Deck Specification

General

Building practice and procedures, workmanship, and the selection, placement and fixing of the various construction elements shall be in accordance with the following:

• Building Code of Australia

• AS1684.2 Residential timber-framed construction

• Guide to Standards & Tolerances (VBA)

• Construction drawings

Footings

Minimum Requirements:

Excavation holes 350x350x450 deep, 100mm into solid natural ground. Final depth determined by site conditions and Building Surveyor’s approval.

H4 treated pine/white cypress stumps fixed to 200x200x75 H4 treated pine sole plates to spread load to base of footing hole, and held in place with rapid set to facilitate accurate cutting of stumps to required level.

Footing holes backfilled to adjacent ground level.

Decks or balconies over 1.5m high may require engineer designed footings, including filled with 20MPa concrete.

Decking

UV stabilized PVC flashing (“Protectadeck”) to be tacked to top of joists, where exposed to weather.

Decking boards to be free from defects, including excessive warping and bending.

Gaps between boards to be consistent, and between 4.5 to 5.5mm wide for 90mm boards, and 6.0 to 7.0 for 140 wide boards.

Decking boards set-out using string lines to ensure straight lines, and fixed to each joist using machine-driven 65mm x 2.7mm stainless steel dome-head screw shank decking nails, or 10g 65mm square drive stainless steel screws. Nail fixings at butt joints and board ends to be hand nailed through pre-drilled holes to prevent splitting.

Framing

Framing members to be H3 treated lasercut KD pine, stress grade to suit required spans.

Sizing and spans designed according to the applicable span tables in AS1684.2

All fixings to be galvanized steel.

Concealed built-up bearers/beams  laminated together with 2.8mm 75mm framing nails through each side in a staggered diagonal pattern with maximum spacing of 2x the depth of beam.

Exposed built up beams laminated together with Type 14 batten screws one side only, spaced as above.

Bearers fixed to masonry walls with M10 galvanised dynabolts at centres to suit joist span (max 750mm).

Joists laid across bearers to be horizontal with maximum deviation from the horizontal of 4mm in any 2m, and 10mm overall.

Joists skew nailed from each side into bearers with 2/2.8 75mm framing nails.

Galvanised joist hangers used when required by project conditions, and only when concealed from view.

All cut ends and rebates of framing members to be sealed with timber preservative.

Important Note

The use of flashing and 65mm decking nails minimizes nails working loose and “popping” up above the deck with exposure to the weather over time. The flashing prevents water penetration into nail holes which would ultimately loosen nail grip, and also protects the joist. The 65mm long decking nails provide additional holding power compared with the 50mm long nails in common use. The stainless steel will not corrode in contact with the chemicals in treated pine, whereas galvanized nails (also in common use) will deteriorate in contact.

When comparing quotes for your project, please take into account the additional cost required to cover these measures that are included to ensure your projects serviceability and durability.