4X8 beam question


Old 04-13-04, 08:10 AM
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4X8 beam question

Because of clearance considerations, we are going to have to use double 2X8's for beams rather than the prefered double 2X10's The joists will be 2X8, 16"O.C. There will be two beams, six feet apart - for a joist span of only six feet. However, I would like to space the support posts seven feet apart, with the ends of the beams overhanging the end posts one foot. I have never done anything using 2X8's for beams. will this post spacing give a solid feel?
Old 04-13-04, 07:25 PM
Join Date: Sep 2003
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Lots of detail, but no context.

Allow me to guess the context.

You have removed at least one "load-bearing" partition wall. There are people in your life avoiding you. The laundromat has posted signs saying "remove all plaster dust from pockets before washing".

You want to install a header under the ceiling . A 2x10 header will eat up too much headroom. You think a 2x8 is the most wood you will tolerate.

What is above? Attic and/or living space? If you have attic space, and the roofing load isn't transmitted to the partition, then all you are 'loading' is the ceiling and it's joists. Your chosen path would reveal itself to be less burdensome.

If you have manufactured trusses above, you probably have zero loading. Somebody wanted a wall there, but it wasn't holding anything up.

So, what are the loads?

You could have:
Roof load
One story of living space (how wide, I don't know)
Two stories of living space (again, I have no idea how wide the rooms are)
Attic/ceiling load

In some combination.

HomerTheFoamer responded to a similiar situation with an excellent response. I am following in his footsteps with my reply to you.

I continue guessing...

Your header doesn't need to be under the wall. You need to 'bite the bullet' and strip off the ceiling on each side of the area in question. If you are lucky there are no pipes or heat ducts in the way. Electrical is easy enough to detour since it ignores gravity.

You would then use a SawzAll to trim the ends of all intersecting joists to allow insertion of your header. Perhaps it will be two pieces (3 inches) thick or 3 pieces (4 1/2 inches) thick, or perhaps 4 pieces (6 inches) thick. Depending on your joists, you will be many inches ahead of the game by this tactic. Each joist will be in a joist hanger attached to the header.

There is no shame in approaching a structural engineer and asking him to calculate loads. A good builder could do it also. I prefer engineers because they are up to their butts in college loans and won't make fun of you (they need the money).

You may end up with a header protruding downwards, but you will know you did your best to avoid it.

And of course, if you have a wall directly above that could be converted to a stressed-skin panel, you wouldn't need a header at all (you would need an engineer at this point). Columns perhaps, but no header.
Old 04-14-04, 05:28 AM
Join Date: Mar 2000
Location: Arlington, WA
Posts: 9,238
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Are you building a wall? A deck?

Is this a header? A ledger? A rim joist?

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