Deck Post & Bearer Spacing: What Canberra Conditions Require

Search online for deck post spacing and you'll find a single number repeated everywhere, presented as if it applies to every deck. It doesn't. Post and bearer spacing is one of the parts of a deck you genuinely can't get from a generic chart — it depends on your soil, your timber, your deck's height and how you actually plan to use the space. Here's what really determines the numbers on a Canberra deck, and why we engineer each frame rather than copy a spacing figure from a website.

Why Post Spacing Isn't One-Size-Fits-All

A generic "maximum post spacing" figure assumes a specific bearer size, a specific timber grade, and a specific load — change any one of those and the safe spacing changes with it. Two decks that look identical from the backyard can have completely different framing requirements underneath, depending on what's actually holding them up. That's why we treat published spacing figures as a starting reference point for a conversation, not a number we plug straight into a build.

Factors That Change the Numbers (Soil, Load, Height, Timber Species)

Soil bearing capacity varies across Canberra, and our clay-heavy ground doesn't behave the same everywhere — what a footing can safely carry on one block isn't guaranteed on the next. Deck height matters too, since taller decks carry more wind and bracing load through the same posts. Intended use changes the load calculation directly: a quiet reading nook takes a very different live load to an entertaining deck built for a crowd around the BBQ. And timber species and grade set the ceiling on how far a bearer can span before it needs another post underneath it — a hardwood bearer and a treated pine bearer of the same dimensions won't carry the same span.

Typical Spans for Common Canberra Deck Sizes

As a general starting point, and considering our local soil types and typical deck designs, we usually work to a maximum post spacing around 2.4 metres on standard Tuggeranong builds. That figure moves depending on your deck's height, how you intend to use it, and whether you're planning features like built-in seating or a pergola overhead — both add load that the frame needs to be sized for from the start, not added on afterwards.

Why We Engineer Rather Than Guess

Rather than applying a blanket spacing figure, we assess each site individually — soil conditions, deck height, intended use and material choice — and size the posts, bearers and joists to suit. That includes matching bearer spans to the actual timber species being used, whether that's a hardwood frame or treated pine, since the two aren't interchangeable at the same spacing. Our custom deck design and build process starts with this assessment before a single post goes in the ground.

What Under-Spec'd Framing Looks Like Down the Track

Framing that's spaced too widely for its load doesn't usually fail outright — it shows up gradually instead. Noticeable bounce or springiness underfoot is often the first sign, followed by boards that cup or move slightly at their midpoint between joists. Screws can work loose over time as the frame flexes more than it should, and in more advanced cases you'll see visible sagging between posts when you sight along the bearer line. None of these are things you want to discover a few years into owning a deck, which is exactly why getting the spacing right at the framing stage matters more than almost any other structural decision on the build.

Get Your Frame Sized for Your Actual Block

If you're planning a new deck in Tuggeranong and want post and bearer spacing calculated for your soil, your design and how you'll actually use the space — not a generic online figure — our local team can walk the site with you before any framing decisions are locked in.