Ontario Building Code Span Tables: Joists, Rafters, Beams and Lintels

Which span table to use

This is our own index of the tables, not a copy of any table.

Before you read any table: does it apply?

The floor joist, beam and lintel spans apply only where the floor serves residential areas, or carries no more than the residential live load from Table 4.1.5.3. (9.23.4.1.OBC Div. B 9.23.4.1. Application(1) Spans provided in this Subsection for joists, beams and lintels supporting floors shall apply only where (a) the floors serve residential areas as described in Table 4.1.5.3., or (b) the uniformly distributed live load on the floors does not exceed that specified for residential areas as described in Table…). Floors with heavier loads are designed under Subsection 4.1.3. Spans for floor joists chosen any other way must still meet the uniform load and vibration criteria the tables are based on (9.23.4.2.(2)OBC Div. B 9.23.4.2. Spans for Joists, Rafters and Beams(1) Except as required in Sentence (2) and Article 9.23.14.10., spans for wood joists and rafters shall conform to the spans shown in Span Tables 9.23.4.2.-A to 9.23.4.2-G for the uniform live loads shown in the Tables. (See Article 9.4.2.2.) (2) Spans for floor joists that are not selected from Span Tables…).

How to read a joist or rafter table

Every joist and rafter table is read the same way:

1. Commercial designation (species group). Douglas Fir and Larch, Hem and Fir, Spruce, Pine and Fir (SPF), and Northern species. The notes list which species fall in each group. Most Ontario lumber is SPF.
2. Grade. Select Structural, No. 1 and No. 2 (grouped together), No. 3, and so on. Use the grade stamped on the lumber.
3. Member size. 38 × 89 mm up to 38 × 286 mm (2x4 to 2x12 in trade sizes).
4. Spacing. 300, 400 or 600 mm on centre.
5. The case or load. For floor joists, Table -A is split into general cases with strapping, with bridging, and with both. Strapping and bridging must meet 9.23.9.4.OBC Div. B 9.23.9.4. Strapping, Bridging, Furring and Ceilings in Span Tables 9.23.4.2.-A and 9.23.4.2.-B)(1) Except as permitted by Sentence (5), where strapping is specified in Span Table 9.23.4.2.-A, it shall be (a) not less than 19 mm by 64 mm, nailed to the underside of floor joists, (b) located not more than 2,100 mm from each support or other rows of strapping, and (c) fastened at each end to a sill or header. (2)…: at least 19 × 64 mm, in rows not more than 2,100 mm apart, and a panel ceiling attached directly to the joists can replace strapping. For roof joists and rafters, pick the section for your specified roof snow load, which you calculate under 9.4.2.2.OBC Div. B 9.4.2.2. Specified Snow Loads(1) Except as provided in Sentences (2) and (4), specified snow loads shall be not less than those calculated using the following formula: S = C_bS_s + S_r where S = specified snow load, C_b = basic snow load roof factor, which is 0.45 where the entire width of a roof does not exceed 4.3 m and 0.55 for all other… using SB-1 climate data.

The value in the cell is the maximum span. If your span is longer, go up a size, reduce spacing, choose a stronger grade or species, or add a support.

How to read a built-up beam table

Built-up beams are layers ("plies") of 38 mm lumber nailed or bolted together on edge. The tables are read by:

1. Floors supported. Table -H for 1 floor, -I for 2, -J for 3.
2. Member depth. Each table has sections for 38 × 184, 38 × 235 and 38 × 286 mm members.
3. Species and grade.
4. Supported length. Half the sum of the joist spans on both sides of the beam. Straight interpolation is allowed between rows.
5. Number of plies. 3, 4 or 5 members.

The notes matter. Spans are clear spans, so add two bearing lengths for the member length. Where the floor has a concrete topping of not more than 51 mm, multiply the span by 0.8. In Table -H, bearing is 76 mm for most beams and 114 mm for 3-ply beams with a supported length over 4.2 m, which takes precedence over the general 89 mm in 9.23.8.1.OBC Div. B 9.23.8.1. Bearing for Beams(1) Beams shall have even and level bearing and the bearing at end supports shall be not less than 89 mm long, except as stated in the notes to Span Tables 9.23.4.2.-H to 9.23.4.2.-K. ..

Our worked lookup

A bungalow has a centre beam with floor joists spanning 3.6 m on each side. The beam is three plies of 38 × 184 mm SPF No. 1 or No. 2, and it supports one floor.

• Supported length: (3.6 + 3.6) / 2 = 3.6 m.
• Table: 9.23.4.2.-H (not more than one floor), 38 × 184 mm section, SPF No. 1 and No. 2, 3.60 m row, 3-ply column.
• Maximum clear span: 2.63 m between posts.
• Bearing: 76 mm at each end, since a 3-ply beam needs 114 mm only above 4.2 m supported length.

If the posts need to be farther apart, try 4 plies or a deeper member in the same table. The joist, rafter and beam span method in our Calculation Lab has more practice lookups.

Building the beam

A built-up wood beam must use members at least 38 mm thick on edge (9.23.8.3.OBC Div. B 9.23.8.3. Built-up Wood Beams(1) Where a beam is made up of individual pieces of lumber that are nailed together, the individual members shall be 38 mm or greater in thickness and installed on edge. (2) Except as permitted in Sentence (3), where individual members of a built-up beam are butted together to form a joint, the joint shall occur over…). Butt joints occur over supports, or for continuous beams within 150 mm of certain quarter points, with no more than one joint per member in a span. The plies are nailed with a double row of nails at least 89 mm long, rows not more than 450 mm apart, or bolted with 12.7 mm bolts at not more than 1.2 m.

Lintels

Lintels over openings in loadbearing walls use Table 9.23.4.2.-L and Tables 9.23.12.3.-A to -D, for residential buildings with studs larger than 38 × 64 mm, supported joists not over 4.9 m and trusses not over 9.8 m (9.23.12.3.OBC Div. B 9.23.12.3. Lintel Spans and Sizes(1) Spans and sizes of wood lintels shall conform to the spans shown in Span Tables 9.23.4.2.-L and 9.23.12.3.-A to 9.23.12.3.-D (a) for buildings of residential occupancy, (b) where the wall studs exceed 38 mm by 64 mm in size, (c) where the spans of supported joists do not exceed 4.9 m, and (d) where the spans of…). In 38 × 64 mm stud walls, lintels must be 50 mm deeper than the tabled size and not longer than 2.24 m.

Steel beams

Steel beams with laterally supported top flanges use Table 9.23.4.3. for floors and Tables 9.23.4.3.-A to -J where they carry a roof and floor (9.23.4.3.OBC Div. B 9.23.4.3. Steel Beams(1) The spans for steel beams with laterally supported top flanges shall conform to Table 9.23.4.3. for floors and Span Tables 9.23.4.3.-A to 9.23.4.3.-J for roofs and floors. (See Note A-9.23.4.3.(1)) (2) Beams described in Sentence (1) shall at least meet the requirements for Grade 350 W steel in CSA G40.21…). They must be at least Grade 350W steel. Joists bearing on the top flange at 600 mm or less, with wood strips nailed beside the flange, count as lateral support.

How to look it up yourself

In Division B, Part 9 of the 2024 Compendium, go to Section 9.23 "Wood-Frame Construction". Search terms that appear in the code:

• "Spans for Joists, Rafters and Beams" (9.23.4.2.)
• "Maximum Spans for Floor Joists"
• "Built-up Floor Beams"
• "Supported length means"
• "Lintel Spans and Sizes" (9.23.12.3.)

Open 9.23.4.2. in the code viewer to jump to each table.

BCIN exam angle

Span lookups appear on the House and Small Buildings exams, often with a supported length you must work out first. Read the free House chapter on wood-frame and steel stud construction or the Small Buildings chapter on foundations, framing and structure, then practise on the House exam and Small Buildings exam pages.

Related pages

• Deck building code in Ontario
• Ontario Building Code footings
• Ontario Building Code Part 9 overview