NCC 2019 & the Cladding Envelope
The 2019 NCC has now previewed to become effective in May, with a huge swath of changes being made across all sections. In terms of the external wall envelope, these changes have the potential to bring about significant change in wall design and processes into the future.
WHAT SPECIFICALLY IS CHANGING?
For volume 1 of the BCA, the three main areas of change for the external envelope are fire resistance, condensation management and energy efficiency.
WHAT IS THIS LIKELY TO MEAN FOR EXTERNAL ENVELOPE DESIGN?
- Deemed-to-Satisfy will be the most common route to compliance for fire performance of external walls, as the membrane concession allows both fire performance and condensation to be addressed as DtS. If a performance solution was to be used to assess fire performance, the combustibility of a sarking membrane would need to be factored into this. Additionally, the Fire Safety Verification Method has not been popularly received in the industry.
- The increased focus around thermal performance and condensation is likely to create more interest in externally installed insulation and rainscreen systems, as seen more typically in Europe. These serve to move the condensation dew point outside the structure, and provide a better insulated wall.
- In areas with higher wind loads or ventilated cavities, traditionally products such as galvanised sheeting have been used in lieu of sarking. The condensation requirements mean this system will no longer be compliant in many applications, and a breathable rigid air barrier or external sheathing board will be required.
If you have any questions around the 2019 NCC and how this will affect your cladding systems, or need assistance in designing a compliant wall build up, please get in touch with our technical team at [email protected]