I’m taking down a wall between my livingroom and kitchen, the span is 7 1/2′, there is no load bearing walls above, but it does carry the floors. I’ve got 12′ spans on either side of the wall and the joists are 2×8’s(the house was built in 1952). I want to flush the cielings, so i’ll cut in the beam and use joist hangers. my question is, what do I need to handle the weight? I was thinking 3 2×8’s with 5ply 3/4″ plywood sandwiched between them with construction adhesive. Is that enough or overkill? Tim
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I don't think you'll find anybody here being real comfortable with telling you what to do in this case. "Load bearing" is a legal term used in building codes. Gravity doesn't care whether we call a wall load bearing or not. The weight of a non-bearing wall is not zero. I can guess that your beam might have to carry something like 2000 pounds per foot, but that would be just a guess. In that case, the beam would have a maximum bending moment of about 14,000 foot pounds, and you'd have to provide support for 7,500 pounds under each end going all the way down to the ground. If that guess is correct, then two 2x8's of #2 Doug fir would be enough. But if the real load is, say, 4000 pounds per foot, that would be insufficient. So, don't risk your house on somebody taking a guess sight unseen over the internet.
If there's a building department that issues permits and does inspections where you live, ask them what they require. Bootlegging structural stuff can give you loads of grief in the future when you sell the place, even if it's all solid as a rock.
-- J.S.
Saw your question earlier this morning and I didn't reply as I didn't know how to put it. John has said what I would have said but with the tech side I am not qualified to even speculate on.
Having said that, I did replace a beam in a house. The span was 20 feet. The homeowner and I went to home depot and inquired about glue lams etc... They have engineers who will calculate the size of beam required. We had to furnish pictures of the exsisting situation and the plans for the final "look". They then gave us the sizes of beams we required to do the job. Next visit was the town hall to get the permits. With the HD specs of the beam the town eng. aproved the plans.
All in all one days leg work saved a ton of problems later on.
Amazing how HD differs from place to place. Out here, the head of their lumber department saw me taking an hour picking thru 2x6's, and the conversation resulted in me explaining to him what that funny black printing on the wood was all about. The upside is that I get SelStr for the same price as #2.
-- J.S.
Use LVL's. Go to your lumber yard and get the pamphlet from the mfg. There are tables there for sizing your beam. But I would guess you have a 660# / lin. ft. load and a total load of around 5000 # (that's 15# dead load and 40# live load) . IF (and this is only uninformed speculation) this is true, you have a 2500# load at each end of the header, how are you dealing with that?
Are you sure there is no roof load on those joists? Unless you have a manufactured truss roof, or no interior walls you likely may have roof load on those joists.
If you are going to build a beam yourself, know, with some kind of assurance other than "this ought to be enough", that what you are doing is enough to carry the load, (all the way to the foundation).
thanks for all the info, I ended up using 2x8, 3/4 ply, 2x8, 3/4 ply, 2x8 glued and screwed, used pl poly cons. adhesive. the opening is 7'. Tim