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AS 1684 USER GUIDE Nominal vs Specific Fixings GUIDE TO THE USE OF AS 1684 Back

AS 1684 USER GUIDE Nominal vs Specific Fixings GUIDE TO THE USE OF AS 1684 Background Discussion AS 1684 Parts 2 and 3 provide nominal and (where required) specific fixing details for various wind classifications. Some confusion has arisen, as to if specific fixings are required, what nominal fixings are required in addition to the specific fixings. The key to this issue is given in Clause 9.6.1, first paragraph, second sentence that states:- "Unless otherwise specified, the details provided are in addition to nominal nailing (see Clause9.5)” The intent of this requirement is to ensure that even if specific fixings are required to resist uplift forces (tie-down connections), that other forces and actions due to gravity, shear andconstructionloads arenot overlooked. For some other situations, the addition of the minimum nominal nailing requirements would be redundant because the specific tie-down fixings provide far greater capacity to handletheother forces andactions (other thanuplift). Example: Example: A strap over a rafter may be required for tie-down of roof uplift forces, but this alone does not provide shear resistance to lateral wind pressure that acts on the side of thewall. The nominal nailing requirements (usually 2 skew nails through the rafter into the top plate) can however resist this lateral load. There are no nominal connections specified for roof battens to rafters/trusses, but specific tie-down is required (nails, screws, etc). The last sentence of the first paragraph in Clause 9.5 states that:- "Unless otherwise specified herein, not less than two nails shall beprovidedat eachjoint." As a minimum, battens are nailed by one nail to rafters/trusses. This is still the minimum requirement even when a specific fixing is required and obviously the "catch all" minimum 'two nail' rule is excessive for roof battens. On the other hand, if we consider another specific batten tie-down that may be required such as a strap over the batten, the detail shown in Table 9.25 (f) and (g) does not indicatetheneedfor anadditional nail. It is obvious in this case that for construction purposes alone, at least one nail should fix the batten to the rafter/truss prior tothefixingof thestrap. able 9.17 (a) 2/75x3.05 dia nails are given an uplift capacity and therefore they may be used as specific connections for tie-down and at the same time provide thenominal nailing. 2. Table 9.17 (g) Nominal nailing would not be required if the joist hangers were the initial connections installed, however it would be usual practice to skew nail the joist in position prior to attaching the joist hangers in which case2/75x3.05dianails wouldberequired. 3. Table 9.19 (d) Nominal nailing of studs to plates is required. 4. Table 9.21 (c) Nominal nailing of rafter/truss to top plate is required. SomeOther Examples: 1. T Recommendation Let commonsense prevail! If the first fixing used to connect one member to another is a specific fixing, and it also caters for construction, and gravity loads, then the additional nominal nailingrequirements arenot required. (The Code clause and table references given below apply to Part 2 and Part 3 unless specifically noted) Latest editions of this and other User Guides are available from www.timber.org.au FOREST PRODUCTS OOD Research & Development Corporation & 1 National Timber Development Council 1of2 June 2002 MASTER BUILDERS A U S T R A L I A AS 1684 USER GUIDE 1 Technical Advice Further technical information and assistance is available from the following Timber Advisory Services. Important Notice The information and advice provided in the publication is intended as a guide only. As successful design and construction depends upon numerous factors outside the scope of this publication, the Forest and Wood Products Research and Development Corporation and other contributors accept no responsibility for specifications in, nor work done or omitted to be done in reliance on this information sheet. Whilst all care has been taken to ensure the accuracy of the information contained in this publication, the Forest and Wood Products Research and Development Corporation and other contributors disclaim, to the full extent permitted by law, all and any liability for any damage or loss, whether direct, indirect, special or consequential, arising directly or indirectly out of use of or reliance on this guide, whether as a result of the Forest and Wood Products Research and Development Corporation or other contributors negligence or otherwise. This publication is a joint venture between the National Timber Development Council and the Forest and Wood Products Research and Development Corporation (FWPRDC) in association with Housing Industry Association and Master Builders Australia. The FWPRDC is jointly funded by the Commonwealth Government and the Australian forest and wood products industry. FOREST PRODUCTS OOD Research & Development Corporation & Website: www.timber.org.au/as_1684.htm Suite 607-609 Yarra Tower P O Box 69 World Trade Centre, Melbourne, Vic 8005 www.fwprdc.org.au 2of2 NEW SOUTH WALES QUEENSLAND VICTORIA Timber Development Association NSW Ltd. 13-29 Nichols Street Surry Hills NSW 2010 Tel: (02) 9360 3088 Fax: (02) 9360 3464 Email: showroom@tdansw.asn.au Timber Research and Development Advisory Council Limited 500 Brunswick Street Fortitude Valley QLD 4006 Tel: (07) 3358 1400 Fax: (07) 3358 1411 Email: info@tradac.org.au Timber Promotional Council 320 Russell Street Melbourne VIC 3000 Tel: (03) 9662 3222 Fax: (03) 9662 3666 Email: tpcvic@tpcvic.org.au NATIONAL Plantation Timber Association of Australia 830 High Street Kew East VIC 3102 Tel: (1800) 007 463 WESTERN AUSTRALIA TASMANIA Timber Advisory Centre (WA) Homebase Expo 55 Salvado Road Subiaco WA 6008 Tel: (08) 9380 4411 Fax: (08) 9380 4477 Email: info@fifwa.asn.au Tasmanian Timber Promotion Board Suite 22/11 Morrison Street Hobart TAS 7000 Tel: (03) 6224 1033 Fax: (03) 6224 1030 Email: fiat@southcom.com.au SOUTH AUSTRALIA Timber Development Association of SA Inc. 113 Anzac Highway, Ashford SA 5035 Tel: (08) 8297 0044 Fax: (08) 8297 2772 Email: peter.llewellyn@bigpond.com uploads/Ingenierie_Lourd/ as1684-1-guide 1 .pdf