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Old 08-01-2012, 05:43 PM   #1
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Sister Joists Without Leveling Floor


Hi guys:

I am remodeling my 100yr old farmhouse and here are the facts:

The floor joists on the second story of the house are 2x6s spanning 15'. Obviously, the second level flooring has sagged (over the course of the past 50-60yrs). I do not mind the sagged flooring, but I want to prevent it from getting worse.

I called a structural engineer, who advised me to sister 2x10s to each of the 2x6s to add the required stiffness. I cannot add a beam down the middle as it would have to span a 30' gap, and would require far too substantial drop in ceiling height.

I do not want to level the upstairs flooring by jacking the 2x6s because I am afraid it would likely break apart all of the tile, drywall and plaster upstairs.. and possibly rupture pluming and other things that have settled for 50 years.

Anyway, my plan is to sister the 2x10s onto the 2x6s. However, the 2x6s are sagged, which means the 2x10s will not mate up perfectly with the 2x6s.

So how do I attach the 2x10s to the 2x6s ? Do I just align the 2x10 so that the top of the 2x10 hits the middle of the floor (the low part) and notch the ends so that they can rest on the sill? This will leave gaps between the subfloor and the 2x10 starting at the middle of the new joist and extending to the ends. Do I then just fill in the gaps with a shim cut to fit?

Thanks for the help.

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Old 08-01-2012, 05:53 PM   #2
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If this is to the second floor joists, what can be seen of the ceiling from the first floor room?
Can your ceiling height accommodate this 4"+ difference in the lower room?
If you can accommodate all this , you can lag bolt the joists where they sister and no need to shim to the floor underlayment.
Mike

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Old 08-02-2012, 01:29 AM   #3
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As per Woody
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Old 08-02-2012, 08:23 AM   #4
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Sister Joists Without Leveling Floor


Mike: I have opened up several holes in the ceiling (I am talking about the 2nd floor floor joists) to view the joists. My ceiling height is a solid 9', so losing 4 inches won't be terrible.

Tony: your drawing shows exactly my "plan". Is this the best way to go about sistering the joists? Wont the floor only be supported at the mid point unless I add shims?

Also, the engineer did not spec the sistering to have the bolts. Its indicated to require only 12d nails at specific spacing. Should I use the lag bolts too?
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Old 08-02-2012, 08:36 AM   #5
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Sister Joists Without Leveling Floor


Apparently you have the flooring pulled up in the second floor and are ready to drop in the sister joists. I highly recommend jacking up the center of the joists from the downstairs some. You do not need to get it up to perfectly level just to get out some of the sag. After all of the banging and beating to get the new joists in you will most likely crack some of the plaster on the downstairs ceiling anyway so why not jack them up as you go? unless you have plumbing cut through joists then I do not see how plumbing will be affected by raising the joists back up, if the plumbing was installed level with the joists and then both plumbing and framing settled over time then the plumbing would have settled as well and possibly need fixing along with the joists anyway.

Really your only option without demolition of the first floor ceilings is to set the new joists onto the outside wall plates flush with the underside of the old joists along the outer walls. If the old joists remain sagged and settled that will only show in the first floor ceiling and not really affect the new joists as they will be 3 or 4 inches taller sticking up into the room, just nail them right next to the saggy ones. I do recommend jacking though as the end result will be worth it save for a few extra plaster cracks.

Last edited by hand drive; 08-02-2012 at 08:38 AM.
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Old 08-02-2012, 08:45 AM   #6
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Sister Joists Without Leveling Floor


Hand Drive - I've actually got the opposite situation. The second floor is completely in tact. I am in the process of ripping out the first floor ceiling to expose the 2nd floor floor joists.

I will have to get the sister joists in from the bottom, which I am hopeful will not be impossible.

I might be able to jack each joist up 1/8" or so, but I really don't want to destroy the plaster work on the second floor. It is actually in beautiful shape, and I would hate to have to re-do it. I am perfectly happy having the sag remain in the floors, so long as it doesnt get worse.
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Old 08-02-2012, 08:56 AM   #7
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Sister Joists Without Leveling Floor


Not sure if this will work in your case but what we have done in the past is add what amounted to a notched ledger the width of the new joist to the walls where the new joist will be attached with lag bolts set between where the joist would sit.

We used LVL's not reguler wood. There stonger per ft. then reguler lumber.
We used LVL hangers to attach just one side at first, and screws to temp to hold the new joist up in the middle, we then built a beam to lift the center, once in place we removed the screws and lifted once level we attach the other side with LVL hangers and through bolt the LVL's and the old floor joist together. Then remove the temp. beam.
It took 1-1/2 of sag out of the floor, there was 0 bounce when done.
It was a plaster and lath home with hardwood floors and nothing cracked and no gaps opened up in the floor.

I know someones going to jump all over this idea, but it worked, the floor never moved again, and the sheetrock that went up and never cracked, plus the customer was thrilled with the way it turned out.

Last edited by joecaption; 08-02-2012 at 08:58 AM.
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Old 08-02-2012, 08:58 AM   #8
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Quote:
Originally Posted by patented View Post
Hand Drive - I've actually got the opposite situation. The second floor is completely in tact. I am in the process of ripping out the first floor ceiling to expose the 2nd floor floor joists.

I will have to get the sister joists in from the bottom, which I am hopeful will not be impossible.

I might be able to jack each joist up 1/8" or so, but I really don't want to destroy the plaster work on the second floor. It is actually in beautiful shape, and I would hate to have to re-do it. I am perfectly happy having the sag remain in the floors, so long as it doesnt get worse.

ok, I had it all backwards. Jacking at the center of the rooms floor span will in no way affect the second floor walls as they reside on the outer edges of the floor system where nothing will move.

Once you have exposed joists and demo is done you probably want to measure at the edges and pre cut all of the new joists and set them up in the joist bay laying flat on their sides, then get a jack system in place. once jacked up to as level as possible tip the new joists up into place. this sounds easy and is easy to type here but will require some forethought and planning. you want to try and not notch that much out of the ends of the new joists also as the strength is compromised.

pics would be great also once you have the floor framing exposed and how the bearing connection is along exterior walls.

re edit, might be best to lay two 2x6 flat on the first floor ( bottom temp wall plate) perpendicular to the joist system in the middle of the room right next to each other. put up a temp beam to the ceiling and use one of the 2x6 to jack up off of. once you have the ceiling jacked up and straight use the other 2x6 (bottom plate) to put a vertical 2x6 under each joist cut tightly to the 2x6 plate and up against each floor joist. after you do this to every joist, take the temp beam down and the single 2x6's under the joists should hold the ceiling nice and level while you do your sistering. get all of your sistering in and nailed off good before taking down the vertical 2x6 singles. if you try and go in and jack one joist at a time it gets complicated, you have to think as a whole span that raises together.

the temp beam would in the way of adding in the sister joists because the sisters are wider than the old joists.

Also, you might want to add 2x6 splice blocks where the single studs meet the old joists or just toe nail the studs to the old joists and cut the nails later when done...

please let me know if you have any questions

Last edited by hand drive; 08-02-2012 at 09:26 AM.
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Old 08-02-2012, 08:59 AM   #9
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I didn't think about this beforehand but the way Tony relayed my thoughts in the drawing will not allow the joists to be installed with that notch in the ends unless it is dropped in from the top. You would have to use joist hangers.
Trying to give all this re-consideration........
How much sag are we talking about ?
Are the tiles installed to the floor or the walls of the second floor?
Where does the plumbing run?
I'm leaning towards "Hand drives" suggestions.....you know....if a jobs worth doing.
Give us some more specifics and lets see if we can suggest a solution for your budget.

Editing this.......doing as Joe suggest would work well. I have done similar .......he was probably writing his reply as I was doing mine.
If the floor is tiled ....this could be the deciding factor to the way to tackle this. Engineered joists are way stronger and a smaller dimension can be used.....there again cost is a factor and also the degree of bow.

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Last edited by woody4249; 08-02-2012 at 09:13 AM.
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Old 08-02-2012, 09:32 AM   #10
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[quote=patented;979655] Wont the floor only be supported at the mid point unless I add shims?

quote]

No; as long as the new 2x10s are securely fixed to the original joists, there is absolutely no need to shim under the floor deck.

If your SE says use nails, then do that. It's just that personally I would have used bolts in that situation as there is less banging and vibration; just personal preference, that's all.
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Old 08-02-2012, 06:18 PM   #11
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Sister Joists Without Leveling Floor


Thanks guys! Im going to start tackling this over the weekend.

The upstairs floor is partially tiled (marble tile) in a bathroom. The rest of the flooring is ~60yr old oak.

I'll try to take some pics if I am able.

Thanks again. You guys are a big help
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Old 08-08-2012, 04:12 PM   #12
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Ok, so the plot has thickened.

I have now gutted the rooms, and the second story floor joists, on one side of the house has a steel I-beam (turned sideways so its more of an H-beam) that lays perpendicularly across the top of the 2x6 joists. The joists have each been notched with 2 small slits to allow the bottom of the H to rest within the joists. (Can we all say WTF?) The H-beam is supported on one side by the top plate of the exterior wall of the house, and on the other end by a single 2x4.

Anyway, this now causes some issues with the possibility of sistering a 2x10 on the joists. Clearly, the H-beam cannot be moved without ripping up the entire second floor of the house, which isnt going to happen. So, can I sister a 2x10 onto the 2x6 and butt it up to the bottom of the H-beam? The "prongs" of the H-beam sit a good 2" into the 2x6 joist. So if I sister on a 2x10, only about 4 inches of the 2x10 will overlap the 2x6. Is this ok? Also, the H-beam is approximately at 50% of the span of the joists.

Anyone have any interesting solutions to this problem?

I have an SE coming back by the house tomorrow, so if anyone has some good ideas, I would like to run them past him.
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Old 08-08-2012, 08:51 PM   #13
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you do know that you can't ask something like that, WITHOUT pics, right ?
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Old 08-08-2012, 09:24 PM   #14
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I like Joe's idea because it sounds like you do not have to notch the joists at the ends. The most likely place for them to crack from weight is starting in the corner of the horizontal and vertical cut. From your sketch there would be less than 50% of the 2 x 10 left at the notch
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Old 08-09-2012, 05:48 AM   #15
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Quote:
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I like Joe's idea because it sounds like you do not have to notch the joists at the ends. The most likely place for them to crack from weight is starting in the corner of the horizontal and vertical cut. From your sketch there would be less than 50% of the 2 x 10 left at the notch
If you mean the sketch in post 3, then yes, it shows about 50% of the timber removed for the notch, though this was only a sketch showing the idea in principle (the OP can't do it this way now because he's not fitting the new joists from above).

However, although such a deep notch would not be recommened by any code for a single joist, remember that these are being fixed to existing joists. The bending stress is minimal at the bearing and the existing 6x2 would be OK to take the shear stress at that point.
The purpose of the new joists would just be to reduce bounce in the existing floor, which at 15 ft is overspanned.

Siince then, the OP has mentioned this steel beam, and I can't visualize what he means - pic would help.

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