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Posted by Joe on November 3, 2007, 9:37 am
> > hoping someone can answer this.
> >
> > i have a few 2x10 joists that have horizontal cracks.
> >
> > each joist has only one crack.
> >
> > they all appear to originate from where the nails
> > went in to secure the joist to the joist hanger.
> >
> > these joists also have bridging in the center span.
> >
> > my question is, if these cracks are stable over
> > years and have not grown in length. is it safe to
> > presume they were from the original construction,
> > and not from being stressed ? (ie. heavy loads on
> > top).
> >
> > the other question is, if the crack originates
> > from the end, where it's resting on the hanger,
> > wouldn't a load on top, tend to compress the crack
> > together ? (since the hanger is providing some
> > resistance from the bottom of the joist).
> >
> > and thirdly, what does "sistering" the joist
> > actually do ? it would seem to be futile, since
> > the sistered joist, would need to be in a hanger
> > too to support the weight wouldn't it ? (i don't
> > see how just lag bolting another 2x8, 2x10 next
> > to an existing joist is going to help that joist
> > bear any loads that are vertical - since the
> > sister joist isn't resting on anything - just
> > lag bolts - and the forces are still transmitted
> > to the existing joist hanger of the existing
> > joist).
> >
> > thanks in advance for any responses.
> >
> > basically i'm wondering if i should worry about
> > those cracks or not - they are stable, and have
> > not changed in size. the joists in question are
> > also sorrounded by doubled up 2x10 joists, 16" away.
>
> Well Joe, I think you worry too much. It is very common to run into
> 2x10's and 12's with splits on the ends, especially douglas fir
> joists. Not that I like it, but you just have to use them and it has
> always turned out fine. There are probably several reason the crack
> doesn't compress together. First, there isn't THAT much weight on any
> given joist. Second, the joist usually doesn't wind up resting on the
> bottom of the joist hangar--it shrinks up off of the joist hangar and
> is actually held by the joist hangar nails working in shear.
> Sistering can make sense if you are looking for a stiffer floor, for
> example. I'd guess it is best to have the sister supported on its own
> (by a ledger or maybe a new double hangar that goes over both joists)
> However, it may be that the joist hangar on the orginal joist has
> plenty of capacity.
>
> Are your floors real bouncy? If they are, there is a small chance the
> splits are something to be concerned about. But if you have no other
> indications that your floors are underframed, I wouldn't worry about
> it.
thank you for the replying.
yes, they *are* douglas fir joists.
no , there is absolutely no bounciness at all. the floor is rock
solid.
i guess i won't worry about it, but i marked the end of the crack
with a pen, just in case (to monitor if it grows). it's been stable
for years, so i think you're right. it's probably nothing to
worry about.
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