Ceiling Joist Span Chart

Maximum Spans for 2x4 to 2x10 Ceiling Joists by Species, Spacing and Attic Storage, With a Joist Size Calculator

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Ceiling joists carry the ceiling and whatever sits in the attic above it. The 2021 International Residential Code gives their maximum spans in two tables: R802.5.1(1) for uninhabitable attics without storage (under 42 in of headroom; 10 psf live load, 5 psf dead) and R802.5.1(2) for attics with limited storage (20 psf live, 10 psf dead), both limiting deflection to span ÷ 240. For No. 2 lumber at 16 in on centre and no storage, a 2x6 spans 16 ft 6 in (hem-fir) to 17 ft 8 in (Douglas fir-larch) and a 2x8 21 ft 7 in to 23 ft 4 in; with limited storage the same 2x6 spans only 12 ft 0 in to 13 ft 0 in. Enter the clear span, spacing, species and attic use and the Ceiling Joist Span Calculator picks the smallest size, adds the 1 1/2 in end bearing IRC R802.6 requires and counts the joists. A 14 ft span at 16 in in spruce-pine-fir needs 2x6s (2x8s with storage), 16 ft long.

Ceiling joist spans come from two tables in the 2021 International Residential Code: R802.5.1(1) for uninhabitable attics without storage (clear height under 42 in; 10 psf live load, 5 psf dead load) and R802.5.1(2) for uninhabitable attics with limited storage (20 psf live, 10 psf dead). Both limit deflection to span ÷ 240 and stop at 26 ft (note a). The figures below are for No. 2 grade lumber. Each joist end also needs at least 1 1/2 in of bearing on wood or metal (IRC R802.6).

Ceiling joist span chart — attics without storage (IRC Table R802.5.1(1))

Maximum ceiling joist span, No. 2 grade, 10 psf live load, 5 psf dead load
SpacingSpecies2x42x62x82x10
12 inDouglas fir-larch12 ft 5 in19 ft 6 in25 ft 8 inover 26 ft
12 inHem-fir11 ft 7 in18 ft 2 in24 ftover 26 ft
12 inSouthern pine11 ft 10 in18 ft 8 in24 ft 7 inover 26 ft
12 inSpruce-pine-fir11 ft 10 in18 ft 8 in24 ft 7 inover 26 ft
16 inDouglas fir-larch11 ft 3 in17 ft 8 in23 ft 4 inover 26 ft
16 inHem-fir10 ft 6 in16 ft 6 in21 ft 9 inover 26 ft
16 inSouthern pine10 ft 9 in16 ft 11 in21 ft 7 in25 ft 7 in
16 inSpruce-pine-fir10 ft 9 in16 ft 11 in22 ft 4 inover 26 ft
19.2 inDouglas fir-larch10 ft 7 in16 ft 8 in21 ft 4 in26 ft
19.2 inHem-fir9 ft 11 in15 ft 7 in20 ft 6 in25 ft 3 in
19.2 inSouthern pine10 ft 2 in15 ft 7 in19 ft 8 in23 ft 5 in
19.2 inSpruce-pine-fir10 ft 2 in15 ft 11 in21 ft25 ft 8 in
24 inDouglas fir-larch9 ft 10 in15 ft19 ft 1 in23 ft 3 in
24 inHem-fir9 ft 2 in14 ft 5 in18 ft 6 in22 ft 7 in
24 inSouthern pine9 ft 3 in13 ft 11 in17 ft 7 in20 ft 11 in
24 inSpruce-pine-fir9 ft 5 in14 ft 9 in18 ft 9 in22 ft 11 in

Ceiling joist span chart — attics with limited storage (IRC Table R802.5.1(2))

Maximum ceiling joist span, No. 2 grade, 20 psf live load, 10 psf dead load
SpacingSpecies2x42x62x82x10
12 inDouglas fir-larch9 ft 10 in15 ft19 ft 1 in23 ft 3 in
12 inHem-fir9 ft 2 in14 ft 5 in18 ft 6 in22 ft 7 in
12 inSouthern pine9 ft 3 in13 ft 11 in17 ft 7 in20 ft 11 in
12 inSpruce-pine-fir9 ft 5 in14 ft 9 in18 ft 9 in22 ft 11 in
16 inDouglas fir-larch8 ft 11 in13 ft16 ft 6 in20 ft 2 in
16 inHem-fir8 ft 4 in12 ft 8 in16 ft19 ft 7 in
16 inSouthern pine8 ft12 ft15 ft 3 in18 ft 1 in
16 inSpruce-pine-fir8 ft 7 in12 ft 10 in16 ft 3 in19 ft 10 in
19.2 inDouglas fir-larch8 ft 2 in11 ft 11 in15 ft 1 in18 ft 5 in
19.2 inHem-fir7 ft 10 in11 ft 7 in14 ft 8 in17 ft 10 in
19.2 inSouthern pine7 ft 4 in11 ft13 ft 11 in16 ft 6 in
19.2 inSpruce-pine-fir8 ft11 ft 9 in14 ft 10 in18 ft 2 in
24 inDouglas fir-larch7 ft 3 in10 ft 8 in13 ft 6 in16 ft 5 in
24 inHem-fir7 ft 1 in10 ft 4 in13 ft 1 in16 ft
24 inSouthern pine6 ft 7 in9 ft 10 in12 ft 6 in14 ft 9 in
24 inSpruce-pine-fir7 ft 2 in10 ft 6 in13 ft 3 in16 ft 3 in

Worked example: 14 ft span, 16 in on centre, spruce-pine-fir No. 2

Frequently asked questions

How far can a 2x6 ceiling joist span?

Under 2021 IRC Table R802.5.1(1), for an attic without storage, a No. 2 2x6 at 16 in on centre spans 17 ft 8 in in Douglas fir-larch, 16 ft 11 in in southern pine or spruce-pine-fir and 16 ft 6 in in hem-fir. At 24 in the same joists span 13 ft 11 in to 15 ft. If the attic has limited storage, Table R802.5.1(2) cuts that to 12 ft 0 in to 13 ft 0 in at 16 in.

How far can a 2x8 ceiling joist span?

A No. 2 2x8 at 16 in on centre spans 21 ft 7 in to 23 ft 4 in under an attic without storage, and 15 ft 3 in to 16 ft 6 in under an attic with limited storage, depending on species (2021 IRC Tables R802.5.1(1) and (2)).

What is the difference between the two ceiling joist tables?

Table R802.5.1(1) is for uninhabitable attics without storage — clear height under 42 in, designed for a 10 psf live load and 5 psf dead load. Table R802.5.1(2) is for uninhabitable attics with limited storage — 42 in or more of clear height, or trusses that leave a 42 × 24 in space — designed for 20 psf live and 10 psf dead (IRC Table R301.5). Both limit deflection to span ÷ 240.

How long should ceiling joists be?

The span in the tables is the clear distance between supports. Each end also needs at least 1 1/2 in of bearing on wood or metal (3 in on masonry) under IRC R802.6, so buy the next even foot up from the span plus 3 in. A 14 ft span needs 14 ft 3 in of joist, so 16 ft stock.

Can ceiling joists span more than 26 feet?

The IRC tables stop at 26 ft (note a). Longer spans need engineered lumber, a beam or bearing wall partway across, or trusses designed for the span.

Framing the rafters too? The rafter span chart lists rafter spans by size, spacing and load.

Need the whole roof at once? The free roofing calculator works out roof area, squares, shingle bundles, underlayment, drip edge, ridge cap and installed cost from one set of measurements.