Residential timber framed construction part 3 - cyclonic areas

Overview of the Standard

AS 1684 Part 3 provides the requirements for building practices and the selection, placement and fixing of structural elements used in timber framing for Class 1 (houses) and Class 10 (i.e. garages) for both new buildings and alterations for wind classifications C1, C2 and C3 cyclonic areas.

This Australian Standard also provides procedures and practices to assist in determining correct timber sizes for given applications and bracing and connections requirements to ensure adequate structural performance of the buildings noted.

The standard may also be applicable to other classes of buildings where the design and structural loading requirements are within the limitations of this standard.

What does it include?

AS 1684 Part 3 contains 9 sections and 10 Informative and Normative Appendices and also provides timber span tables through supplements that relate to various wind classifications and timber types and stress grades.

The 9 sections of AS1684.3 consist of: 

• Section 1 provides the scope as noted in the overview above and the general requirements of the Standard including other Standards referenced, the limitations on the use, durability requirements, the various forces on buildings, timber stress grades, size tolerances and other information that can relate to other parts of the Standard
• Section 2 provides terminology and definitions relevant to timber members and construction methods including loading requirements and the span and spacing of timber members
• Section 3 sets out the requirements for the preparation of sites in relation to site clearing and drainage, the requirement for sub-floor supports and how to determine pad footing sizes for stumps, posts and piers
• Section 4 sets out the requirements for the construction of timber-framed floors including jointing and construction methods for timber framed floors which can, where applicable, be applied to decks and verandas and similar construction
• Section 5 provides the general requirements for the installation of both strip and structural plywood and particleboard flooring and also has provisions for the selection and installation of timber decking
• Section 6 provides the building practice and details for conventionally framed timber walls to be used in conjunction with the Timber Span Tables. It deals with all aspects of timber wall framing including lintels, ring beams, window trimmers and non-loadbearing timber walls
• Section 7 sets out the requirements for the design, specification and building practice for conventionally framed roofs to be used in conjunction with the Timber Span Tables. It provides details of various types of conventionally pitched roofs, ceiling framing, roof supports and fixing. It also provides boxed eave details and roof components not provided in the Span Tables
• Section 8 sets out the bracing requirements for sub-floors walls and roofs. It provides information on temporary bracing during construction, provides methods to calculate the required amount of permanent bracing and details bracing units and components used in bracing buildings
• Section 9 specifies the fixing requirements between the various structural components and materials of a house. It details the various fixing and tie-down methods for typical load actions that a building may encounter from the sub-floor structure to the roof

This standard also includes Appendices contain mandatory information and the Informative Appendices provides non-mandatory information to support the standard. The 10 informative appendices consist of:

• Appendix A provides typical construction mass that buildings need to support
• Appendix B provides the durability requirements for timber components for both in-ground use and components subject to weather. It provides information on both chemically treated timber and naturally durable timber
• Appendix C provides information on using direct linear interpolation to obtain table values for spacing’s, spans, stud heights roof masses and similar parameters Interpolation is the process of estimating unknown values that fall between known values for example determining a roof span for a roof mass that falls between the given roof masses provided in the Span Tables
• Appendix D provides an example of how to determine the foundation bearing area for a stump, post or pier and how bracing should be evenly distributed in proportion to the racking forces that occur on a house
• Appendix E provides information on moisture content for both seasoned and unseasoned timber and typical shrinkage rates for unseasoned timber. The information also provides the recommended average moisture content at installation for timber flooring through various climatic zones
• Appendix F contains an alternative method from Section 8 to determine racking forces for bracing calculation for hip and gable roofs only
• Appendix G provides the properties of the most common timber species found in Australia in relation to such things as strength and joint group, hardness, toughness and density. It also covers termite resistance to heartwood
• Appendix H provides advice on proper handling and storage of timber prior to construction for both seasoned and unseasoned timber to allow for satisfactory performance of the timber in construction
• Appendix I specifies typical fixing details for collar ties in conventionally pitched roofs when there are multiple rows of underpurlins installed
• Appendix J provides generic guidance on building practices associated with the installation of Engineered Wood Products (EWPs). It is important to note that manufacturer’s specifications can override this general guidance

Is the Standard referenced in NCC or other legislation?

Yes, AS 1684 Part 3 is referenced in both Volume One and Volume Two of the National Construction Code (NCC).

Who is the Standard for?

This standard primary users are building designs, architects, builders, carpenters.

Related Australian Standards

• AS 1684 Part 1 Design Criteria 
• AS 1684 Part 2 Non-Cyclonic Areas 
• AS 1684 Part 4 Simplified - Non-cyclonic Areas 
• AS 1720.1 Timber structures design methods

Related HIA information sheets

• HIA resource on AS 1684.2-2010 Residential timber-framed construction, Part 2: Non-cyclonic areas
• HIA resource on AS 1684.4-2010 Residential timber-framed construction, P4: Simplified-Non-Cyclonic Areas
• HIA resource on AS 4440-2004 Installation of nail plated timber roof trusses
• HIA resource on AS 3660.1 termite management

Getting a copy of the Standard

An electronic copy of this Australian Standard can be purchased through the Digital Australian Standards webpage.

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