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Design and construction

Species selection

The specification of appropriate plant species is critical to the success of a green wall. Key considerations include:

Size – required coverage and also the load capacity of the building façade or supports.

Aspect – the aspect will determine the particular microclimate (direct sunlight, wind and rain). There are a wide variety of commercially available plants for all conditions, so with careful planning interesting plant combinations can be used around the building perimeter.

Climbing/ hanging mechanism – the particular requirements of species and their compatibility with the particular building façade material.

Appearance – foliage colour, quality and requirements for year-round cover (evergreens)

Biodiversity – the quality and quantity of roosting and nesting space, and the availability of food sources. The use of a variety of species can help to ensure that these requirements are met throughout the seasons.

Maintenance issues – species vary in the amount of maintenance they require. Plants need to be maintained to ensure the safety of the persons near the wall and the integrity of the building façade.

Structural considerations

Metal framework provides support for climbing plants, which woul otherwise not find anchorage on the smooth metal wall surfaces (courtesy P Early)
The choice of which type of green wall system to use will, to some extent, depend upon the construction of the wall onto, or into, which it will be placed. A façade should be assessed for its ability to accommodate extra load.

Supports need to be fixed securely to support the weight of the plants, plus wind and snow loads, and should be designed by a structural engineer. Freestanding structures or green wall anchoring systems that stand away from the wall surface may provide an appropriate solution where the façade is unable to take the loads.

Root space for climbers

Strong growth is required by plants used for façade greening, and so deep fertile soils are needed with a good supply of moisture. In many cases the foundations of buildings limit root penetration. Root tunnels can be introduced through impervious areas, and the use of soils with high organic matter and mulches can help to retain moisture and support a nutrient rich soil.

Maintenance
Vegetation on chimney pots (courtesy P Early)
To avoid damage to a building, it is important that the plants used are compatible with the building façade and that they are kept away from areas that should be clear of vegetation (e.g. drainpipes, vents).

Maintenance inspections will help to identify potential problems and enable these to be managed before any damage is caused to the building.

 




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