Compacted earth, flagstone or rock – This is less common (for example, occurring in Coober Pedy in central Australia) but is effective when properly designed and built for climate and site (refer to Thermal mass). Such systems have either low or no embodied energy and minimal transport impact.
Low-mass floors
Low-mass floor system options include:
Lightweight steel framing – This has higher embodied energy than timber but is highly recyclable. Steel framing has greater durability in termite-prone areas and often has lower transport costs than equivalent timber structures. It is subject to rust in corrosive environments; galvanising can eliminate this but adds to embodied energy. It is usually more expensive than timber once subsequent fixing costs are included. Steel framing must be appropriately insulated or it will act as a thermal bridge, increasing the risk of condensation.
Lightweight timber framing – This has low embodied energy and is a carbon sink. Sustainably sourced plantation timber should be used. When designed and built for deconstruction (for example, screwed, not glued), this flooring has a high potential for reuse at the end of its life. Timber is subject to termite attack and, while termite proofing reduces this risk, nonphysical barriers rely on chemical treatments that have other environmental implications. It is relatively low cost.
Cross-laminated timber (CLT) – This is built in a similar way to plywood: 15–25mm thick layers of timber are laid with alternate layers at 90° to each other, forming panels from 90mm to 300mm thick. These can be used for floors, walls and roof structure, but always require weather protection and waterproofing. They are more commonly used in medium-density and high-rise buildings. These thick softwood panels have a small but useful insulation value. They will still require additional insulation on external walls, roofs and floors in all climate zones.
