What Is External Cladding?
External cladding is a material applied to the outside face of a building as a protective and/or decorative finish. It is distinct from the structural wall behind it — the cladding sits in front of the wall, either directly applied or on a system of rails and fixings that hold it away from the structure with a ventilated cavity behind.
On residential buildings in the UK, cladding is used primarily on new-build timber-frame construction (where the structure is not masonry and a separate weather-resistant layer is required), on extensions (where a different external aesthetic to the main house is desired or required), on loft dormer cheeks and dormer fronts, and as an upgrade to the appearance of an existing building where render or masonry has deteriorated.
Common Cladding Materials for Residential Use
Timber cladding — including traditional feather-edge boards, shiplap, and modern engineered timber products — has a long history in UK residential construction and provides a natural, warm aesthetic. Timber requires periodic maintenance (staining or oiling, depending on species and treatment) and must be detailed correctly with adequate ventilation behind it and proper treatment of end grains to perform well over time. Modified timber products such as Accoya or thermally modified wood have significantly enhanced durability and reduced maintenance requirements.
Fibre cement cladding — boards made from a composite of cement, cellulose fibres, and other materials — provides a durable, low-maintenance alternative to timber with a similar aesthetic. Products such as Hardie Plank are widely used on residential extensions and new build in London. They are resistant to moisture, rot, and insects, and can be pre-finished or painted on site.
Metal cladding — including zinc, copper, aluminium, and Cor-Ten steel — is used more commonly on contemporary architecture and commercial buildings but appears on residential extensions where a modern, long-life material is desired. Zinc and copper patinate to distinctive natural finishes over time and have very long service lives when correctly detailed.
Brick slip systems — thin brick veneers applied over insulation boards or directly to a substrate — allow the appearance of brickwork to be achieved without the structural depth of full masonry. They are used on timber-frame and lightweight construction where brick appearance is desired but full brick is not practical.
Fire Safety and Building Regulations
The fire performance of external cladding systems has been subject to intense scrutiny and regulatory reform following the Grenfell Tower fire in 2017. For residential buildings above 18 metres in height, combustible cladding materials are banned. For lower-rise residential buildings, requirements under Approved Document B of the Building Regulations set out standards for external wall fire performance. Cladding systems must be appropriate to the height and use of the building.
For standard low-rise domestic extensions (single to three-storey), combustible cladding materials such as timber are permitted but must be used in compliance with the relevant regulations. Always confirm compliance with building control when specifying external cladding for any part of a building.
Planning Considerations
The external appearance of a building, including its cladding, is a material consideration in planning. In conservation areas or on listed buildings, cladding that changes the appearance of the property may require planning permission or listed building consent. Even under permitted development, materials must be similar in appearance to the existing house for works that are permitted without planning permission. Check planning constraints before finalising external material specifications.
Cladding Specification at RCB
At RCB Design and Build, we specify external cladding as part of the wider design and technical specification for extension and refurbishment projects. We ensure compliance with building regulations fire performance requirements and check planning constraints before materials are finalised. Contact us to discuss the external specification for your project.