Built Up Framing Headers
When framing the window and door openings, during new
home construction, there are a couple of ways to create the header.
The header is the framing support that holds up the floor or roof above it. Normally the window or door header will be the thickness of the wall width. If the wall is 2 x 6, the header is going to be 5 1/2 inches wide or the same thickness as the width of the 2 x 6 wall.
Carpenters and framers for years have been building their own window and door headers by doubling or tripling up 2 x framing lumber as a replacement for solid wood headers. For example, nailing two 2 x 6 pieces of lumber together with a piece of 3/8" plywood located in the center, would create a replacement for a solid 4 x 6 header.
As a warning to builders all over the country, if you choose to continue this practice, you could be removing built up window and door headers if the plans specify a solid window or door header. For example if your plans or blueprints, specify using a 6 x 6 door header and a structural shear wall, I would advise you to use a solid 6 x 6 unless the structural engineer approves using a built up header.
Here's a tip to anyone who's going to build their own window or door headers, using the built up header method. If you noticed, I used a piece of 3/8" plywood instead of a piece of half inch plywood, for the center of my built up header in the paragraphs above.
If you do the math, a 2 x 6 is normally an inch and a half wide and if we add two of them together, this would be 3 inches. It would make perfect sense to use a piece of half inch plywood. I've noticed that half inch plywood makes the total width of my built up header a little larger than I would expect. These headers often seem to be 3 5/8" wide. This creates a problem, with the interior or the exterior, depending on which side you choose to stick the extra eighth of an inch into.