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I have 2x12 floor joists under a second floor bathroom. They are 16" OC and span only 8'0". I would like to replace 1 of these with a double 2x6 to make some plumbing easier.

Is there any problem with this?
 

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Civil Engineer
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A nominal 2x12 with true dimensions of 1.5" x 11.25" has a moment of inertia of 178 in^4. A pair of nominal 2x6 with true dimensions 1.5" x 5.25" has a moment of inertia of 36 in^4. This makes the 2x12 about five times as strong in bending as the pair of 2x6's. Whether this is a problem in your particular case depends on the loads, the span, and the connection geometry.
 

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Framing Contractor
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i also see it as a problem , the 2x12 was put there for a reason
Not necessarily. When a floor is figured, it is figured for the longest span. All the joists generally are the same width, so this results in some joists that are way oversized. I would say to check and make sure that the span is indeed 8'. Just because a joist runs over a wall, doesn't mean that wall is a bearing wall.
 

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timthetoolman
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oh ohhh! Does someone need a soffit somewhere? Run it under the joists with a soffit.?. If you make it a little wider than the tub, this usually looks really good below. I like the sounds of 2X12 joists only spanning 8 feet, overbuilt how I like em. But don't mess with cutting apart your joists man...never a good idea.
 

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Its pretty unlikely theres bearing walls only 8 ft apart. You can drill holes in joist you know. How big of holes do you need? People always want to move structural elements to make plumbing easier, even on the contracting side of building. Theres a reason we frame them before the plumbing is ran. Be carefull when messing with structural elements.
 
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