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Thread: Extend floor joists?

  1. #1
    DIY Junior Member mikeangelini's Avatar
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    Default Extend floor joists?

    Hello,

    There is a wall that extends out in our eat-in kitchen that I am looking to eliminate.

    In order to add the header that would make the ceiling flush from front to back, I would be cutting the floor/ceiling joists and pocketing in a 3.5" x 9.5" header in the ceiling using joist hangers. The span would be ~ 4 feet. I have done this in the past to achieve a smooth ceiling front to back.

    The problem is, the joists on the back side of the house are ~6 inches too short.

    The joists are 16" on center 2 x 10.

    The area above these floor joists doesn't seem to be carrying a lot of weight. Mostly just upstairs floor. No tubs, walls, etc. The area that would require the extending is approx 3 feet. Only 3 joists. If I needed to add 2 or 3 feet on, I would never think to do this, but since I only need 6" total added length, I wanted to ask opinions.

    In order to properly extend these joists to the header, can I scab two 2 x 10's overlapping ~4 feet on both sides of each joist, through bolt, and use construction adhesive to reach the hangers? I was thinking of buying the triple hangers. 4.5 inch wide to accept triple joist. I put a picture of one below.

    I would fill in the gap in between the 2 boards on each side with a 6" scrap so that a solid, triple joist goes into each hanger.

    I could pull down all 11.5 feet of the ceiling and set a new joist on top of the wall, but this would add a ton of work with soffits, bridging and plumbing, etc.

    I was also considering adding in bridging in between the extended joists, out onto the un-cut, longer joists on either side for more strength.

    In the pic, it you look closely at the top, you can see the overlapped joists and the wall. I want to make that over lapped joist reach the wall.

    Any help and advice is very appreciated.

    Thanks,

    Mike


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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by mikeangelini View Post
    In order to properly extend these joists to the header, can I scab two 2 x 10's overlapping ~4 feet on both sides of each joist, through bolt, and use construction adhesive to reach the hangers?

    I would fill in the gap in between the 2 boards on each side with a 6" scrap so that a solid, triple joist goes into each hanger.
    I would likely use 4' lengths of 3/4" plywood on each side of that block (that could also be made of plywood cut from the same sheet), then use 3" hangers. If what you have in mind is going to work at all, that will be quite sufficient where double 2x10s would be grossly over-doing it.

    Edit: I got to thinking a bit, and maybe some nice 4' pieces of 1x10 would be better than 3/4" plywood with internal voids. Also, and to make a bit of preload to be sure you do not end up with a sag, I would definitely jack those three joists up just a bit before extending them and removing their existing support.
    Last edited by leejosepho; 07-19-2013 at 03:27 PM.
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  3. #3
    Moderator & Master Plumber hj's Avatar
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    If the joists are too short, what are they resting on?
    Licensed residential and commercial plumber

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    DIY Junior Member mikeangelini's Avatar
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    They are resting on the header. I am trying to get rid of the little bump out that supports the header, and make everything flush with the wall. But 3 joists don't reach the wall. Hence my current issue.
    Last edited by mikeangelini; 07-19-2013 at 08:46 PM. Reason: Typo

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Don't they "overlap" the ones from the other side? That "header" if that is what you show in the second picture was not "professionally" installed, because no competent framer would just "slide" the header through that opening without making a "tight" fit around it.
    Licensed residential and commercial plumber

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    DIY Junior Member mikeangelini's Avatar
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    I agree. The more I see inside this house, the more I wonder how it still stands. The joists overlap where the big ugly header in the picture is. I want to move it back to be flush with the wall. About 14 inches. The joists don't overlap that far. I am moving it toward the front of the house. So the front joists are plenty long. I will make that side shorter, and the back side needs to be longer.

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    Moderator & Master Plumber hj's Avatar
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    IF they overlap, you should be able to bolt them together at that point.
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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by hj View Post
    IF they overlap, you should be able to bolt them together at that point.
    Sure, but first treat that like a cantilever situation and add some filler blocks so you can plate the sides with plywood. No inspector would ever let you just bolt joists together out past a load-bearing wall.
    "Great minds discuss ideas, average minds discuss events and small minds discuss people." --Eleanor Roosevelt

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    DIY Junior Member mikeangelini's Avatar
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    Thanks for the input so far.

    Leejosepho, I am trying to picture how you mean cantilever situation.

    I took a couple more pics to better illustrate the situation.

    They show the short joists, and also what they are supporting.

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by mikeangelini View Post
    Leejosepho, I am trying to picture how you mean cantilever situation.
    Using that term a bit loosely, that is what you would have if you bolted the short joists to the longer ones and then removed the support under the short ones. The short ones would then be a "cantilevered" load beyond the support under the longer joists. So, and where I would use glue and screws, add a couple of feet to all six joists, then plate the three overlaps with 1/2" plywood on both sides for a total thickness of four inches. By doing that you have sent the short joists' load over to the bearing wall without risking the compromise (possible breaking) of the ends of the longer joists...or something like that!
    Last edited by leejosepho; 07-22-2013 at 12:51 PM.
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    DIY Junior Member mikeangelini's Avatar
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    I see what you are saying.

    This would work if I was going to put a traditional header under the joists like what is there now.

    I was probably not very clear originally, but what I would like to do is have the ceiling be flush from the front of the house to the back.

    Put in temp support front and back, and then cut a 3.5 inch groove out of the ceiling joists to receive a header inside the ceiling that I would then joist hanger both sides to.

    The front side would just get cut shorter, and the back ones would get extended once the header is in the ceiling, nice and tight to the header.

    Does this make sense?

  12. #12
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by mikeangelini View Post
    I was probably not very clear originally, but what I would like to do is have the ceiling be flush from the front of the house to the back.
    Only for the width of that area under three joists?

    Put in temp support front and back, and then cut a 3.5 inch groove out of the ceiling joists to receive a header inside the ceiling that I would then joist hanger both sides to.

    The front side would just get cut shorter, and the back ones would get extended once the header is in the ceiling, nice and tight to the header.

    Does this make sense?
    Yes, I think I am following you, but I would do that right where the joists already overlap (or at the ends of the shorter ones) even though that might mean opening up a bit more of the ceiling you are possibly hoping or trying to leave alone.

    Edit: Also, the 3.5" header thickness is really only a convenience for making a header match wall thickness where 3" would be fine for what you are doing above the ceiling line. What you are essentially doing there is framing an opening like for a stairway, then closing it back up by also attaching joints on the other side of the double.
    Last edited by leejosepho; 07-23-2013 at 09:13 AM.
    "Great minds discuss ideas, average minds discuss events and small minds discuss people." --Eleanor Roosevelt

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    DIY Junior Member mikeangelini's Avatar
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    Quote Originally Posted by leejosepho View Post
    Only for the width of that area under three joists?


    Yes, I think I am following you, but I would do that right where the joists already overlap (or at the ends of the shorter ones) even though that might mean opening up a bit more of the ceiling you are possibly hoping or trying to leave alone.

    Edit: Also, the 3.5" header thickness is really only a convenience for making a header match wall thickness where 3" would be fine for what you are doing above the ceiling line. What you are essentially doing there is framing an opening like for a stairway, then closing it back up by also attaching joints on the other side of the double.
    Yes, only for about 4 feet/ 3 joists. I am looking to widen the hallway and have the ceiling smooth. Hence the header in the ceiling and the joist hangers.

    I could put the header where the joists already overlap, but that would not eliminate the entire wall that bumps out into the kitchen. I am looking to achieve 3 improvements at the same time with this:

    Smooth center hall ceiling.

    No annoying bump out into the kitchen. (Seems like it was only there to jackstud the header I am trying to get rid of.

    Widen the center hallway. (at this point, if I solve the other issues, I get that one for 'free'.

  14. #14
    Electrician Chris B.'s Avatar
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    So that's what you do when the framing apprentice cuts one of the ceiling joists too short.

    I don't think anyone is going to give you a definitive answer because either they don't know or they want to be paid to work out the details. As I see it you have three options:

    1. Hire an engineer to calculate and provide a drawing of how to extend the three joists
    2. Sister or replace the entire 2x10, that way you don't really need to do any calcluations (you don't want to do this)
    2. Sister the existing 2x10s with 2 more 2x10s on either side of each existing 2x10 and add blocking in-between between the new beam above the wall opening and the end of the existing short joists (your plan). The trick here is to figure out how much the new 2x10s need to overlap the existing ones and what nailing needs to be provided. That's what you pay the engineer for, so you don't have to do step #2. Remember that the entire load has to transfer to the sistered 2x10s so you probably need to go back further than you think and drive a lot of nails. It becomes even more important to do this right since three joists side-by-side are affected.

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    DIY Junior Member mikeangelini's Avatar
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    Thanks for the input so far.

    I am leaning toward plating both sides with 2 x 10 about 4' 6" back.

    Carriage bolts staggered every 8 inches, with a lot of PL Premium in between both sides.

    I would go for almost complete coverage of construction adhesive by pumping a lot out, and clamping the whole thing together to spread the glue.

    I would add in nails or Spax screws as well. I am concerned about splitting the joists by using too many nails though.

    The joists look to be in good shape.

    The more I think about it, I am tempted to just pull down the drywall to the back wall and do it right with a sistered full length board.

    This project keeps getting bigger.....

    I think this would work though.

    If I needed an extra 12 inches even, I wouldn't do it. But for 7 inches...

    I worry that it might squeak or sag over 40 years though.

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