Sizing a Header for a New Window Opening

Measure the width of the planned opening before anything else, because the span decides every other choice about the header. On a new window in a bearing wall, the roof or the floor above pushes down through the studs, and the header is the beam that carries that push around the hole, and austin new windows le mistral houston sets the order of those checks deliberately: span, then load path, then glass. A new window in Austin, TX gets the same arithmetic as any other wall: how wide, how much sits on top, how far the weight travels to the ground.

What the header actually carries

A header takes the load from the studs it interrupts and hands it to the jack studs on each side. Those jacks sit on the king studs, and the king studs run full height to the plate. A narrow opening for a double hung unit in a wall under a light roof may need only a pair of doubled framing boards on edge. A wide picture window or a run of three casement units in a wall that also carries a second floor needs an engineered beam, sized by whoever stamps the plans.

Doubled lumber or an engineered beam

Doubled lumber is quick to cut and easy to fit in a thin wall, but it only reaches so far. Past a certain span the boards sag and the sash binds. Laminated veneer lumber holds a flatter line over longer spans and does not twist as it dries. In older houses around Hyde Park and Clarksville the walls are often two by four, so the beam has to be chosen to fit that depth or the wall has to be furred out.

Shoring while the wall is open

Before any stud is cut, temporary posts or a stud wall go up a short distance inside, carrying the plate. The wall is only opened once the load is on the shoring. The header goes in, the jacks are nailed to it, and only then do the shores come down.

Window choice follows the opening

A header sized for a vinyl window or a fiberglass window is the same header an aluminum window or a clad window would need, but the rough opening changes with the frame. A bay window or a bow window projects past the wall and brings its own seat board and roof, so its framing is closer to a small addition than to a flat opening. Insulated glass units in these larger frames also weigh more, and the sill needs solid blocking under it.

Checking the finished opening

With the header set, hold a long level across the top and measure to the sill at both ends. The two numbers should match within an eighth of an inch. An opening out of square by more than that fights the window for the life of the house, and the sash will rub in the corner that closes.