As Built Learning Exchange

Navigation

Location of sarking-type material

Published: 19 September 2011 / BCA 2011

The BCA defines sarking-type material as “a material such as a reflective insulation or other flexible membrane…normally used for…waterproofing, vapour proofing or thermal reflectance”.

Part 3.12 Energy efficiency

The Energy provisions have required increased levels of insulation. For roofs, the most cost effective way to achieve this has been to use bulk insulation at ceiling level. These provisions also required better sealing of doors and windows. This has made buildings less “leaky”, meaning energy is better contained inside and less energy is lost through air movement.

Whilst these both contribute to improved building energy efficiency, case-studies in the recently published ABCB Condensation Handbook suggest that higher levels of insulation and lower levels of air leakage increase the risk of interstitial (building fabric) condensation.

Part 3.7.4 Bushfire areas

The BCA requires compliance with the Acceptable Construction Manual AS 3959 (the Acceptable Construction Practice option, commonly called DTS, has been withdrawn).

These provisions apply for designated bushfire prone areas. In these areas, for BAL LOW up to BAL 40, metal and tile roof cover is required to have sarking under (BAL FZ (Fire Zone) roof construction must comply with AS 1530.8.2). The sarking required for BAL LOW to BAL 40 must:

  • Be located on top of the roof framing (tile roof battens may be fixed above the sarking and an insulation blanket (anticon) may be installed over metal roof battens), and
  • Cover the entire roof area including ridges and hips, and
  • Extend into gutters and valleys.
  • Note: Additional provisions apply for sealing of gaps, roof penetrations and the like.

Manufacturer directions

These typically reference AS/NZS 4200 and some state “to achieve stated R-values an air space of 40mm is required adjacent to each reflective foil face” and “we recommend that if installed under a metal deck roof…(sarking)...should be installed under the battens”.

Click the link below to download the full text version

Building Professional Registration or Login Required

To download the file insulation-moisture-barriers-sarking-location-lpn.pdf you need to login to the As-Built Learning Exchange. If you are a Building Professional and you do not have login access, you will need to register.