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We have a living room floor with a span of 28 feet. The floor joists are 2X 10’s on 16″ centers with a laminated beam of 3- 2 x 12’s with 1/2″ plywood sandwiched between each 2 x 12 down the center. The floor is 3/4″ plywood that was put down with nails and construction adhesive. What can we do to take the bounce out of the floor.
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Jim,
At this stage of the game it could be a very big deal..
How bad do you want this?
Ed. Williams
*2X10s spanning 14 feet don't seem all that long. They shouldn't feel too bouncy, unless the beam is contributing to the "bounce". On your center beam - the 3 2X12s - How far apart are the posts ?Also - Are you sure the beam is in the b center of the floor ?
*I have a similiar floor on a job I did a few years ago. Except that the center beam is steel. I was advised by the engineer to sheath the floor bottom with 1/4" plywood or OSB. If I couldn't sheath the whole floor at least do large sections. The idea is to create a rigid box, thus improving the joists ability to work together. Haven't done it yet so don't know if he is really knowledgable or not.
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Jim is this floor over a crawl space or basement?
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Had a similar problem that was stiffened considerably by running solid bridging in the middle of the span. If You don't have access from below and the floor is carpetted You could pull back the carpet and get to it from above. Depends on how bad You wanna fix it.
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The floor is over a basement, so access is no problem.
*We would like to eliminate at least some of the bounce.
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Jim,
I'll assume that you are doing this yourself within a reasonable budget,and have access to the joists from below. I question whether the builder used douglas fir for joist material. The bounce is due to the stretching of the wood fibers.You may start w/"sister" joists [attatched to side of existing] at every third joist. Mechanicals and bridging will need to be dealt with. It is helpful to rip a small bevel on the top leading edge of the sister joist to allow it to tip or "roll" into place. Doing this under tile floors can cause damage. An option is to use 2x8,aligned w/bottom of existing. In either case the sister is glued and nailed. "Sisters" can be added to further stiffen as needed. At a minimum, 3/4" plwood may be glued and nailed both sides at the center point of joist. 1x2 strapping applied at 90 deg. to joist on bottom edge will help spread
the load a bit further. Food for thought, Rick
*Jim, I'll assume that you are doing this yourself within a reasonable budjet,and have access to the joists from below. I question whether the builder used douglas fir for joist material. The bounce is due to the stretching of the wood fibers.You may start w/"sister" joists [attatched to side of existing] at every third joist. Mechanicals and bridging will need to be dealt with. It is helpful to rip a small bevel on the top leading edge of the sister joist to allow it to tip or "roll" into place. Doing this under tile floors can cause damage. An option is to use 2x8,aligned w/bottom of existing. In either case the sister is glued and nailed. Additional sisters can be added to stiffen further. At a minimum, 3/4" plwood may be glued and nailed both sides at the center point of joist. 1x2 strapping applied at 90 deg. to joist on bottom edge will help spreadthe load a bit further. Food for thought, Rick
*Not to sound too obvious but if it's in a basement why don't you just put a post under the triple 2 x 12? The bounce is almost certainly originating there since a 14' span with 2x10 isn't too bad. If a post isn't possible, then possibly a steel beam directly underneath the triple, depending on headroom. These may not be the ideal solutions but are cheap and simple.
*Jim, In that case, if you can see the joist from below, it's going to be easier than I thought. I would go with the idea of solid bridge blocking first. Be sure your joints are tight. This should help. Bolting on sistered up 2x8s is also a good idea unless there is a lot of plumbing and electrical in the way.Ed. Williams
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Jim I think Nick is on the right track with the post. If the bounce is confined to the 14' joist span then you might simply strap the bottom of the joists at midspan with a 1x4 or metal strapping. This reduces the joists ability to deflect thus decreasing the bounce. You might stand in the basement while holding your hand against the triple 2x12 and have someone upstairs bounce the floor to help determine if the girder is part of the bounce. Hence the post. If you use solid bridging blocks you might want to use a little construction adhesive on the ends of the blocks to reduce the risk of future squeaks. I'm assuming the basement ceiling isn't finished with drywall?
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We have a living room floor with a span of 28 feet. The floor joists are 2X 10's on 16" centers with a laminated beam of 3- 2 x 12's with 1/2" plywood sandwiched between each 2 x 12 down the center. The floor is 3/4" plywood that was put down with nails and construction adhesive. What can we do to take the bounce out of the floor.
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Back again. In my floor the first try to stiffen the floor was to install more blocking. Not very successful. Since I already had a very rigid support structure at both ends of the floor joists additional posts were not called for. Sistering joists is both expensive and difficult to install on an after-the-fact basis if you want them to support the load at both ends.
Thus, the best, cheapest answer is making a stress-skin box by sheathing in the bottom of the joists. Since the skin is not handling large loads one can use as thin as 1/4" material. As I said before I haven't done this myself, but the engineer did point out places it has been done and the floors don't bounce.