Deck span tables
Deck span calculator
Joists, bearers and posts
Pick your frame, put in the deck size, and see where the bearers and posts go. The plan redraws as you change it.
190 × 45 at 450 mm centres. Bearers can sit up to this far apart.
1,800 mm apart across the 3,600 mm depth.
5 per bearer, 1,200 mm apart. 2 / 140 × 45 spans up to 1,200 mm here.
On a 4,800 × 3,600 mm deck: 3 bearers 1,800 mm apart, each on posts no more than 1,200 mm apart. That’s 5 per bearer and 15 in all.
Plan view
4,800 × 3,600 mm · joists at 450 mm centresWant it drawn, counted and cut?The deck designer uses these same tables. It lays out every joist, bearer and post, adds breaker boards and the picture frame, and gives you a cut list. Free, no sign-up to start.
Open this deck in the designerJoist and bearer span tables
Treated pine · Steel · Aluminium
Maximum spans in millimetres for every frame, home and commercial. The row and column you picked above are lit up.
Treated pine MGP10 span tables
Treated pine MGP10 joist spans, home deck
Rows are joist sizes. Columns are joist centres.
| Joist · centres | 300 | 400 | 450 | 600 |
|---|---|---|---|---|
| 90 × 45 | 1,500 | 1,350 | 1,250 | 1,000 |
| 140 × 45 | 2,400 | 2,200 | 2,050 | 1,700 |
| 190 × 45 | 3,200 | 2,950 | 2,750 | 2,300 |
Treated pine MGP10 bearer spans, home deck
Rows are bearer sizes. Columns are load width, which is how far apart your bearers are.
| Bearer · load width | 1,200 | 1,800 | 2,400 | 3,000 | 3,600 |
|---|---|---|---|---|---|
| 2 / 140 × 45 | 1,800 | 1,550 | 1,400 | 1,250 | 1,150 |
| 2 / 190 × 45 | 2,400 | 2,100 | 1,900 | 1,700 | 1,550 |
Bearers are two pieces of 140 × 45 or 190 × 45 fixed together.
Treated pine MGP10 joist spans, commercial deck
Rows are joist sizes. Columns are joist centres.
| Joist · centres | 300 | 400 | 450 | 600 |
|---|---|---|---|---|
| 140 × 45 | 1,400 | 1,100 | 1,000 | 900 |
| 190 × 45 | 2,550 | 2,350 | 2,200 | 1,800 |
Treated pine MGP10 bearer spans, commercial deck
Rows are bearer sizes. Columns are load width, which is how far apart your bearers are.
| Bearer · load width | 1,200 | 1,800 | 2,400 | 3,000 | 3,600 |
|---|---|---|---|---|---|
| 2 / 140 × 45 | 1,400 | 1,200 | 1,100 | 1,000 | 900 |
| 2 / 190 × 45 | 1,900 | 1,650 | 1,500 | 1,350 | 1,200 |
Bearers are two pieces of 140 × 45 or 190 × 45 fixed together. Commercial rows use a 4 kPa floor load.
Spantec Boxspan steel span tables
Spantec Boxspan joist spans, home deck
Rows are joist sizes. Columns are joist centres.
| Joist · centres | 300 | 400 | 450 | 600 |
|---|---|---|---|---|
| B100-12 · 0.6 mm | 1,700 | 1,550 | 1,500 | 1,250 |
| B100-16 · 0.8 mm | 1,800 | 1,600 | 1,550 | 1,300 |
| B150-16 · 0.8 mm | 2,700 | 2,450 | 2,300 | 2,000 |
| B150-20 · 1.0 mm | 2,800 | 2,550 | 2,400 | 2,050 |
| B150-24 · 1.2 mm | 2,900 | 2,600 | 2,500 | 2,150 |
| B200-16 · 0.8 mm | 3,600 | 3,250 | 3,100 | 2,650 |
| B200-20 · 1.0 mm | 3,700 | 3,400 | 3,200 | 2,750 |
| B250-20 · 1.0 mm | 4,650 | 4,250 | 4,000 | 3,450 |
Spantec Boxspan bearer spans, home deck
Rows are bearer sizes. Columns are load width, which is how far apart your bearers are.
| Bearer · load width | 600 | 1,200 | 1,800 | 2,400 | 3,000 | 3,600 |
|---|---|---|---|---|---|---|
| B100-16 · 0.8 mm | 1,350 | 1,200 | 1,050 | 950 | 850 | 800 |
| B150-16 · 0.8 mm | 2,050 | 1,800 | 1,600 | 1,300 | 1,050 | 850 |
| B150-20 · 1.0 mm | 2,150 | 1,900 | 1,650 | 1,450 | 1,300 | 1,100 |
| B150-24 · 1.2 mm | 2,250 | 2,000 | 1,750 | 1,550 | 1,400 | 1,300 |
| B200-16 · 0.8 mm | 2,750 | 2,450 | 1,850 | 1,400 | 1,150 | 950 |
| B200-20 · 1.0 mm | 2,850 | 2,550 | 2,200 | 1,700 | 1,350 | 1,150 |
| B250-20 · 1.0 mm | 3,600 | 3,150 | 2,200 | 1,650 | 1,350 | 1,100 |
Each value is the shorter of Spantec’s 1.5 and 2 kPa figures, with its 1.25 × load-width rule for middle bearers.
Spantec Boxspan bearer spans on pedestals, home deck
Low Boxspan decks sitting on pedestals. These are shorter than on posts.
| Bearer · load width | 600 | 1,200 | 1,800 | 2,400 |
|---|---|---|---|---|
| B100-16 · 0.8 mm | 1,350 | 1,200 | 900 | 650 |
| B150-16 · 0.8 mm | 2,050 | 1,250 | 850 | 600 |
| B150-20 · 1.0 mm | 2,150 | 1,900 | 1,550 | 1,150 |
| B200-16 · 0.8 mm | 2,350 | 1,400 | 950 | 700 |
| B200-20 · 1.0 mm | 2,850 | 2,400 | 1,600 | 1,200 |
| B250-20 · 1.0 mm | 3,450 | 2,050 | 1,350 | 1,000 |
Spantec Boxspan joist spans, commercial deck
Rows are joist sizes. Columns are joist centres.
| Joist · centres | 300 | 400 | 450 | 600 |
|---|---|---|---|---|
| B100-12 · 0.6 mm | 1,350 | 1,200 | 1,200 | 1,000 |
| B100-16 · 0.8 mm | 1,400 | 1,250 | 1,200 | 1,000 |
| B150-16 · 0.8 mm | 2,150 | 1,950 | 1,800 | 1,600 |
| B150-20 · 1.0 mm | 2,200 | 2,000 | 1,900 | 1,600 |
| B150-24 · 1.2 mm | 2,300 | 2,050 | 2,000 | 1,700 |
| B200-16 · 0.8 mm | 2,850 | 2,600 | 2,450 | 2,100 |
| B200-20 · 1.0 mm | 2,950 | 2,700 | 2,550 | 2,200 |
| B250-20 · 1.0 mm | 3,700 | 3,400 | 3,200 | 2,750 |
Spantec Boxspan bearer spans, commercial deck
Rows are bearer sizes. Columns are load width, which is how far apart your bearers are.
| Bearer · load width | 600 | 1,200 | 1,800 | 2,400 | 3,000 | 3,600 |
|---|---|---|---|---|---|---|
| B150-16 · 0.8 mm | 1,600 | 1,400 | 1,250 | 1,100 | 900 | 750 |
| B150-20 · 1.0 mm | 1,700 | 1,500 | 1,300 | 1,150 | 1,000 | 850 |
| B150-24 · 1.2 mm | 1,800 | 1,600 | 1,400 | 1,200 | 1,100 | 1,000 |
| B200-16 · 0.8 mm | 2,200 | 1,900 | 1,450 | 1,200 | 950 | 800 |
| B200-20 · 1.0 mm | 2,250 | 2,000 | 1,750 | 1,500 | 1,200 | 1,000 |
| B250-20 · 1.0 mm | 2,850 | 2,550 | 1,900 | 1,500 | 1,200 | 1,000 |
Each value is the shorter of Spantec’s 1.5 and 2 kPa figures, with its 1.25 × load-width rule for middle bearers. Commercial rows use a 4 kPa floor load.
Spantec Boxspan bearer spans on pedestals, commercial deck
Low Boxspan decks sitting on pedestals. These are shorter than on posts.
| Bearer · load width | 600 | 1,200 | 1,800 |
|---|---|---|---|
| B150-16 · 0.8 mm | 900 | 550 | 350 |
| B150-20 · 1.0 mm | 900 | 550 | 350 |
| B150-24 · 1.2 mm | 900 | 550 | 350 |
| B200-16 · 0.8 mm | 900 | 550 | 350 |
| B200-20 · 1.0 mm | 900 | 550 | 350 |
| B250-20 · 1.0 mm | 900 | 550 | 350 |
InfraBuild DuraGal steel span tables
InfraBuild DuraGal joist spans, home deck
Rows are joist sizes. Columns are joist centres.
| Joist · centres | 300 | 400 | 450 | 600 |
|---|---|---|---|---|
| RHS 75 × 50 × 1.6 | 1,300 | 1,200 | 1,150 | 950 |
| RHS 75 × 50 × 2.0 | 1,400 | 1,250 | 1,200 | 1,000 |
| RHS 100 × 50 × 1.6 | 1,750 | 1,600 | 1,500 | 1,300 |
| RHS 100 × 50 × 2.0 | 1,850 | 1,700 | 1,600 | 1,350 |
| RHS 150 × 50 × 2.0 | 2,800 | 2,550 | 2,400 | 2,050 |
InfraBuild DuraGal bearer spans, home deck
Rows are bearer sizes. Columns are load width, which is how far apart your bearers are.
| Bearer · load width | 600 | 1,200 | 1,800 | 2,400 | 3,000 | 3,600 |
|---|---|---|---|---|---|---|
| RHS 150 × 50 × 2.0 | 2,150 | 1,900 | 1,650 | 1,450 | 1,300 | 1,200 |
| RHS 150 × 50 × 3.0 | 2,400 | 2,150 | 1,850 | 1,650 | 1,500 | 1,400 |
Sizes InfraBuild publishes no figure for are left out.
InfraBuild DuraGal joist spans, commercial deck
Rows are joist sizes. Columns are joist centres.
| Joist · centres | 300 | 400 | 450 | 600 |
|---|---|---|---|---|
| RHS 75 × 50 × 1.6 | 1,000 | 950 | 900 | 750 |
| RHS 75 × 50 × 2.0 | 1,100 | 1,000 | 950 | 800 |
| RHS 100 × 50 × 1.6 | 1,400 | 1,250 | 1,200 | 1,000 |
| RHS 100 × 50 × 2.0 | 1,450 | 1,350 | 1,250 | 1,050 |
| RHS 150 × 50 × 2.0 | 2,200 | 2,000 | 1,900 | 1,600 |
InfraBuild DuraGal bearer spans, commercial deck
Rows are bearer sizes. Columns are load width, which is how far apart your bearers are.
| Bearer · load width | 600 | 1,200 | 1,800 | 2,400 | 3,000 | 3,600 |
|---|---|---|---|---|---|---|
| RHS 150 × 50 × 2.0 | 1,700 | 1,500 | 1,300 | 1,150 | 1,000 | 950 |
| RHS 150 × 50 × 3.0 | 1,900 | 1,700 | 1,450 | 1,300 | 1,200 | 1,100 |
Sizes InfraBuild publishes no figure for are left out. Commercial rows use a 4 kPa floor load.
Clickdeck aluminium span tables
Clickdeck joist spans, home deck
Rows are joist sizes. Columns are joist centres.
| Joist · centres | 300 | 400 | 450 |
|---|---|---|---|
| Clickdeck 28 · 28 × 50 | 400 | 350 | 350 |
| Clickdeck 55 · 55 × 55 | 800 | 750 | 700 |
| Clickdeck 110 · 110 × 50 | 1,650 | 1,500 | 1,450 |
| Clickdeck 150 · 150 × 50 | 2,300 | 2,100 | 1,950 |
| Clickdeck 200 · 200 × 50 | 3,050 | 2,800 | 2,650 |
Clickdeck bearer spans, home deck
Rows are bearer sizes. Columns are load width, which is how far apart your bearers are.
| Bearer · load width | 600 | 1,200 | 1,800 | 2,400 | 3,000 | 3,600 |
|---|---|---|---|---|---|---|
| Clickdeck 28 · 28 × 50 | 300 | 250 | 200 | no figure | no figure | no figure |
| Clickdeck 55 · 55 × 55 | 600 | 550 | 450 | no figure | no figure | no figure |
| Clickdeck 110 · 110 × 50 | 1,300 | 1,150 | 1,000 | no figure | no figure | no figure |
| Clickdeck 150 · 150 × 50 | 1,750 | 1,550 | 1,350 | 1,200 | 1,050 | 1,000 |
| Clickdeck 200 · 200 × 50 | 2,350 | 2,100 | 1,850 | 1,600 | 1,450 | 1,350 |
Sizes and load widths Clickdeck publishes no figure for are left blank.
Clickdeck joist spans, commercial deck
Rows are joist sizes. Columns are joist centres.
| Joist · centres | 300 | 400 | 450 |
|---|---|---|---|
| Clickdeck 55 · 55 × 55 | 600 | 600 | 550 |
| Clickdeck 110 · 110 × 50 | 1,300 | 1,200 | 1,150 |
| Clickdeck 150 · 150 × 50 | 1,800 | 1,650 | 1,550 |
| Clickdeck 200 · 200 × 50 | 2,400 | 2,200 | 2,100 |
Clickdeck bearer spans, commercial deck
Rows are bearer sizes. Columns are load width, which is how far apart your bearers are.
| Bearer · load width | 600 | 1,200 | 1,800 | 2,400 | 3,000 | 3,600 |
|---|---|---|---|---|---|---|
| Clickdeck 55 · 55 × 55 | 450 | 400 | 350 | no figure | no figure | no figure |
| Clickdeck 110 · 110 × 50 | 1,000 | 900 | 800 | no figure | no figure | no figure |
| Clickdeck 150 · 150 × 50 | 1,400 | 1,200 | 1,050 | 950 | 800 | 800 |
| Clickdeck 200 · 200 × 50 | 1,850 | 1,650 | 1,450 | 1,250 | 1,150 | 1,050 |
Sizes and load widths Clickdeck publishes no figure for are left blank. Commercial rows use a 4 kPa floor load.
Futurewood CleverDeck aluminium span tables
Futurewood CleverDeck joist spans, home deck
Rows are joist sizes. Columns are joist centres.
| Joist · centres | 300 | 400 | 450 |
|---|---|---|---|
| 25 × 45 · ultra-low | 350 | 350 | 300 |
| 50 × 45 | 750 | 700 | 650 |
| 90 × 45 | 1,350 | 1,250 | 1,150 |
Futurewood CleverDeck bearer spans, home deck
Rows are bearer sizes. Columns are load width, which is how far apart your bearers are.
| Bearer · load width | 600 | 1,200 | 1,800 |
|---|---|---|---|
| 50 × 45 | 550 | 500 | 450 |
| 90 × 45 | 1,000 | 900 | 800 |
Sizes and load widths Futurewood publishes no figure for are left blank.
Futurewood CleverDeck joist spans, commercial deck
Rows are joist sizes. Columns are joist centres.
| Joist · centres | 300 | 400 | 450 |
|---|---|---|---|
| 50 × 45 | 600 | 550 | 500 |
| 90 × 45 | 1,050 | 1,000 | 900 |
Futurewood CleverDeck bearer spans, commercial deck
Rows are bearer sizes. Columns are load width, which is how far apart your bearers are.
| Bearer · load width | 600 | 1,200 | 1,800 |
|---|---|---|---|
| 50 × 45 | 400 | no figure | no figure |
| 90 × 45 | 800 | 700 | 600 |
Sizes and load widths Futurewood publishes no figure for are left blank. Commercial rows use a 4 kPa floor load.
How to read a span table
Four terms, numbered on the frame.
- Joist centres
- Gap between joists, centre to centre. Your board sets it. Tighter centres let a joist span further.
- Joist span
- Distance between the bearers a joist sits on. Look it up by joist size and centres.
- Load width
- The strip of deck one bearer holds up. For a middle bearer it’s half the gap on each side, which comes back to the gap between bearers.
- Bearer span
- Distance between the posts under a bearer. Look it up by bearer size and load width.
Joist spacing for composite decking
Maximum joist centres for home decks, from the install guides of 68 board ranges we list.
400 mm includes US boards set at 16 inches (406 mm).
450 mm is the most common, but not the rule. Nearly half want 400 mm or less. Check your board’s own guide before you set out joists.
Commercial decks need tighter joists. Most ranges drop to 300 or 350 mm centres for cafés, pool surrounds and anything public.
Angles cost you span. Boards laid on a 45° angle usually need closer joists. The board maker’s guide gives the figure.
Each board needs three joists. Many guides say a board must cross at least two spans. Don’t let a short board sit on only two joists.
Deck framing tools and guides
- Free toolDeck designerDraw the deck. Get the framing plan, materials list and cut list.
- CalculatorDeck joist calculatorHow many joists, how long, for any deck size.
- GuideSteel vs timber framesCost, life, span and when each one makes sense.
- GuideAluminium deck framingLow decks, pedestals and what aluminium spans.
- GuideH3 or H4 treated pineWhich parts of the frame need H4.
- GuideHow to build a deck frameSet-out, footings, bearers, joists, in order.
- GuideDeck permits by stateWhen a deck needs approval, state by state.
- GuideJoist spacing for compositeThe long version of the chart above.
Where these span figures come from
Every span here is at or under the frame maker’s own published figure for that size and load. Timber rows sit at or under published MGP10 figures. Commercial rows use a 4 kPa floor load. When a maker publishes nothing for a size, we leave it out.
Check these yourself
- The frame maker’s current span table for your exact section.
- Heavy loads: spas, planters, stone, boards over 40 kg/m².
- Wind, soil and footings for your site.
- Your state’s permit rules, and a structural sign-off where the deck needs one.
The makers’ documents
Checked against these documents on .
Treated pine MGP10
- TerraFrame Installation Guide & Span Tables (MGP10)Woodhouse
- Deck Joist and Deck Bearer Span Tables (T3 Green MGP10)Joists V4, bearers V3 · Hyne Timber
Spantec Boxspan
- Boxspan Residential Design GuideFebruary 2026 edition · Spantec Systems Pty Ltd
- Boxspan Commercial Design GuideFebruary 2026 edition · Spantec Systems Pty Ltd
InfraBuild DuraGal
- DuraGal Flooring System Technical Information Guide2022 · InfraBuild Steel Centre
Clickdeck
- Clickdeck Span TableALU261223 · Exolux Pty Ltd (Clickdeck)
Futurewood CleverDeck
- Aluminium Joist/Bearer Span TablesV1, June 2024 · Futurewood Pty Ltd
Deck span questions
How far can a 90 × 45 joist span?
Up to 1,250 mm at 450 mm centres on a home deck, in MGP10 treated pine. At 400 mm centres it’s 1,350 mm. 90 × 45 isn’t rated for commercial decks here.
How far can a 140 × 45 joist span?
Up to 2,050 mm at 450 mm centres on a home deck, and 2,200 mm at 400 mm centres. On a commercial deck at 450 mm centres it drops to 1,000 mm.
What joist spacing do I need for composite decking?
Whatever your board’s install guide says. Of the ranges we list, 450 mm is the most common for home decks and 400 mm is next. Commercial decks usually need 300 or 350 mm.
What is load width on a bearer span table?
It’s the strip of deck one bearer carries. A middle bearer carries half the gap on each side, so its load width is the gap between bearers. An edge bearer carries half a gap plus the overhang.
Do steel joists span further than timber?
A little, size for size. A Boxspan B150-16 spans 2,300 mm at 450 mm centres, against 2,050 mm for a 140 × 45 pine joist. Steel’s bigger wins are straightness and life.
Can I use these span tables for a commercial deck?
Switch the tables to Commercial. They’re worked out for a 4 kPa floor load. Commercial work usually needs a structural sign-off for the whole deck anyway.
Span tables help you plan and price a deck. They aren’t a plan sign-off.