Randall..
I'm suprised that only one joist has cracked unless you were joking to some
extent about "mostly books" up there. You are right that 2x6's at 48"OC were
not intended to hold any live loads, only the lateral loads to keep the walls
up.
Sistering the broken beam as you propose should work fine. I would use both
glue and some 5/16" lag screws with some hefty washers staggered at 12" OC. I
wouldn't rely on glue alone because it can be difficult to get joists to sister
properly under these condidions without mechanical aids.
I would find some way to get some additional joists in at 24" OC. if possible,
even if you need to nail a 2x4 plate on the face of the wall to help with end
bearing for slightly shorter joists. You could also build up the bearing plate
to the top of the existing 2x6 joists and use metal joist hangers. With the 48"
space you should be able to get a full length joist in diagonally.
The other thing that I would do is add solid cross bracing (2x6 perpendicular to
joists) between all of the joists at the center (or even better at 1/3 points)
to prevent twisting of the lower edge of the joists. When a 2x joist is
allowed to twist it quickly looses its strength and will fail. A simpler way
of blocking the joists is to just add a 2x4 the entire length of the room and
nail to to the bottom of all of the joists if you don't mind a bump in the
ceiling.
You have been lucky so far, hope it continues with the project.
Bill Hook
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
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