How to install a flush laminate beam?

weedyacresMay 17, 2008

We're rearranging our upstairs walls a bit to add a bathroom between two bedrooms. Here are the prints. Note the dotted line, which is the current load-bearing wall.


The prints call for it to be replaced with a flush laminated beam, which, if I understand correctly, means putting a beam above the ceiling, suspended from the joists on either end, and then hanging the floor joists of the room above to that beam.

We're DIY-ing this, so want to make sure that we're executing it correctly. We've pulled the drywall off the LB wall, and it's just 2x4s. Up in the attic, the joists are 2x6s spanning the "new bedroom" and 2x8s spanning "bedroom #3", and they intersect and rest on the 2x4 LB wall. Here's a photo showing the intersection above the LB wall. The board in the lower right is just the frame for the attic access panel.


And here's a couple shots of the attic. We want to eventually finish it into a 20x20 room, which will require beefing up the floor joists to 2x12s.



So back to the laminate beam. Our thought on how to install it is to build the 2 outside bathroom walls to provide temporary support for the joists. Then climb up in the attic, cut the joists off so that a beam can fit between them, hang the beam to the joists on the outside wall and the inside wall, then hang the just-cut joists to the just-installed beam.

Are we in the neighborhood here, or completely off-base?

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sombreuil_mongrel

Is the new beam sized properly for it's future use- carrying the new 2x12's for living space, or just sized to carry ceiling joists for an attic? No point in doing the latter if it has to be re-engineered down the road.
I would do the work from below, not above. I'd get some temporary walls in first,about four feet apart; cut out 3 feet of ceiling, and fit the new girder from below. IMO it's much easier to lift it in than to deal with moving wires so it can drop in.
Allow an extra quarter inch when trimming the ceiling joists. Put a nail in every hole of each joist hanger. It's easy.
The point loads at either end of the girder must bear through to foundation. Look at what you have at the stair well- a rim joist is okay, too, but not a double plate by itelf.
Casey

    Bookmark   May 18, 2008 at 10:25PM
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theporchguy

Need more information. The Porch Guy

    Bookmark   May 18, 2008 at 10:31PM
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weedyacres

The beam should be sized for a live load in the attic (they did plans for the bath as well as new stairs/attic), but I'll double check. I never thought about installing from below. That helps with the "how the heck do we get a 25-foot beam up into the attic through an itty bitty hole" question.

I'll go up in the attic again and see what's at the stairwell.

porch guy: what other info do you need?

    Bookmark   May 19, 2008 at 8:10AM
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bill_g_web

Fine Homebuilding number 152, January, 2003, page 80, has an article, "Removing a Bearing Wall", in which they install a beam in the ceiling, just as you want to do. Go to finehomebuilding.com, seach for "Removing a Bearing Wall" to locate the article, but to view it you need to become a member, though they offer a free trial.

Bill

    Bookmark   May 20, 2008 at 11:21AM
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manhattan42

What you propose cannot be done.

1st, the lam beam cannot be 'suspended from the joists on either end'. Beams and girders must be be supported on each end by structural columns which transfer their weight directly to the foundations and footings.

2nd, a lam beam needs to be engineered (by an engineer) to carry all loads placed upon it.

3rd, the size of the ceiling joists for the approximately 18ft + spans must be at least (generally speaking) 2x10s or deeper at 16" on center to carry the ceiling loads.

-----------------------

The bottom line is that no one here can help you and you will need to engage the services of an engineer or other design professional help you.

    Bookmark   May 20, 2008 at 7:31PM
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weedyacres

We did hire a design pro who drew the plans and consulted an engineer. My DH called them back and they confirmed that the beam is sized to support the live load in the future finished attic. And we can make it just 13' long (the length of the wall we're removing), and use headers across the last 7 feet or so (2 doorways).

On more crawling around in said attic, I realize that I misspoke on how said beam will be supported. It will rest on the outside wall of the house and an interior load bearing wall. We'll then hang the joists from the beam.

So we're off to buy a lam beam and get to work. Thanks a million bill v for the article (duly joined/saved/soaked up like a sponge) and sombreuil for your tips on doing it from below.

    Bookmark   May 21, 2008 at 10:27PM
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weedyacres

I'm happy to report that we've got our beam in! DH and DSS did it with a lot of sweat.
1. After putting up temporary support walls, DH cut the LB wall out as well as the two joists, creating the gap for the beam.

2. DSS handed him up the beam in 2 parts, he bolted it together with lag bolts every 2 feet, and set it in place on the rim joist and another LB wall 20 feet away.

3. DH attached all 43 joists to the lam beam with joist hangers while DSS watched and they bonded.

Anything that looks wrong before we remove the supporting walls and button up the ceiling drywall again?

    Bookmark   July 12, 2008 at 8:20PM
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sombreuil_mongrel

Good job. Looks fine. Hot in that attic, eh?
Casey

    Bookmark   July 13, 2008 at 12:39PM
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weedyacres

Whooeeee, hot doesn't begin to describe it. DH was wringing sweat out of his jeans by the end.

While the ceiling was opened up, we fed up a bunch of polyiso insulating panels that we're going to attach to the rafters. Eventually (next year?) we're going to finish the attic space.

    Bookmark   July 14, 2008 at 10:21PM
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