports.

Step 1 - Layers of the green roof

The layers of a conventional green roof are shown in the following image:


Home green roofs require a simpler version of only 3 layers:

1. The waterproof membrane
2. The substrate
3. The vegetation

Step 2 - Waterproof membrane

Most roofs generally have a waterproof or waterproofing membrane. Green roofs require an additional layer of waterproof material that is also resistant to plant roots. Ideally this should go on a single sheet that covers the entire surface.

Sturdy 1-millimeter-thick pond covers, which you can find at garden stores, are ideal. They are fixed to the ceiling with conventional sealant. TIP: Mark the drains and exits so that you can open them before laying the next layers of your green roof.


Step 3 - Drainage

Excess water must be able to come off the roof. Drain outlets should open from the green roof container frame to allow water to drain into the roof gutters.

Drainage is very important; the ceiling must not be saturated so that the drainage outlets are free. Wear layers of pebbles to avoid blockages. The pebbles can also be used on the edges of the green roof to prevent vegetation from spreading.

Step 4 - Substrate

The depth of the substrate determines the vegetation that will grow in it. Most home green roofs are 7 to 8 inches deep.

The substrate needs to be light and low in nutrients. Avoid using common garden soil as they are very heavy when wet, they have a very high organic matter content that promotes growth and undesirable vegetation.

If you decide to make your own substrate, a good combination is to use 70.80% inorganic material, such as tezontle or ground brick, and 20-30% organic material, such as compost.

Step 5 - Sowing

The most exciting part of making a homemade green roof is the planting. You can design your green roof to attract certain types of plant and animal species or to reflect local biodiversity. Many landscaping suppliers already offer green roof seed mixes specially formulated to withstand weather and elevation conditions.

Vegetation can be applied in several ways:

1. Pre-seeded mats, these are delivered direct and installed similar to roll grass and generally consist of sedums or wildflowers.
2. Direct sowing of shoots, seeds or small plants.

The types of plants:

Sedum or succulent plants.- They are alpine plants used to living in elevated conditions. They require very little maintenance and survive all year round. Its flowers attract a wide variety of insects in the summer months.

Wildflowers.-They can survive in a low nutrient substrate and provide many options. The meadow flowers that are best adapted to green roofs are those associated with lime stone and limestone environments, such as helianthus, rose, bellflower, vellosilla and thyme.

To learn more about which plants to choose for your green roof, visit the following article: Choose What To Plant On Your Green Roof

Tips for sowing

• Avoid monocultures, as success on a green roof depends on establishing a community of self-sustaining plants.

• The steeper the roof is, the more important it is to ensure that the plants at the top are the most drought tolerant as they will receive the least water.

• To reduce the need for watering while plants are establishing, a green roof should be planted in the spring or fall.

Step 6 - Maintenance

The maintenance required for a home green roof is generally minimal. You should only check the following points once or twice a year to make sure your green roof survives.

o In the dry season make sure that the plants have enough water, especially in the first year, so that they spread correctly.
o After the first year, only water the plants if there is a drought of more than 6 weeks.
o Make sure the drainage outlets are free of garbage or plants.
o If there are areas on the green roof that did not grow, you can replant them with seeds or suckers from existing plants.

Green Roof Design Considerations

A frame of sturdy material should be built around the perimeter of the green roof. This will allow the green roof materials to stay contained. Make sure the frame doesn't block the roof drain. Be careful not to mistreat the waterproof layer when building this frame and opening the drain outlets. If there is a possibility of plants getting into the building and compromising the building structure, a 30 centimeter gravel margin should be placed.

If the slope is more than 20 ° you need to make sure that the green roof does not slip. To avoid this, you can put grid-type barriers on the waterproof membrane.

You can also divide your green roof into drawers or delimited areas so that you can walk between the spaces and live with nature.

To inspire you, meet 30 Incredible Green Roof Designs

Green roof environmental considerations

To maximize the environmental benefits of your green roof you need to take into account the following points:

• Avoid the use of chemicals and fertilizers on the green roof as they can contaminate the water that leaks there.
• Try to buy all the materials for your green roof from local suppliers to reduce the environmental impact of transportation.
• Consider using recycled materials from builders and merchants. Even for the substrate you can use gravel, just make sure it is clean.

A green blog


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