cutting joist to install toilet flange

[skeezix]

You guys are awesome... maybe I can run something past you. This may or may not be a plumbing question... but here goes.

We are looking to move a toilet in a 1924 second floor 5x9 bathroom. I believe that the toilet will need to be install directly above an existing joist. I have read that you can cut the joist and build a header box around the closet flange. I will also have to bore sideway through two other joists to connect to the main drain/vent stack. One of ends of the joist (near window and toilet) is a exterior wall and the other end has a load bearing wall sitting on it. Question, if you only cut one joist in the system, do you generally need to brace it first? Or can you temporarily get away with not bracing as long as you install the headers right away?

Thanks,
Scott

[LazyPup]

In general I would never, under any circumstances cut a joist unless there was adequate provision to support the remaining portion of the joist during the change out.

Having said that, it would be almost impossible to give you a definite answer to your question without actually seeing the situation and having a copy of the local codes specific to your locality.

Both the International Residential Code and the Uniform Plumbing Code have tables that define the rules of notching and boring based upon the thickness of the joist, length of the span, the rated "Live load" on the floor and the physical position where the notch or hole is required, however your local codes may use different tables.

While you are correct that a header box can be created to meet your needs, I would not venture to do so without first consulting with a bona fide framer or structural engineer familiar with the specific codes in your area.

[ABP]

If I may, I am a building contractor and it is NEVER safe to cut out a joist. First off the header would need to be doubled up, and the "Carrying Members" (the joists on either side) would also need to be doubled. The joists to the side need to be doubled because they have to now carry 50% of the load that the one you cut was carrying. This would be better fit for a framer or carpenter (And a reputable one at that) Also I agree with LazyPup, the plumbing code says you can not remove more than 1/3 of the material. So if you have a 4" sewer line and you need to go through the other 2 joists, they will need to be 2x12 (12" divided by 3 = 4") As a builder I agree with Lazypup and would realy seek advice from a reputable carpenter as I have seen the damage done by this. And PLEASE check the reputation of the person to do the work, such as licenses and referals.

[skeezix]

Thanks... that is what I was thinking. I found a lot posts about cutting the joist and making a header box... and they all made it sound like it was a really simple and low impact process... which I found odd. You're cutting a structural component of the house, for crying out loud! I will try and find a good framer, and if I can't... I will way over-do it on the braceing. Better safe then sorry.

I already understand the boring/notching codes for my area, and I also understand the comment on sistering the joists and doubleing the header. If I end up doing this myself, I will make sure and do it right.

[ABP]

I tell you what, if you can not get a pro to do it, contact me and maybe with some pics I can help with your project. There may be other alternitives to sistering joists. I would need to see some pics of the work area. Say from the floor under the toilet (With joists exposed) and a picture of the floor below that one too. I may be able to suggest other means of support that will pass code. Also, where is the work going on? (State, county, Country)