STA ADVICE NOTE 18 AMENDED

As outlined in the original version of the STA Advice Note 18, the new guidance looks specifically at the specification and installation of external breather membranes for cavity facing structural wall panels. The recent updates highlight the need for all manufacturers to be able to verify all product claims, including for reflective membranes to be tested to BS EN 15976 and to claim aged thermal resistance figures which are fully independently certified by a third-party accredited body. Glidevale Protect is committed to providing full technical transparency to its customers and fully supports the renewed focus on providing specifiers with reliable technical information for external membranes which accurately reflects real life performance figures. In compliance with STA Advice Note 18, its product range of external breather membranes is tested and certified by a UKAS accredited, independent third party.

Glidevale Protect, one of the UK’s leading manufacturers of external wall breather membranes, welcomes the recent updates to the STA’s Advice Note 18 which highlight the importance of providing specifiers with trusted, and tested, technical product information.

First launched in 2019, Structural Timber Association (STA) Advice Note 18 –‘Breather membranes to structural walls’ is a valuable resource for contractors and specifiers involved in structural timber construction projects and the wider offsite construction market. The guide provides detailed information on the use of breather membranes in terms of watertightness, exposure, thermal performance and fixing requirements.

The new amendments to the document were published in April 2023 and have been compiled in collaboration with several specialist manufacturers including representatives from Glidevale Protect. The revised STA Advice Note 18 provides enhanced guidance on watertightness and specifically the use of W1 and W2 rated external breather membranes.

A new section on ‘site-specific exposure to wind-driven rain’ aims to clarify how to assess if a site is in a very severe area and if it would require a W1 rated breather membrane to provide the necessary resistance against water penetration. Guidance maps from BRE and NHBC are also included to highlight very severe areas of the UK where a W1 membrane is recommended. As one of the contributors to both the original and revised STA Advice Note 18, Glidevale Protect is well placed to assist specifiers and designers in choosing the most appropriate product for their project and offers a full range of both W1 and W2 rated reflective and non-reflective breather membranes for external walls.

In line with the recommendations outlined in the guidance, Glidevale Protect is also a passionate advocate of improving the way manufacturers communicate the technical performance of a product and specifically, clarifying if the quoted figures are based on aged or unaged values. As well as providing full transparency on the testing of its products, Glidevale Protect’s best practice ensures all its results take into account any brand printing on the low-emissivity surface and in addition, the aged thermal resistance values achieved are based on the membrane installed with the appropriate maximum horizontal fixing centres of 600mm, both which are detailed in STA Advice Note 18.

Specifiers can obtain a copy of the STA Advice Note 18 by contacting Glidevale Protect’s technical team directly at: info@glidevaleprotect.com or phone: +44 (0)161 905 5700

Further guidance on the specification of external breather membranes as part of the wall, floor or roof build-up within structural timber construction, including free U-value calculations, condensation risk analysis and take offs, is also available from Glidevale Protect’s technical team. For more information, please visit: www.glidevaleprotect.com or follow Glidevale Protect at: www.linkedin.com/company/glidevaleprotect/