framing
I want to replace a 20" W window ( 20 5/8" rough) with a 36" (rough) window. I want it to be as close to the ceiling as possible. It is a single story house with 2×4 studs on 16" centers. It has a double top wall plate.
What is the smallest size header I can use. The new window is 36" W x 12" H. (rough).
If you can nail down through the top plate (e.g. before the second top plate is installed) then 3 12d nails is standard for 2x6 framing. For nailing the cripple into the header, toenailing should be fine, but I'd use 12d glue coated framing nails (greenish nails). Save the 8d nails for attaching sheathing.
Note, this is just personal experience, your local codes may require otherwise. It doesn't hurt to ask your building inspector what they require.
No, no and again NO. Not the way you suggest it, anyway.
This is an exterior wall. It is therefore a load bearing wall. Those two 2x4s (called jack studs) support the header over the window.
The weight of the rest of the house above the window is protected by the header, which in turn transfers the force to the two jack studs (as in they jack up the house) carry that weight to the underlying structure. If you remove one of the jack studs, too much force may be transferred to the other one, causing it to bow or even possibly fail. Either scenario translates to having weight of the wall above the house coming to rest on the window itself - and that is a BAD THING (TM).
If you wish to restructure for a larger opening properly, you must open the wall up further and relocate the king and jack studs, and install a longer (and possibly wider) header as well. Otherwise you can cause many tens of thousands of dollars of damage to your house.
Do not fiddle lightly with structure.
Best Answer
it depends on a lot of things:
1) dead load above 2) live load (do you get lots of snow, rain, etc.) 3) wall finish (for practical reasons you may have difficulty changing the header on a stucco wall, which is what it looks like from the cement stains on the interior of the sheathing boards) 4) material. steel is much stronger than wood. spruce is stronger than pine.
in a 2 x 4 wall, you can do a double header construction with a 5/8" ply liner between them as a spacer. given this, the fact that you are increasing the span from 20" to 36", then the span will be almost twice what was there before, but its still only 36". generally, you need a 2x6 double header minimum for just about any scenario, so if you are worried about it, go to a double 2x8. here in ontario, lintels under 2x8 are not permitted (table a-12), but your span is so small it doesn't even fit the minimum requirements. just use a doubled 2x8. its overkill, but thats the best way to build anything.