Toilet drain line through floor joists?

kirkhallJanuary 6, 2012

I am in the planning for a remodel (and will be talking with a plumber soon). But, I was hoping I could get one question answered (this should be easy):

What size 2by joist is needed if you need to run a toilet-size drain pipe through it in order to get it to a drop wall (from second story to crawl)?

The toilet would be the only fixture on the run through the joists in this fashion (other fixtures would join in a joist-space near the drop).

I know needing to do this will add cost--having to cut holes for the drain line adds labor. But, I am just wondering how big the joist needs to be. (I have at least 2x10s, not sure if they are 2x12s yet (haven't crawled up there and moved insulation out of the way).

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davidro1

know this: many people forget to mention (or to think of) using steel flat bars as joist reinforcement. It's like sistering, but using steel. It's not a big deal to drill holes in steel.

Web search for cutting holes in joists. Or wait for a specific answer in the next post by anyone else.

    Bookmark   January 6, 2012 at 8:58AM
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davidro1

forgot to mention: Remodeling experts know about joist strength and mechanical strength. The question is not a plumbing question, but some plumbers will know what the published guidelines are for cutting holes in joists.

http://ths.gardenweb.com/forums/remodel/

Here is a link that might be useful: remodeling forum

    Bookmark   January 6, 2012 at 9:14AM
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brickeyee

There are repair plates available for specific joist sizes for drain lines.

Anything much else can require an engineers stamp to satisfy the AHJ.

    Bookmark   January 6, 2012 at 9:55AM
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kirkhall

Okay. Not as simple as I thought. Thanks guys.

(The joists in my case do not exceed 9 feet, since I am sure that will matter.)

    Bookmark   January 6, 2012 at 11:44AM
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kirkhall

In case anyone finds my post later, I got an answer on the remodeling forum as suggested by davidro1:

The code says board/3 at minimum, as long as you are at least 2 inches away from each side. So, a 2x12 is the minimum.

Hope I have that.

    Bookmark   January 6, 2012 at 4:52PM
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brickeyee

You can also use smaller joists and then put an approved repair in them.

    Bookmark   January 6, 2012 at 5:20PM
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davidro1

after you measure the outside diameter of the pipe, and then add a fraction for the hole to be bigger and to allow the pipe slope too, you may be over the limit of a 12 inch joist.

So start thinking about metal. If you buy 1/8" flat bar the inspector will see it is overkill compared to any sheet metal "repair kit". Is there an inspector? If so, consult him.

    Bookmark   January 6, 2012 at 5:31PM
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brickeyee

Look around here.

Here is a link that might be useful: Joist repair

    Bookmark   January 6, 2012 at 5:31PM
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kirkhall

All great advice.
Yes, I will have a city inspector, but depending on which one I get, I will be more or less confident in their "inspection". (I have to be honest and say, with our addition, one of them was much more thorough than another--who didn't go into the crawlspace to inspect anything, for example).

As for where in the span, it could go anywhere along the length of it, I believe. So wherever is best, we can do.

    Bookmark   January 6, 2012 at 5:56PM
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