Cladding systems consist of 2 interacting components: the wall system (for example, lightweight timber framing) and the cladding layers. Cladding is a non-loadbearing skin or layer attached to the exterior of the walls. Its main role is to protect a building from water and the effects of weather; secondary roles can include sound, and thermal insulation and fire resistance. Your choice of cladding has a significant effect on your home’s environmental performance, cost, aesthetic appeal and property value.
Cladding can be made from timber, masonry, fibre cement, metal, PVC (polyvinyl chloride), or an increasing range of composite materials that combine 2 or more materials, often with a plastic binder. Many of these options are prefinished, requiring no additional coatings or painting. The performance characteristics of cladding materials vary substantially, and your choice of cladding should be based on a careful assessment of your climate and design needs.
By choosing cladding materials specific to an elevation or exposure, you can often achieve the best in physical performance and aesthetics. For example, in situations where a building’s external envelope does not need to be fully ‘sealed’ (for example, under deep verandas), highly breathable cladding can be an advantage. In areas or elevations with high exposure to sun, wind or rain, a very different approach is required.
Buildability, availability and cost
The buildability, availability and cost of cladding depends on the system chosen. Common cladding systems such as timber weatherboard or brick are readily available and well known in Australia. Less common or newer materials such as external insulation and finish systems (EIFS) will be less readily available, and you may need to find a builder who can work with your chosen material.
There are many types of cladding available, and thus a wide range of textures, colours, styles and finishes. The aesthetic outcome is limited only by the designer’s imagination, your budget, council regulations, or extreme site conditions.
Apart from aesthetic considerations, the colour of external cladding influences its capacity to absorb or reflect heat. In most Australian climates, it is preferable to use lighter colours or reflective finishes, especially for roofing. The use of darker cladding elements can be beneficial in colder climates.
Note: Local government regulations may require specific colours such as in rural or bushland areas. In warmer climates, the wall’s insulation may need to be increased to compensate for darker cladding.
Most cladding materials have a distinctive profile or texture that can create horizontal, vertical or angled patterns and shadow textures. Often a well-designed blend of cladding materials can offer both a pleasing appearance and match materials to specific conditions (for example, impact zones or areas requiring more frequent wash-down).
By definition, cladding is generally non-loadbearing (that is, it doesn’t carry roof or floor loads). However, some sheet cladding systems can have a structural bracing role in lightweight framing applications when appropriately fixed to the frame (for example, structural plywood, reconstituted timber, fibre reinforced cement sheeting). The fixing requirements for bracing cladding can have significant implications for visual appearance, waterproofing, condensation, ventilation, and drainage. The National Construction Code should be consulted for ‘acceptable construction practices’.
Durability and moisture resistance
The durability of a cladding system depends on the materials and finishes used. In some cases, the durability will depend on good maintenance (for example, timber weatherboards will need to be repainted or refinished to stay sound).
Cladding systems include horizontal or vertical boards, sheet materials, or smaller overlapping panels such as shingles and tiles. Each system uses different methods to prevent wind and rain entering through the joints, and each system’s effectiveness varies depending on wind direction and speed and the degree of exposure to rain. Install as per the manufacturers specifications.
Thermal mass and insulation
Regardless of its mass, cladding that is fixed to the outside of lightweight insulated frames makes no contribution to thermal performance in terms of thermal mass storage.
Cladding systems often contribute little to overall wall insulation values. However, several composite cladding products include insulation: those with higher R values eliminate the need for bulk insulation between the frame members in very mild climates. Condensation risk can be reduced with adequately designed, correctly specified and installed building membranes and draining cavities. Note that rigid foam insulation board is an impermeable vapour barrier, so it is essential to have drying and drainage cavities for these systems in condensation-prone climates.
With the exception of masonry veneer (for example, brick, earth, concrete, stone) – which is typically a high-mass, high-thickness system – cladding generally provides limited sound insulation. The contribution of denser products and foam insulation backed products is usually indicated as a weighted sound reduction index (Rw) rating or sound transmission class (STC). Individual suppliers will factor in these contributions to calculate typical whole-of-wall ratings.
Fire and pest resistance
Much of Australia is bushfire prone, and each site will need to be individually assessed to determine its bushfire attack level (BAL rating). Your local council can be contacted to provide guidance on zoning and whether your property falls within a bushfire-prone area, as well as what level of BAL is required. Material manufacturers and suppliers will have information on the specific BAL ratings that products comply with, following testing under specified conditions.
Pest resistance generally depends on construction design details rather than cladding properties. Composite cladding systems with soft expanded polystyrene (EPS) foam backing can harbour rats and birds if access for burrowing is not eliminated.
Non-timber systems and most reconstituted timber systems are not subject to termite attack, but inadequate detailing can allow termites to access a timber structure undetected. All timber cladding materials are subject to termite attack unless treated.
- Cladding is a material that is attached to the exterior of your home’s walls to form an outer weatherproof skin to the home.
- Cladding may be made of timber, masonry, fibre cement or metal. Newer products may combine several materials, such as insulated aluminium panels or poly-timber composite boards.
- Cladding systems need to be waterproof and should protect the interior of your home from the weather. They may also provide thermal and sound insulation, and be resistant to fire.
- Your choice of cladding system affects your home’s environmental performance, cost, aesthetic appeal, and property value.
- Identify the performance values you need to suit your climate and site, and consider these values before choosing any particular product.
- Also consider the environmental impact of your cladding system.