Over most garage doors there are two separate members: a header in the wood-framed wall that carries the roof and any floor above, and a steel angle lintel in the brick that carries only the veneer. The header becomes a steel beam when the opening is wide, there's a room over the garage, or there isn't enough depth for wood. Under the 2024 Ontario Building Code, steel beams carrying a roof and one floor are sized from Tables 9.23.4.3.-A to -J. In the table for brick veneer and a 1.0 kPa roof snow load, for example, a W250x39 reaches 5.04 m, enough for a 16 ft (4.88 m) door, when the supported roof and floor lengths are each 2.4 m.
The lintel that holds up the brick over a garage door has its own guide: steel lintels over garage doors. This post is about the structural header behind it.
Header vs lintel: what each one carries
A typical attached garage front in Ontario is a wood stud wall with brick or stone veneer outside. Across the door opening:
- The header sits in the stud wall and carries the roof framing, the wall above and, if there's a bonus room or bedroom over the garage, a floor. It brings that load down to the studs or posts at each side of the opening.
- The veneer lintel is a steel angle under the brick. It carries the masonry above the opening and nothing else.
When people ask for a "steel beam for a garage door", they usually mean the header, because that's the member that grows with the load. In some houses, a single W-beam with a plate welded to its bottom flange does both jobs, carrying the framing on the beam and the brick on the plate.
When a garage door header becomes a steel beam
Wood headers and LVL handle many single garage doors. Steel tends to take over when:
- There's a room above. A floor over the garage adds floor dead and live loads, plus the wall and roof above that, onto the header.
- The opening is wide. Double doors of 16 ft or 18 ft, or a wider-than-standard opening for a large vehicle.
- Depth is limited. The door's head height, the track and the opener need space. A shallow steel section can leave room that a deeper wood member would take.
- Two singles become one double. Removing the centre pier roughly doubles the header span and concentrates the load at the two outside supports.
- A girder truss or beam lands on the header. Concentrated loads are where steel and an engineered design come in.
What the Ontario code covers for garage headers
Part 9 of the 2024 OBC (O. Reg. 163/24, Division B) gives you three families of tables, and it matters which one applies:
| Member | Code reference | What it covers |
|---|---|---|
| Wood headers (the code calls them lintels) | Article 9.23.12.3, Span Tables 9.23.4.2.-L and 9.23.12.3.-A to -D | Residential buildings, supported joist spans up to 4.9 m, truss spans up to 9.8 m |
| Steel beams carrying a roof and one floor | Article 9.23.4.3, Tables 9.23.4.3.-A to -J | Beams supporting exterior stud walls with brick veneer, or interior walls or exterior walls with siding, for specified roof snow loads of 1.0 to 3.0 kPa |
| Steel beams carrying veneer and a stud wall only | Article 9.20.5.2, Table 9.20.5.2.-C | Beams supporting masonry veneer, a wood stud wall and a limited roof load, with a steel column at each end |
The steel beam tables in Article 9.23.4.3 are the closest thing the code has to a "steel header span table". They're simple-span tables with conditions, not a design method for every garage.
Reading the roof and floor tables for a garage opening
Tables 9.23.4.3.-A to -J are split by veneer (brick, or siding and interior walls) and by the specified roof snow load at the site. Each table lists W-shapes against two inputs:
- Supported roof length: half the sum of the roof framing spans on both sides of the beam.
- Supported floor length: half the sum of the floor framing spans on both sides of the beam.
Here are selected rows from Table 9.23.4.3.-A (brick veneer, 1.0 kPa snow load) and Table 9.23.4.3.-I (brick veneer, 3.0 kPa snow load). Spans are maximum spans in metres.
| Section | 1.0 kPa, roof 2.4 / floor 2.4 | 1.0 kPa, roof 6.0 / floor 3.6 | 3.0 kPa, roof 2.4 / floor 2.4 | 3.0 kPa, roof 6.0 / floor 3.6 |
|---|---|---|---|---|
| W200x27 | 3.80 | 3.33 | 3.40 | 2.81 |
| W250x33 | 4.71 | 4.12 | 4.21 | 3.47 |
| W250x39 | 5.04 | 4.41 | 4.51 | 3.72 |
| W310x39 | 5.66 | 4.96 | 5.06 | 4.18 |
| W310x45 | 5.96 | 5.22 | 5.33 | 4.40 |
| W360x39 | 6.01 | 5.27 | 5.38 | 4.44 |
Source: 2024 Ontario Building Code, Division B, Tables 9.23.4.3.-A and 9.23.4.3.-I.
Two things stand out. First, the snow load matters: the same W250x39 drops from 5.04 m to 4.51 m between the two tables. Your designer takes the snow load for your municipality from the code's climatic data, so don't pick a table by guesswork. Second, a long roof or a deep room behind the beam cuts the span quickly. For a 16 ft door with a 6.0 m supported roof length and 3.6 m supported floor length at 1.0 kPa, the W250x39 no longer works and a W310x39 (4.96 m) is the first listed section in this excerpt that does. Remember too that the beam spans between its supports, which is more than the door's clear width.
The tables also come with design assumptions, set out in the code's explanatory notes:
- Simple spans with a laterally supported top flange. The framing above has to brace the top of the beam.
- Brick load without arch action. The brick tables assume a full storey of brick with windows above, so the brick is treated as a uniform load along the beam.
- Deflection limits. Span/600 for the brick tables (brick plus live load) and span/360 on live load for siding walls.
Article 9.23.4.3 also requires beams sized from these tables to meet at least the requirements for Grade 350W steel in CSA G40.21. If the W-shape names are new to you, see how to read steel beam sizes, and for the floor-only tables, our steel beam span tables guide.
Garage details that change the beam
The table gives a section. The garage itself decides how it's built:
- Head height and door hardware. Check the door manufacturer's headroom needs for the track and opener before choosing between a deep, light beam and a shallower, heavier one.
- Flush or dropped. A beam set flush with the floor joists of a room above needs joist hangers or seats and a nailer for the framing. A dropped beam under the joists is simpler but takes height.
- Supports at each end. The load comes down at two points. Steel columns or built-up posts in the wall carry it to the foundation, and the footing under each one has to suit the load. Bearing length matters too; see steel beam bearing length.
- The brick. If the beam also carries the veneer, a plate welded to the bottom flange forms the ledge for the brick, and the steel needs corrosion protection. The code requires exterior steel beams to be shop primed with rust-inhibitive paint (Article 9.23.8.2).
- Openings above. Windows or a short band of wall between the door and the eaves affect how loads reach the beam.
When the garage header has to be engineered
The tables stop short of many real garages. Expect an engineer when:
- A girder truss, beam or post from above lands on the header
- There's more than one floor above the garage, or a cantilevered room overhangs the door
- The opening, the snow load or the supported lengths are outside the tables
- You're widening an existing opening or removing a centre pier between doors
- The beam carries brick and a floor in an arrangement the tables don't describe
Widening or altering a garage opening is a structural change to the house and needs a building permit. Our post on steel beams for home additions and exterior wall openings covers the wider family of exterior-wall projects.
Getting a garage header beam made
To quote a garage door beam accurately we need the beam size from your drawings or engineer, the length between supports, any welded plate for the veneer, holes for nailers or connections, and the posts and base and cap plates if you need them too. If you don't have a design yet, engineering services are available for projects that need them.
Send us your drawings or opening details for a quote. We fabricate W-beams with welded plates, posts and connection plates in our CWB certified shop and deliver across the GTA and Ontario. See our steel products for beams, lintels, posts and plates.
Frequently asked questions
What size steel beam do I need for a 16 ft garage door?
It depends on what the beam carries and your snow load. In the 2024 Ontario Building Code table for a roof and one floor with brick veneer and a 1.0 kPa snow load, a W250x39 reaches 5.04 m when the supported roof and floor lengths are each 2.4 m, but a deeper section is needed as those lengths grow. Rooms above with point loads are engineered.
Is there a span table for steel garage door headers?
Not under that name. Steel beams carrying a roof and one floor are sized from Tables 9.23.4.3.-A to -J of the 2024 OBC, and steel beams carrying only brick veneer and a stud wall from Table 9.20.5.2.-C. Wood headers have their own tables in Article 9.23.12.3.
Do I need a steel beam to convert two single garage doors to one double?
Usually something stronger than the old headers, because removing the centre pier roughly doubles the span and concentrates load at the ends. Steel is common because it keeps the depth down. It is a structural alteration that needs a design and a building permit.
Can a garage door header be an LVL instead of steel?
Often, yes, for single doors and some doubles. Steel tends to win when the opening is wide, a room sits above, or the depth available between the door head and the floor or roof framing is limited.
