Dear Preppers and Survivalists,
I figured I should talk about window headers, window sills, and cripples before going on to the roof.
All windows have a 'rough opening.' This opening is the required opening that needs to be in the wall before the window is mounted in the wall. The rough opening measurements can be found written in the window's installation instructions.
Now, we are going to have eight windows, two on each wall for ventilation.. Two big windows require a ??X?? rough opening and the other windows require a 14 inch by ?? inch rough opening.
So, why do you need a header?
Remember, the top plate (the double 2X4s) acts as support for the roof. When you cut an opening in the wall that spans between studs, you have to replace that missing support. The header acts as that support.
Now, needless to say, the bigger the opening, the bigger the header.
I talked to some former carpenters at work and they said a doubled 2X6 would be fine for this short of a header. Plus, one remarked: "It's a chicken coop. If you really wanted, you could probably use double 2X4s as a header."
Now, if you were putting in a picture window in your home, you would need a much thicker header, maybe a 2X10 or 2X12, maybe even an engineered wooden header or a steel beam header for a really large window.
OK, back to building a small building.
Wow, what a sentence!
Needless to say, you want to know why I covered up the windows rough openings with the OSB sheathing.
It's a lot easier to cover up the opening, and cut it out later, than cut the sheathing then attach it to the 2X4 wall.
I almost forgot.
The cripples, those short pieces of 2X4 above the headers and below the window sills, act as a place to secure the sheathing to the wall. They basically 'fill in' for the studs that I removed for the window opening.
Just so you know, they're called cripples because they are 'broken' studs.
Making the Headers
Just like I said earlier, we used 2X6s as headers. Since they are going to support some of the weight of the roof, I doubled them.
The former carpenters said I could place a piece of plywood between the double 2X6s to fill in the gap.
I could nail the two 2X6s together and make sure the header is even with the inside edge of the stud.
I could do it the way I described.
Lastly, one of the guys said that I could also place a cripple between the header and the window sill for added, really added, support for the roof. As you can tell, I didn't do that.