There are five main categories of materials which can be used for the primary shading element.

standard building materials These include:

• metal or tile roofing

• timber

• concrete

• masonry

• other conventional building materials.

Significant advantages over other materials are their assured long life, non-combustibility (except for timber), waterproofing and resistance to vandalism. Given their long life, it is often possible to source these materials second hand, which reduces the need for the manufacture of new materials.

However, standard building materials are characterised by straight line geometry and, unless creatively and carefully designed, can lack aesthetic appeal. They also require a substantial supporting structure.

rigid translucent materials These include:

• treated glass

• polycarbonate

• acrylic

• fibreglass sheeting.

These materials block direct UVR while allowing the transmission of heat and diffuse light. They are most suitable for structures intended for winter UVR protection. Being waterproof, they also offer rain protection and can be used to collect water.

It should be noted, however, that many rigid translucent materials, especially the plastic-derived ones, carry a number of environmental costs. It is therefore recommended that rigid translucent materials only be used where some other environmental benefit can be achieved, for example, where their use may offset or reduce the need for artificial lighting or heating. Rigid translucent materials are typically supported at relatively close centres (approximately one metre) on metal or timber framing. Relatively high maintenance is required, both for cleaning and inspections of gaskets and fixings. If correctly installed, sealed and maintained, their life span is medium- to long-term.