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Old 03-02-2009, 04:03 PM   #1
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Shower drain is directly over a floor joist

I have to install a new shower replacing an existing one. The drain from the shower I want will be directly over a floor joist, so I'll need to cut a 6" section or so out of the joist to make room for the drain. What are the options for doing this?

I'm thinking of placing a second joist next to the existing one (with a spacer), joining them with lag bolts, and then cutting out the section I need. Will this work?


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Old 03-02-2009, 04:42 PM   #2
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could you post a pic of the bottom of the joist so we can see what your upagainst. and let us know what the span on the joist is wall to wall. BOB


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Old 03-03-2009, 08:01 AM   #3
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If access to the floor system is available (unfinished basement), it is commonplace to either sister a new joist to the cut one as you mentioned, or to cut the joist off and header it at either side of the shower drain. The header option is a good one if done correctly and if there aren't unusually high loads on that part of the floor (bearing walls, etc).
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Old 03-03-2009, 11:09 AM   #4
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The attachment shows a sketch of the floor joists around where the shower is to be placed.

The joist I need to cut is 12" from an interior wall. The joist on the other side is a tail joist of span 80" between the stairwell header and the outside wall of the building. I understand that if I cut a joist within 4 feet of the main support, it can be supported from the adjacent joists without having to add additional support to those joists. This makes sense to me because that close to the supports the joists are mainly in shear load and do not have a significant bending load. In this case the span of the joist is only 80" so its loading will be very light.

So I guess the correct solution, distilling replies so far and other posts to this site, is to:

i) Cut a 18" span out of the joist in question.
ii) Add a header to the cut ends and support from the adjacent wall and the adjacent joist.
iii) Additional support of the adjacent joist is not required.
iv) Water feed lines will have to be cut to allow installing the headers.
v) The headers will have to be drilled to allow reconnecting the water feed lines.
vi) The south end header will have to be drilled to allow passing the show drain line.

Thanks for your responses so far. Things are not so sad after all.
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File Type: pdf ShowerDrain.pdf (35.1 KB, 834 views)
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Old 03-03-2009, 04:56 PM   #5
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Quick fix with plenty of room

<P>SAD, since 2by 10's n 12's carry agreat load. you shouldn't have a problem just measuring back from yor header and creating another box jost like the one for your stairway opening. Cut your joist down to size including the 3 inch for your header. (When removing joist pieces, watch out for the sub-flooring nails and the (GLUE) if the house is new enough to have been built with it.) Nail on first headerboard than the next, than add hangers to joist. Last nail 2 hangers to hold up header board.
I've attacched a quick sketch 4 you, but I'm new here and not sure how to load it up?
Not to mention this is a new pc and scanner so I'm getting used to everything!
Hope that I can help you!
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Shower drain is directly over a floor joist-scan.jpg  
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