Re: 20'+ 2x6 ?

Instead of searching for very long dimensional lumber, why not make some "engineered joists"?
Its common practice to use 2x3 or so for the top and bottom plate of the joist sandwiching 1/2" osb in an I-Beam configuration.
(End View)
XXXXX <---- 2x3 Top Plate X X <----- 1/2" OSB Sized to carry load needed. X X XXXXX <----- 2x3 Bottom Plate
Just dado the 2x3 to take the OSB. Makes for a very strong joist and inexpensive joist. If you are willing to build them. Or buy them for that matter.
All depends on what type of load is being carried above the ceiling.
Just one possibility
Rick

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On Sun, 17 Aug 2003 18:54:00 +0000, Scott Moore wrote:

DAGS on LVL (Laminated Veneer Lumber)
-Doug
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Surely they could order you one. Just out of curiousity, how are you going to put it in place.
On Sun, 17 Aug 2003 15:59:15 -0500, D K Woods

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A 21' 2x6" isn't going to hold much load without a fair amount of deflection, so it should be "hung" from the rafters by nailing a vertical 2x4 from joist to rafter. You also can use 2- 12' 2"x6"s butt jointed with another 2x6 nailed to overlap the joint to make the 21' joist. It is also easier to install. You can also add a "rat run" as we call it around here. Run a 2x4 or 6 horizontal across the joists at the center of the span. To the 2x4 nail a 2x6 or 2x8 vertically to the 2x4 to form a right angle. Now, by nailing the rafters to the rat run, you space them on the proper centers, you level the ceiling and you add more strength by tying the rafters together and the 2x6 or 2x8 acts somewhat as a support beam.
When I was building houses, I occasionally needed lumber to 26' or so. My lumber supplier had to order it and it took a few days, but it was available.
Preston

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Hi,
Have you looked into the feasibility of using "Micro-lam" beams for your application? Tom

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Butt up two and sister them with about a six footer on one side, with lots of nails, preferably ringed.
Drop a couple of vertical 2X4 from the rafters to really stiffen it. Wilson

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I sisterd my sagging rafters with the box beam approach. I had to span 20 feet and had a clearance of 10" from top plate to roofing. A heck of a lot of nails, but them things are dead flat and incredibly strong!
-Bruce
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20' are possible but you pay such a hi price. Try engineered lumber. TrussJoists (or equivalent) will be a good possibility. MicroLams are not as feasible for what you want, although an option.
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See http://www.awc.org/Publications/update/ASD-Manual-Errata-Apr_03Notice.pdf for one site that has joist span tables.
Spanning nearly 21' is asking too much of a 2x6, and you can't add any load, even a ceiling (assuming drywall). You probably should look into getting an LVL beam (the wood I-Joists required here are nearlt 12" deep also). You could get away with something 7-1/4" deep, if you're not planning on storage in addition to the ceiling. See http://www.wsitruss.com/ewp36.asp .
Also see http://www.apawood.org /
Renata
On Sun, 17 Aug 2003 21:04:45 GMT, charlie groh

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Sir, with all due respect, I would not span ANYTHING 20' long with a 2 x 6.
wrote:

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If all you want is a ceiling to satisfy some requirement, wouldn't it be easier to hang a grid from wires and put up a suspended ceiling?
Lee
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The inspectors around here would require "engineering" if you tried to hang anything from the "collar ties". These are structurally in tension and could be replaced with steel cable in the design. The purpose is to prevent the walls from bowing out when the lateral load of the rafters is presented. When you start adding members to carry vertical loads you are creating a truss. That requires load assessments (AKA engineering). Perhaps you should consult with the building department to see what they are going to expect. They may accept diagonal bracing with a bunch of nails or they may want to see how you determined what to use.
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I went down to building code today. I learned a lot, and between us we worked out a plan that they would accept. However, I have not filed it as yet.
What they proposed is to take #1 or better 2x6es on 16" centers, or #2 2x6, 12" centers. Looking through a book I have, that appears to be on the very edge of the span table for absolute no load attics. Also, it does nothing to correct the perceptable sag that exists in the collar ties that are there. I also discussed the midspan support ideas with them, such as tying to the rafers above (would bow the roof), and placing a beam traverse to the collar ties and effectively halving the span (needs engineering work).
Ive been thinking about it all day, and I am not happy with this solution. A neighbor with an identical house changed the 48" OC 2x6es to 24" OC 2x6es (by adding every other one), but also arranged a beam across the garage as well. I would really like to do this as well, and am thinking I might have to involve an engineer at this point. Its my house, I want it solid, I don't like the idea of being at the edge of what the code allows, and I would like to reduce the sag from front to back just as I wanted to reduce the sag between joists. With the beam, the 21' span is effectively halved, and that fits the span table well. Ideally, I would like to mount the new beam above the joists, the reason being the garage is to be a shop, and I like to have maximum clearance.
Whats the best way to get a plan together that building permits will sign off on ?
Thanks in advance.
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Scott, go back to the lumber yard and ask for 22' engineered beams, they are wafer board between two 2X2s can span up to 24 feet with no sag. They are light and easy to work with and very strong. Also meet codes. Cost about the same as regular 2bys. Muff
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Scott Moore wrote:

I think the more interesting question is: How to you plan to get the beam above the joists?
Of course, I haven't seen your garage...but every garage I've had would be a realy challenge!
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he just lives in an upsidedown world ;-)
Renata
On Wed, 20 Aug 2003 12:49:06 GMT, Chris Merrill

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Chris Merrill wrote:

I've done it by passing individual pieces into the area through a gable end vent and then assembled them in place. Actually worked quite well.
Scott
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