Structural Timbers
Bearers, joists, posts and ledger beams are the major structural components of any outdoor deck and are responsible for the support framework underneath the floorboards. Timber and LVL is used most commonly in domestic installations although steel may be substituted. The rating and profile of structural components relies most importantly on spans and loadings. Material used on the deck, location and landscape, design and deck related bushfire risk are also key considerations. Treated softwood (H3, H4 and H5) structural timber is used in most decking situations with Hardwood and Engineered beams also consistently used. Span tables are available here. For alternative sizes, spans and stress grades or for members supporting roof loads, refer to AS 1684 Residential timber-framed construction.

Timber Selection
Posts in contact with the ground should be either preservative treated pine or In-ground Durability Class 1 hardwood, with any sapwood preservative treated. Decking and deck framing above ground should be either preservative treated pine or Above Ground Durability Class 1 hardwood. Hardwood decking boards and deck framing containing sapwood must be preservative treated. Preservative treatment for posts in the ground and framing on the ground, shall be to hazard level H5. Preservative treatment for framing more than 150 mm above ground shall be H3.

Termite Protection
Physical and/or Chemical barriers must be provided to protect the deck and to ensure termites do not bypass protection systems to adjacent structures. Termite barriers must be designed so that they can be readily inspected and maintained. Where adequate termite protection is not provided to decks, they should be completely isolated from any adjacent structure. Click here to find products to help you.

Fixings
Post stirrups shall be hot dipped galvanised. Bolts, screws and nails shall be have a protective coating or stainless steel (not zinc plated). Joist hangers, framing anchors, plates, etc should be either hot dipped galvanised, stainless steel or with a fused or baked epoxy coating installed in accordance with manufacturer’s recommendations.

Attaching Decks to House
Ledger beams should be installed in treated pine or hardwood, fixed to house framing (studs, joists or bearers) with 12 mm dia. hot dipped galvanised bolts or coach screws at 900mm maximum spacing. Ledgers may also be required to be fixed with masonry anchors to structural brick or block walls. This should be carried out in accordance with manufacturer’s instructions.
Note: Brick veneer or other single skin brick walls may not be structurally adequate and require additional piers or freestanding posts.

Bracing
Decks should be braced to prevent lateral movement. The type of bracing would depend on whether the deck is freestanding or attached to a structure and its height off the ground. Further guidance should be sought. Placement and fixing attachment will depend on whether the deck is freestanding or attached to a structure and its height off the ground. Click link for more detail on bracing of Residential Timber Decks by Timber Queensland Limited

Resealing
All timber cut ends should be treated with a preservative to keep the treatment envelope intact.

The following information may assist in planning, specifying and ordering structural components

Span tables, Timber Class and Treatment
TABMA Softwood Span Table Domestic <PDF>
Australian hardwood domestic deck span tables <PDF>
Tilling Smart LVL 15 Design Guide <PDF>
Timber preservative treatment & Class guide <PDF>
DesignPine Specification details <PDF>
Design Pine Engineering detail <PDF>

Softwood Information
Design Pine Structural Profiles for NSW & QLD <PDF>
Designpine Brochure NSW <PDF>
Designpine Brochure QLD <PDF>
Design Pine Installation Guidelines <PDF>
Designpine MSDS <PDF>

Renovator Project Sheet
TABMA Project Sheet - Deck <PDF>

Safety
QLD Deck balcony window safety Guideline<PDF>

Disclaimer:While Hudson Building Supplies offers this information as a guide only. All views and information provided are not necessarily those of the management or staff of Hudson Building Supplies. All product information should be verified with the supplier or maker of the product. Any Work, Health Safety information is of a general nature and should not be taken as actual advice or adherence to legislation. Hudson Building Supplies accepts no responsibility for the content of third party websites.  Hudson Building Supplies accepts no liability for errors or omissions of any kind, whether they be negligent or otherwise, or for any loss, damage or other consequence which may arise from any person relying on information stated in any of the information provided.