Deck Anatomy


deck anatomy

Note: These plans and/or instructions are to be used expressly as a guide only. If contemplating doing any building work inquire at your local building department to find out what specific needs are bound by local building code and what permits and/or consents may be required.

Note: All lumber should be suitable for exterior use and any lumber either touching the ground or going into the ground should be suitable for inground applications.

1) Stringers

Also called a ledger plate. The stringer is the piece of lumber bolted to the house upon which the joists are fixed on or to. The stringer needs to be packed out from the building at every bolt fixing to prevent moisture being trapped between the stringer and the building. The spacing between the bolts depends on the size of the stringer and the span of the joists which are fixed on or to it.
example: If a stringer is 100×50 (2×4) in size and if the joists fixed to that stringer span 2m (80″), the bolts that attach the stringer to the building should be 1.25m (50″) apart, where as if the joists span 6m (20ft), the bolts should be 0.5m (20″) apart.

2) Footings

A standard footing hole size for 100×100 (4×4) or 125×125 (5×5) post is 300mm x 300mm (12×12) square and 450mm (18″) deep in firm ground. In soft ground the holes will need to be bigger and deeper. Also holes will need to be deeper in ‘frost’ areas. 100mm (4″) of concrete is required as a pad beneath the post.

3) Posts

POSTS are Usually at least 100×100 (4×4). The spacing of posts along the bearer line depends on the structure of the deck.

4) Bearers

The size of the bearer depends on the length of the joists and the span of the bearer.

5) Joists 

The  joists are fixed to the stringer either by butting up to and fixing with joist hangers, or by sitting on top of the ledger plate and nailing through both faces of the joist.
The joists sit on top of the bearer and are fixed by way of nailing through each face of the joist into the bearer.
The size of the joists depend on the joist span and the joist spacing.

6) Decking

The thickness and strength of the various deck materials determines how far apart the joists must be.

7) Boundary joist

The boundary joist is fixed to the perimeter of the deck to give a neat finish. In most cases the boundary joist is decorative rather than structural, therefore another preference might be to replace the boundary joists with decking boards.

Building a Deck Construction Details – click here

Les Kenny started as a hobby for Les Kenny over eight years ago when he decided he would share his successful DIY projects with the wider world, putting them up online for anyone to access.

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