Deck Span Table FAQs

A deck span table is a published table that shows the maximum allowable span for a joist, bearer or beam under stated loading, spacing, support and use conditions.

A deck span chart is a visual or simplified way of presenting span-table information so users can compare joist spans, bearer spans, spacing, FLW and product options more quickly.

FLW means floor load width. It is the width of floor or deck area that loads onto a bearer or beam. A larger FLW usually reduces the allowable bearer span.

Joist span is the distance a joist spans between supports. Bearer span is the distance a bearer or beam spans between posts, piers or other supports.

No. SpanFinder is for preliminary comparison. Final selections should be checked against the current manufacturer span tables and the actual site conditions.

A deck joist span table shows how far a joist can span between supports for a stated joist size, material, spacing, load and span type.

It depends on the joist product, joist spacing, decking dead load, deck height, live load and whether the joist is single span or continuous span.

Deck joist spacing is the centre-to-centre distance between adjacent joists. Common search terms include 300 mm, 400 mm, 450 mm and 600 mm joist spacing.

Often yes, because each joist carries less tributary width, but the result must be checked in the published span table.

No. Joist tables and bearer tables check different structural roles and usually use different input columns.

A deck bearer span table shows how far a bearer or beam can span between posts, piers or supports for the stated FLW, load case and span type.

Bearer span is the distance between supports under the bearer, such as posts, piers, columns or walls.

Bearer spacing depends on the joist span layout and deck structure. Bearer spacing is not the same as bearer span between posts.

Post spacing depends on the bearer product, bearer span table, floor load width, deck loads and support conditions.

Bearers carry load from a width of deck. FLW is the table input that represents that loaded width.

Floor load width is the width of deck or floor area that contributes load to a bearer or beam.

Not always. For a simple internal bearer carrying joists from both sides, FLW may relate to half the joist span on each side. For an edge bearer it may relate to one side only.

For preliminary estimating, add the tributary joist length feeding into each side of the bearer. Edge bearers usually carry one side. Internal bearers may carry load from both sides.

A larger floor load width means the bearer carries load from a wider strip of deck, so the allowable span generally reduces.

For preliminary comparisons, rounding up to the next available published FLW column can be conservative, but final design must follow the source table rules.

450 mm centres is common for many deck layouts, but the correct spacing depends on the decking board, joist product and span-table requirements.

For preliminary estimating, divide the deck width by the joist spacing and add one outside joist. Allow for trimming, double joists and perimeter framing separately.

Yes. Closer spacing usually means each joist carries less load, but the correct maximum span still comes from the relevant span table.

No. It is a quick spacing calculator only and does not include waste, blocking, trimming, fixing requirements or detailed framing rules.

Deck post spacing is the distance between posts or piers supporting a bearer. It often becomes the bearer span checked in the span table.

Usually, if posts directly support the bearer, the distance between posts is the bearer span. Complex layouts may need engineering review.

For a simple straight bearer line, divide the bearer length by your chosen maximum spacing and add one end post.

Closer posts reduce bearer span, which may allow a smaller bearer, but footing design and practical layout still matter.

No. It estimates post count and spacing only. Use the live span finder or source bearer tables for member selection.

Dead load is the permanent weight of the structure and finishes, such as decking boards, framing, sheeting or other fixed materials.

Live load is the imposed load from people, furniture and use of the deck or floor area.

Roof load width or RLW is a roof-framing term describing the width of roof load carried by a member. It is different from FLW but appears in similar span-table workflows.

NS often means no suitable span or not suitable in that table context, but the exact meaning should be checked against the source document.

Some sources do not match every input exactly. The tool can show conservative or adapted rows where useful, but labels them so they are not mistaken for exact matches.