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Re: Slightly off-topic question

To: Shop-Talk list <shop-talk@autox.team.net>
Subject: Re: Slightly off-topic question
From: "Peter J. Thomas" <pjthomas@adelphia.net>
Date: Sun, 23 Jun 2002 14:18:11 -0400
Randall Young wrote:

>The ceiling joists in my attached garage (which I use as my shop) are 2x6
>beams on 4' centers (yes, 48" centers) that span roughly 24' between the
>walls.  Obviously the original intent was only to hold the walls together,
>but the previous owner laid some plywood down and my wife and I loaded the
>space up when we moved in.  By now I'm not sure what all's up there, but
>it's probably mostly books.  Last night I looked up and realized that one of
>the beams is broken !  It's cracked about 3/4 of the way through and has
>sagged until it appears the load is actually being carried by some 8'
>fluorescent lights !  (I wouldn't have believed you could bend a fluorescent
>tube that far without breaking it.)
>
>My thought is to jack the beam up until it's horizontal, then lay a 16' 2x6
>on each side (one resting on each wall) and run bolts through all three 2x6.
>(I'd have to seriously disassemble the house to get a new 24' beam in
>there.)  Any comments on the flaws in my plan, or a better way ?
>Suggestions on how big and how many bolts to use ?
>
>TIA
>Randall
>
>  
>
The cracked appears, from your post, to be 6 feet from the wall.  Two 16 
foot joists would not overlap the break so you face the same failure 
again. Each joist would end 8 feet from the wall.

I would really try to get a full length joist up there.  You should be 
able to bow a 24 foot joist enough to get it up there.  Lay the joist 
flat, not on edge, on one wall.  Have a big friend hang on the center of 
the beam while you raise the other end into place.  Once up there twist 
the joist to put it on edge.

Either method will not produce a stronger joist, so it would likely fail 
again, either exactly at the old break or at the bolt holes.  In fact, 
you will stiffen the joist concentrating more force at the break. 
 Consider adding new joists in between the current joists.  I would also 
consider adding some more joists to in between the current joists.  

If you must use 16 foot joists to sister the broken joist, consider also 
adding 8 foot fillers.  This will sandwich the break between two new 
pieces of wood.

Rather than bolt which would compromize the strength of the joists, I 
would use wood glue to laminate the sister joist in place.  Wood glue is 
stronger than wood and bolt holes would compromize the strength of the 
joist.



Peter Thomas

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