Q&A with Technical Manager David Kyburz

Posted 8 November 2019

Q&A with Technical Manager David Kyburz

Q: Is sarking required for a tiled roof in Canberra? 

A: There are several variables as to if sarking is required in Canberra.

To ensure that the performance of a tiled roof is not compromised by environment conditions the National Construction Code (NCC), Building Code of Australia calls up the Australian Standard AS 2050, Installation of roof tiles.

This standard requires that sarking is required when the wind classification exceeds the wind classifications of N3.

In brief summary wind classification relates to gust wind speed that affects the site of the house and the need for sarking to be installed.

There are several factors that need to be considered when determining the wind classification.

These factors include:

• the wind classification for the region - Canberra region is non-cyclonic and as such considered as Region A or normal as opposed to Region B which is considered Intermediate, Region C which is considered Tropical Cyclone and Region D which is considered Severe Tropical Cyclone.

• The Terrain category/ Shielding factor – is used to determine the exposure of the house/structure to wind as a result of its surrounds within a distance of 500 metres of the residence/structure. Basically, is the residence/structure exposed to wind or somewhat protected by trees and suburban housing, what obstructions around the house/structure that will influence the wind speed. 

• The Topography – is the classification to determine the effect of wind on a house/structure due to its location on a hill, ridge, relative to the height and slop of the hill or ridge. 

This information would be required to ensure that the roof installation standard is appropriate for the particular site. The provision of sarking should be noted on the approved plans.  

Your building certifier should be able to provide you with advice as to whether sarking would been appropriate/required. 

In addition to the requirement to provide sarking due to wind classification, AS 2050 also states that sarking may also be necessary in other circumstances depending on length of rafter, roof pitch and tile type.

 

Q: My client issued me with a list of items that he considers defective building work. The items include scratches in window glazing, a door not sealing and tiling work. What is considered acceptable building practice when it comes to the items that he has listed? 

A: I have had a similar question in relation to acceptable tolerances when it comes to finishes in building work that I recently answered in Q & A

There is a document called up under legislation that can be of assistance when considering what are considered acceptable tolerances to finishes in building work.  The document is called the Guide to Standards and Tolerances.

Basically the Building ACT 2004 requires building work to :

  • be carried out in accordance with approved plans;
  • the materials used in the building work must comply with the standards under the
  • building code for buildings of the kind being built or altered;
  • the way the materials are used in the building work must comply with their acceptable use under the building code for buildings of the kind being built or altered; and
  • the building work must be carried out in a ‘’proper and skilful way’’.

 

The Building ACT then refers to the Building (General) Regulations 2008 when considering whether building work has been carried out in a proper and skilful way.

These considerations include that work has been done to meet reasonable minimum industry standards.

The tolerances guide referred under the Building (General) Regulations 2008 to meet reasonable minimum industry standards is the Guide to Standards and Tolerances.  You may notice the Guide to Standards and Tolerances referred to in legislation is 2007 however the legislation also states the Guide to Standards and Tolerances as in force from time to time. The current Guide is the 2015 version.

The current Guide to Standards and Tolerances can be viewed or downloaded here. 

If you have any technical questions you may contact me on 6175 5954, mobile 0419 866 796 or via email dkyburz@mba.com.au

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