🚪 Garage Door Header Size Calculator
Find the correct beam size for your garage door opening — enter span, load type, and lumber species for instant results.
| Door Width | Total Span (+ bearing) | Beam Size | Ply Count | Notes |
|---|---|---|---|---|
| 8 ft | 8 ft 7 in | 3-2x10 | Triple | Most common single door |
| 9 ft | 9 ft 7 in | 3-2x10 | Triple | Non-standard single door |
| 10 ft | 10 ft 7 in | 3-2x12 | Triple | Wide single / RV access |
| 12 ft | 12 ft 7 in | LVL 3.5x9.5 | Single LVL | Consider LVL here |
| 16 ft | 16 ft 7 in | LVL 3.5x14 | Single LVL | Standard double door |
| 18 ft | 18 ft 7 in | LVL 3.5x16 | Single LVL | Wide double door |
| 20 ft | 20 ft 7 in | LVL 5.25x16 | Wide LVL | RV / large double |
| Load Type | Live Load | Dead Load | Total (psf) | Multiplier Used |
|---|---|---|---|---|
| 1-Story Residential (roof only) | 20 psf | 15 psf | 35 psf | 1.0x |
| 2-Story (floor + roof) | 40 psf | 25 psf | 65 psf | 1.85x |
| 1-Story + Attic Storage | 30 psf | 20 psf | 50 psf | 1.43x |
| Light Commercial | 50 psf | 20 psf | 70 psf | 2.0x |
| High Snow (>30 psf, add-on) | +15 psf | — | +15 psf | +0.43x |
| Clear Span | Min Depth (2-ply) | Min Depth (3-ply) | Metric Span | Recommendation |
|---|---|---|---|---|
| Up to 4 ft | 2x6 | 2x4 | Up to 1.2 m | 2-ply 2x6 typical |
| 4 – 6 ft | 2x8 | 2x6 | 1.2 – 1.8 m | 2-ply 2x8 typical |
| 6 – 8 ft | 2x10 | 2x8 | 1.8 – 2.4 m | 3-ply 2x8 minimum |
| 8 – 10 ft | 2x12 | 2x10 | 2.4 – 3.0 m | 3-ply 2x10 preferred |
| 10 – 12 ft | Not recommended | 2x12 | 3.0 – 3.7 m | Use LVL or PSL |
| 12 – 16 ft | — | — | 3.7 – 4.9 m | LVL required |
| 16 – 20 ft | — | — | 4.9 – 6.1 m | LVL/PSL/Glulam required |
The upper beam of Garage Door, commonly called Header, is simply the horizontal wood that rests above the opening of the door. It binds the two vertical posts on both sides. Picture it as the highest part of the frame.
In typical garage walls one uses this structure around car gateways, and it ensures the right support, because the whole building depends on it to stay stable up.
Garage Door Header: What It Is and How to Choose One
To determine the right measure of Garage Door Header, one must consider chiefly the weight of live and dead loads, that press down on the beam. The most common home Garage Doors sit on vertical posts, hence windy forces usually hit those posts and the main posts more than the Header itself. Although, in some regions one requires engineer approval for Headers of Garage Doors, when the wall bears structural load.
Hiring an engnieer to specify the Header and frame detail is a wise step for calm.
Because the frame of the opening for the door, the main post, the jack post and the short posts all contribute too the stability. In any house, garage or building, windows and doors always require the right frame inside the bearing wall. One can extend the Header down until the opening in the garage, what helps to reduce vibration and bending during the upper door parts twist and move.
The choice of materials matter a lot. Some years ago, double 2×12-beams were the usual solution for upper door beams until 18 feet. Currently, LVL-beams always more commonly replace them.
They save time in the construction, especially for average openings of 7 feet high. LVL beams already have 1 3/4 inches of thickness, so on 2×4-walls you simply tie two of them without needing the half gap, that traditional 2x-Headers require. Many 2×12-Headers bend broadly over time, hence LVL beams are the better option, if the money allows.
For 16-foot Garage Door at the gable end wall, one option is triple 2×12-Headers, if the roof has a non-bearing ridge board. Another way is to use double 12-inch LVL beams. Headers above Garage Doors, that back floor up, must match the size according to the IRC table R602.7(1).
Around 14 inches of space above the Garage Door opening tends to be required for the upper door devices. The support for the door frame is also important, and up and along every side.
Decay can become a real problem. Water damage appears, when there is no flashing and water flows into the wooden base under the Header. One homeowner found, that his Header from two 2×12 boards had a rotting section outside, while it still backed part of the second floor.
Cutting the top or bottom of a Header widely weakens it and requires engineer rating. And here is something, that one easily misses, the Header must be fully flat. Even three inches of slope across an 8-foot beam stops theGarage Door from working correctly.
