Components of a Roof Garden

Living Roofs can seem daunting and complicated, but as long as the correct products are used, the systems are quite straight forward.

Bring your roof to life

A green roof offers numerous benefits including aesthetics, quality of life, environmental, storm water management and insulation.

What are the options?

There are three possibilities for roof gardens, each requiring its own assembly and plant make up.

  • Shallow assembly with grass and/ or sedum plants

Ideal for areas that receive little maintenance. Recommend plants include sedums and herbs; irrigation is not required if only simple plants and no grasses are utilised. Approx weight is 140Kg per square metre.

  • Medium assembly with plants

Plants for this assembly include sedums, herbs, and grasses. Un-irrigated systems can be created though, irrigation may be needed if grasses or diverse plant types are planted in semi-arid climates.
Approx weight is 240kg per square metre.

  • Deep assembly with trees and shrubbery

This system incorporates plants that require a greater growth medium depth and regular maintenance (watering, fertilising and mowing/weeding). A variety of plants can be used, including, turf grass, annual or perennial flowers, shrubs and even small trees.

Approx weight is more than 240kg per square metre.

Waterproofing Membrane

A waterproofing membrane is perhaps the most important part of a living roof system, stopping the water from rain and irrigation from entering the building. Having a robust membrane is vital as they are hard to uncover once the roof garden system has been installed.

When an anti-root membrane is used a root barrier does not have to be installed.

Growth media

Standard topsoil is not suitable as it will dry out and not sufficiently drain. A soil which is light and fast draining is required; a soil with two parts pumice perlite, one part topsoil and one part compost is suitable. The roof garden and type of plants will dictate the amount and depth of soil needed.

Plants

  • Drought resilient plants with shallow root systems are required when selecting plants for your green roof. Additionally, plants the flower and drop seeds are desirable to lower maintenance time.
  • Foliage Plants: asparagus, coleus, croton, dieffenbachia, dracaena, peperomia, philodendron, rubber plant, etc
  • Flowering plants: Seasonal flowers like Anthurium, Asters, Balsam, Calendula, Celosia, Cosmos, Daisy, Dianthus, Gaillardia, Marigold Nasturtium, Pansies, Phlox, Verbena, Zinnia, etc., and perennial flowers like Carnation, Chrysanthemum, Dahlia, Rose, Tuberose, etc.
  • Fruits:  Gooseberry, Strawberry, peach, pear, pineapple pomegranate, etc
  • Cacti and succulents: Agave, Aloe, Kalanchoe, Opuntia, Notocactus Nyctocereus, etc.
  • Vegetables: Eggplant, broccoli, chillies, lettuce, tomato, etc

Drainage board composite

This system is made up of two parts:

  • A layer of specially formulated fabric which absorbs and retains moisture for the soil to draw from.
  • The drainage board – A sheet of recycled plastic with upward-facing cups to retain the water.

This design provides a source of water for the garden to draw from and allows excess water to drain quickly.

Protection fabric – only needed for medium and deep assemblies.

A non-woven needle-punched fabric that resists soil chemicals, mildew and insects. It prevents damage to the membrane.

Root barrier

A polypropylene sheet that protects the membrane from root penetration.

Garden Edge

A 2mm thick extruded aluminium edge used to separate green roof assemblies and walkways or perimeters.

Drain box

Extruded aluminium drain box to keep areas clear of stone ballast or growth media.

A Drain Box and Garden Edge

Credits

Images supplied with permission from Viking Roofspec

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