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Old 05-28-2008, 05:21 PM   #1
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Max span for 4x8 header?

OK, I'm sure I've got a no-brainer for you construction experts:

Background: I have a single-story ranch house, built in '87, so it has 2x4 exterior walls. No interior walls are bearing, as there are trusses spanning the entire width of the house. So, all exterior walls are load bearing.

In the remodel project I'm doing (for which I'm hiring a professional framer), I want to move a window & an exterior door. The current window is 4' wide, and the new window will be 3'6" wide. The current door is 6' wide, new door will be 5' wide. Both will be moving about 1.5 feet down the wall (no, not vertically).

It seems a complete no-brainer to me that, when it's re-framed, just use the existing headers, cut 'em off a bit shorter, and you're good to go. The county and their permit gestapos don't see it that easy; they want beam calcs done. (huh? I don't see how this is hard) Maybe they said that 'cause I showed them a set of plans that spec'd a 4x8 header? I dunno. They just knee-jerked an answer.

I figure I could go in there and try bluff my way through it to convince them they don't need beam calcs. But, if I had just enough knowledge about header & wall construction, and a few construction terms (yes, I'm a layman; I'm hiring a pro) to convince them I am not trying to do something weird or dumb, that would help my story a lot. There's no need for their usual process of complete plans review, structural/building permit, and 6 weeks of waiting around--for nothing. This really is a no-brainer.

My question: what's the max span of a 4x8 header? I figure if I can quote a few numbers like max span, they'll rest a bit easier and let me pull my other permits & go.



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Old 05-28-2008, 08:52 PM   #2
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Headed spans depend on how they are designed & type of wood used. Example, if it has OSB in the center vs. regular 1/2" plywood vs. insulation board sheathing. I'm assuming when you say a "4x8" header you mean two 2" x 8"s together? Typically a doubled 2x8 header made with Douglas Fir or Southern Pine No. 2 with 1/2" plywood sheathing as the center core will span roughly up to 8'-11" for your situation. (single story home)
Talk to your local inspector & he should be willing to guide you in the right direction.


CarpenterJim is offline   Reply With Quote
Old 05-29-2008, 12:17 PM   #3
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Thanks, Carpenter Jim.

Follow-up here....I went & talked to the county today, and I think I explained things "the right way". Once I told them we're just shrinking the two openings, they easily agreed there are no structural concerns.
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