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Old 09-30-2010, 07:36 PM   #1
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Floor joist weight capacity?


Hi,
I just gutted my 2nd floor master bathroom (144" X 91") and I found that my floor joist are not true 2 x 8's but they are 2 X 7(exactly). In fact one has been severly notched about 5 inches worth to allow for plumbing. My question is I want to move my toliet 3 feet which means going through 3 floor joist. I also want to add a 66" tub, a double vanity and enlarge the shower to 5 X 3 ft. I want to know if my floor joist will support all this new weight while comprimising 3 joist for the toliet relocation. In addition I will be drilling through 3 other floor joist to add the tub and double vanity drains, which are all going in the floor. Even if I was to sister up or add a few joist would the floor be able to handle this new load? ( main concern drilling a 3 1/8 hole through my 2 x (exactly 7) floor joist)

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Old 09-30-2010, 08:08 PM   #2
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Floor joist weight capacity?


What you propose to do would be a serious comprimise to the structual component of your flooring system. I would not do this would consulting a professional in structrul wood frame.

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Old 09-30-2010, 09:50 PM   #3
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Floor joist weight capacity?


Could you run your new plumbing through soffits below your floor joists? I would not do what you are proposing plus I would be looking to strengthen the one damaged by the notch.
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Old 10-02-2010, 01:46 AM   #4
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Floor joist weight capacity?


I'd rethink this, myself. If the 2x7s have been working, the all is well for what they have done. But, when you start nuking them and adding weight, you better have a good idea of how much weight and what your spans are. Cutting out 3 floor joists: Will these then be tied via a "header" into neighboring ones, who will then take their load? Yikes! The neighbors need some beefing up, if not all of the floor joists. Go higher as opposed to doubling, if you have the room.
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Old 10-04-2010, 10:12 AM   #5
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Floor joist weight capacity?


Thank you for your replys, One question to Jkingel, you mention " go higher as opposed to doubling" I assume you mean add a 2 x 10 instead of double my 2 X 7's... The only way I can add joist is to do it in 2 pieces( due to the load bearing wall being 48" beyond the wall I gutted) So I found a person that can make a custom metal plate that will allow me to bolt two pieces of 2X7 together to form 1 complete floor joist. I also found a web site that sells metal joist renforcers to help with bored out beams. I will try to add as many new joist as I can. And I will not move the toliet as first purposed, but relocate the shower to a hall closet that I must now remove as well.
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Old 10-04-2010, 12:29 PM   #6
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Floor joist weight capacity?


Quote:
Originally Posted by toph236 View Post
Thank you for your replys, One question to Jkingel, you mention " go higher as opposed to doubling" I assume you mean add a 2 x 10 instead of double my 2 X 7's... The only way I can add joist is to do it in 2 pieces( due to the load bearing wall being 48" beyond the wall I gutted) So I found a person that can make a custom metal plate that will allow me to bolt two pieces of 2X7 together to form 1 complete floor joist.
Yes; higher is better. Uniform load strength is a function of the square of the height; double the height, quad the load. Instead of a custom metal plate, can you sandwich the two 2x7s between two pieces of 3/4" plywood, then glue/screw/tattoo them together? Make the plywood as high and long as you can. I JUST HAD A THOUGHT for Dan or one of the other engineers here: see "Making a joist a T" thread I'm going to start.
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Old 10-04-2010, 12:38 PM   #7
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Floor joist weight capacity?


If you are in a jusridiction that requires permits for any of the work you are doing I would get legal and take advantage of the inspectors input before doing additional work. If you are going to significantly change the load or cut into framing materials (joists for example) there's a decent chance your inspector, if any, will require an engineer to bless the project and even if not, that's money well spent for this job, IMO.
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Old 10-04-2010, 04:10 PM   #8
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Floor joist weight capacity?


If you get a permit, make sure you have a copy of the construction/inspection approval from the city for use when you or your heirs decide to sell.

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