Building beam in attic to supportceiling
mnhunter2
| Posted in Construction Techniques on
I am remodeling a home built in 1960 and would like to get rid of a wall in the middle of the house that supports the 2×6 ceiling joist that are spliced above it. The house has a simple 2×6 rafter that is supported at the walls with 2×6 ceiling joist and no suport webbing in the attic. Next to the bearing wall there is a beam in the attic with the ceiling joist butted up to a double 2×12 and then used to upport the ceiling for 12′. What I would like to do is build another beam in the attic that would span around 20′, it would just have to support the ceiling weight. Can I build another beam next to the 12′ one that is there and how would I build it?
Replies
There is no way I would answer this question, let alone try to build what you are trying to do, without the assistance of a structural engineer.
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
Boris is right but you need an engineer to specify things or a framing contactor with the patience of a remodelor and the engineering training to select the beam. You must maintain load paths to foundation with the supports at the ends of the beam.
You might do it with two or three 2x12s sistered and using the proper Simpson hardware to join the joists to it and a good fastener and gl;ue sequence spelled out.
But the reason nobody will be specific here on this is that there are way too many variables that cannot be seen through the web connection and structural things like this can become liabilities.
However, there was an article last year in FHB about doing something similar for your general edification on the overal subject.
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You said you have a bearing wall with overlapped 2x6's resting on it. In the attic above this bearing wall is a beam. Next to this bearing wall is a double 2x12 with cieling joists butting it?????????????????????????
You want to put another beam in the attic and hang the ceiling joists from it. With cables maybe??????????????????
You have a beam spanning 12' and you want to double it up with one spanning 20'??????????????
I'm confused.
SamT
With the risk of being redundant, you should consult an engineer.
Assuming your loads are normal, you can probably get away with slipping some LVL's on top and using straps to hold the joists.
What is your exterior finish? Would it be difficult to cut a 3x24" notch in the gable end to slip a large beam in?
Jon Blakemore
Where are you located? In most jurisdictions, this would require a permit, and to get a permit you'd need an engineer's wet stamp on the calcs, even if you could figure them out yourself.
-- J.S.
Many years ago we worked in a house that had a beam in the attic to replace a bearing wall. It was built in place with 2-2x6's on the top and bottom, connected with 37 inch stiffeners and sheathed on both sides with two layers of 1/2" plywood. The ceiling beams were hung from this beam. It seemed to work perfectly and only one bay of drywall was needed to be cut out to get the materials into the attic. Now I'm sure that they would use lvl's. If you can calculate the load, the manufactures provide tables for the span and loads. If you can't calculate the load and figure how to support the ends, get an engineer to tell you what to do.
Good answer and would add one item from experience. Designed a built up 32 ft beam for brother's house to support second floor - recall it took about 3 hours to design, did it while waiting for court during jury recesses (on the jury) . 4 flat 2x6s on top and bottom glued and screwed together and to both sides of 3/4 ply web.
After he got it built (its been in place 18 years, no sag, etc, good shape) for about $60 worth of lumber and glue, he said it took he and an employe a whole day to build in place, he opines that doing it again he'd spring the $$ extra for a glulam and save the labor. Biggest advantage to the built up was it was part of an outside wall so the outlets, etc could be prebuilt into it that you cannot do with a gluelam.
In your case you could go with a gluelam and cut a hole in one end wall to get it in.
A built up LVL beam would be easiest to place, but my fist thought would be a zero camber, structural grade glulam, with Simpson hangers supporting the ceiling joists where they run under the newly placed beam. Piece of cake to design, not necessarilly so easy to install.
If all it's carrying is a ceiling (did you say how wide this ceiling is?) a 3+1/8 x 12 will probably be fine spanning 20 feet, but even a 5+1/8x12 is cheaper than the comparable strength combinations of LVLs.
If the earlier mentioned talk about load paths confuses you, stop thinking about doing this yourself and hire at least a professional builder. This is straight forward, run of the mill, remodelling, but nothing to be taken lightly.
Oh yeah, before you go removing bearing walls, you might consider what else that wall is doing for the integrity of the building, like shear values that wall might add to exterior walls it intersects with? There might be more to it than simply taking the weight of the ceiling. Think about the bracing value of any one wall as it forms a right angle with another...there is often more than meets the eye.
If I read this right, there's a 12' space that is already open, then 20' of midspan wall that you want to remove.
If this were new construction, that would be simple, you'd get a beam designed to span the 32' distance, and support it correctly. The ceiling joists would sit in hangers, and there's be a nice, flush ceiling when you were done.
As a remodel, it's just abit more messy is all. You can't just knock down the wall first & look at the work--you have to build some sort of temporary carrying wall, on both sides. Now, since you are tearing into the ceiling where the wall already is, the "mess" factor is already there.
Suspending the joists from the beam will have a host of problems in actual application, mostly in how to get a reliable, uniform, connection between the joists & the beam. You will likely have to create bearing for the beam, too, this may entail tearing into walls you hadn't planned on.
It's not impossible. The engineering is relatively straightforward (hopefully). However, the best (and "right" way IMHO) is to go up from below. Fit the beam, and then the joist hangers, then the joists. That way, everything can be trued up, and fastened to spec and in a workmanlike manner. Ok, that "job site" is a bit more scary, likely, than you were thinking. Probably 4' on either side of the beam, and the whole 30-something foot run. And not for a short stretch, either (count on it taking twice as long as it should). Afterwards, though, you get the space, and structural confidence that you deserve.
Oh, and I presume that a very pretty gluelam under the existing ceiling is a "no go" (1960 generally equaling an 8' ceiling, not the best place for 12" or so of gluelam to hangdown into . . . )
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One more thing to add. If you decide to add the beam in the same plane as the joists, with the joists bearing on hangers, you should consider how the lateral thrust of the roof will be handled. More than likely your 2x6 joists are acting as a tie to hold the walls together, and if you cut the joists and drop in to hangers you might interrupt this connection.
Jon Blakemore
Everyone's right so far as involving a structural engineer but to put you on the right track. I had a similar situation but with very little room to work in the attic. What the engr and I came up with was a box beam constructed from 2x frame covered with 1/2" struct I ply screwed to the 2x frame. I built the 2x frame approx where it was going on its side screwed the ply to the top side and rolled it over and screwed ply to the other side.
After the beam was constructed, I rolled up vertically supported the ends and middle with diagonal bracing down to the ceiling joists and used Simpson ties to attach the ceiling joists to the bottom of the beam.
Both ends of the box beam were supported by new posts let into the end walls.
Hope this gives you some direction
Bing
Remember that on a 20 foot span you need at least 20 inch of beam in width
If you have that ..no inspector can fail you