What is a Wind Beam in Structural Engineering?

Has your engineer specified a wind beam in your external wall? What is a wind beam and why is it there? Do you even need it??

When wind blows on the walls of a structure, it is primarily the job of the vertical studs to keep the wall upright and transfer wind loads into the rest of the structure.

However, in some places, where the roof and ceiling is very high,  wall studs are not strong enough to handle the applied wind loads.

That’s where wind beams come in.

Typical areas where wind beams may be required include:

• Raked ceilings in gable roofs where an unsupported wall stud would have to be very tall. The taller the wall studs, the thicker the wall has to be. By specifying a wind beam, your engineer has reduced the span of the studs so they can be normal-sized. The wind beam also helps transfer wind loads to the rest of the building.

Figure 1: Example of a wind beam (WB1) at the tall sections of the gable wall. Columns (C1/C2) are required at each end to support the beam.

• You might see a wind beam specified beside a stair void or a double-height void. Where the studs are not supported by the floor (because there is no floor!), a wind beam is used to reduce the span of the studs. Similar to the example above, a wind beam across the stair void/double-height void supports the studs and transfers the loads sideways to the floor.

Figure 2: Example of a wind beam (WB1) under a window in a stairwell. Columns (C1) at each end can support the floor beam.

• In houses with high ceilings, sometimes the beams over windows and doors have a secondary function – to take the wind loads on the door and distribute them sideways. You don’t want your door to rattle and shake every time you open and close the door do you? When lintels also act as wind beams, we tend to make the beams wider so they have more strength out-of-plane – which is ‘engineer speak’ for sideways loads.

How are wind beams designed?

Technically speaking, we have a few options. Wind beams can be designed using a beam spanning around its major axis (the strong way – Type 1 in the sketch) BUT beams in this direction are often a lot wider than the rest of the wall. So, the beam is going to stick out of the wall awkwardly, and a homeowner probably isn’t going to be very happy.

Type 2 is just a whole heap of top plates stacked on top of each other. Not very effective use of the timber but at least the wind beam is contained within the width of the wall.

Figure 3: Extract from Hyne Timber design software depicting 3 types of wind beams.

Type 3 is our preferred type of wind beam. The wind beam can be hidden nicely within a finished wall so when it’s complete, no one will even know.

BUT, spanning our beam around its weak axis (minor axis bending) is still not very economical. It is the best case in a bad scenario.

Once a type of wind beam is chosen, there are 4 main factors engineers need to consider when designing a wind beam.

1. Is the wind beam strong enough to carry the loads applied to it?
2. Will the beam deflect too much? This is important because if the beam deflects too much, cracking may appear in windows, trims, or finishings and doors may become “sticky”.
3. How is the beam supported? Typically, wind beams are supported by columns or studs at each end. Your structural engineer also needs to check these supporting elements to ensure they can carry the load from the wind beam to the rest of the building.
4. Once the wind beam has directed wind loads to the structure, does the structure have the required bracing in place?

Once all 4 factors have been considered, an engineer can often design a wind beam to be hidden within walls and finishings such that you wouldn’t even know they’re there.

Additional note: In some applications, a wind beam may be avoided by using larger or more closely spaced wall studs. In these cases, an engineer may use their best judgement to determine which option is easier to construct and most cost effective.

So, that’s a little bit about wind beams, why engineers use them and what to look out for.

Now, if your builder decided to skip installing a wind beam that has been specified in your plans, then some alternative way of supporting the studs is required. Did they go with bigger studs?

One last thing: Wind beams are just like a lot of other beams in construction. They need to be designed, checked and installed appropriately.

Got a problem with a wind beam?  You might need the help of a local structural engineer!