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Old 09-04-2009, 11:26 AM   #1
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Cracked Floor Joist - what to do?


old house = can of worms..

so i decided to remove a floating subfloor in the powder room because it is ridiculous to step > 2" to enter the room. what i found under it was oak strip (same as the rest of the house) over top 1" thick tonge/grove pine plank subfloor (original to house).

then i discovered why there was this false floor...
it was hiding 2 huge holes.
ps. the floor joists run left to right



... but it gets worse
you see that metal? it is stapled to the underside of the floor. no idea why it is there.. but it does show that the pine plank subfloor is cut. so the subfloor is nolong supported by the joists.. being cut. strangely, i stepped right on that spot and the wood didn't break or anything.. strong stuff.


so far.. everything is totally fixable. so i go to the basement to see.
here i am in the basement looking UP at the metal strip.



and it gets worse..
the floor joist is cracked (the one that the sheet metal is stapled to).


and



ps.. the plumbing shown in the picture is not in service. it is just dangling there and can be removed at any time.

Knucklez

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Old 09-04-2009, 11:29 AM   #2
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Cracked Floor Joist - what to do?


what i thought was...

use a cold chisel and big hammer to smash through the stone right beside the cracked joist. so i can see outside. then, from outside, slide in a sister joist of similar size. keep sliding it in until i reach the center beam (12x12 wood) which is about 8' away from the stone foundation wall you see in the picture above. then lag bolt these 2 pieces of wood together with a staggered pattern, 16" apart.

use a jack to lift the broken joist at its break point, until it is level.. then install sister board. ??

the house does not have a rim joist (right name?), so this method is actually possible.

what do YOU think?

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Last edited by Knucklez; 09-04-2009 at 11:44 AM.
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Old 09-04-2009, 05:07 PM   #3
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Cracked Floor Joist - what to do?


Yeah, I think you're right on track. That might be a stress failure because it sure looks like one...The wood cracking perpindicular to the grain structure is fairly indicative of stress. So it does need to be replaced/sistered, not scabbed. If space is challenging I think your idea to remove a little masonry to slide a new one in is a good idea.

I can't tell what that metal piece is really doing. Is it supporting floor boards? If so that's pretty easily fixed by adding some 2x ledgers to the joist to support the floor boards to the joist. Sounds like you've got that covered.

Is that knob and tube wiring in the last pic? Sure looks like it. Assuming it is abandoned and no longer live? Might be a good idea to put a tester on it before doing your framing work jsut to be safe. K&T wiring systems can get pretty hairy.
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Old 09-04-2009, 05:10 PM   #4
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Cracked Floor Joist - what to do?


By the way, no need to use lag bolts when sistering the joists. Actually I wouldn't. If you want to bolt it use carriage bolts or trusslock screws. I'd suggest some 10 common nails and just nail the heck out of it. Construction adhesive is also a good idea to minimize the potential for any squeaking. Nails and glue is how 90% of the engineered sistered joist repairs I see are specified.
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Old 09-04-2009, 10:01 PM   #5
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Cracked Floor Joist - what to do?


thanks for the confidence building.

i guess what i am most concerned with is disturbing the stressed joist. normally, in a house, you can relieve the joist support temporarily while you are sistering in a neighbour because the rest of the joists (16" OC in either direction) will take up the burden while you fix the one.

but in my case, how strong are the other joists? they are not in the greatest shape either (though there is no obvious signs of fatigue like that shown above).

so i want to go slowly.

1) i'll slip in a sister joist beside that one shown above but not nail it in yet.

2) then, go to the joist beside it where it is also questionable and do the same.. also with no nails yet, but the new board is beside the joist.

3) go back to the first joist (shown in pictures above) and jack it up to level .. glue & nail the sister joist that is already there.

4) releive the jack so the new board will take up the weight.

5) go to joist # 2 and jack it up and nail/glue the sister joist that was already placed there in step 2.


that way, while the weight of support is shifted away from this joist under work, it will go to the neighbouring joists that at least has a known piece of solid wood (the one i just put there!).. no this wood is not supporting the weight (yet) but at least it is there and will respond during any drastic emergency.

yes.. i am very paranoid... way over killing it and over worried. it is just in my nature.

ps. that is definately not active knob and tube. it doesn't go anywhere. all the old stuff was replaced with modern before we even moved in.

thx for your support and dedication to this website. we always appreciate honest advice.

Knucklez
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Last edited by Knucklez; 09-04-2009 at 10:11 PM.
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Old 09-04-2009, 10:06 PM   #6
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Cracked Floor Joist - what to do?


the metal piece is thin piece of sheet metal. it is not supporting anything. the floor boards are just cantilevered since they are cut just before they reach the supporting joist (the one that is cracked).

but like i said, i stepped on that floor board and it didn't even budge. and it has a HUGE hole in it on one side and not supported by anything on the other side! solid stuff. i will lay a piece of 3/4" ply on the floor above it just in case someone walks there while it is being fixed. i will fix this once the sister joist is in place and i have something solid to build some framing with, as you suggested.

also, we had piano movers come in a couple of years ago. two beefy guys and an upright piano rolled right across that joist and it held.. even though it looks severely compromised.

so i have some faith that there is strength there. but i still want to fix it so it is as good or better than new.
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Old 09-04-2009, 10:34 PM   #7
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Cracked Floor Joist - what to do?


I think your plan is fine. Just don't overdo it when jacking. You may not get all the deflection out of the joist but getting some of it out will get the load onto the new joist. Depending on how severe the sag is once you've jacked it, it may be necessary to scribe the contour of the deflection into the top of the new joist. Just depends.

Assuming there's no bearing wall or point load on the compromised joist I wouldn't have much concern with removal of it while you're doing this fix. It never hurts to support things just to be safe though.
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Old 09-27-2009, 08:42 PM   #8
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Cracked Floor Joist - what to do?


just catching peeps up on my woes.. need your advice.

here is a picture of the cracked joist being supported by a jack stand. at this point, it has been raised one full turn.. i can hear pops and squeeks from just above 1st/2nd floor as it is being raised.


here is a picture of the original joist (the cracked one) with a jack supporting it.


here that same cracked beam is resting on the center beam for the house.


this picture was taken outside, looking IN to the basement... where you can see the same cracked joist. the foundation wall is 18" thick, rubble stone.

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Old 09-27-2009, 08:48 PM   #9
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Cracked Floor Joist - what to do?


then, i slide in the sister joist. it is bought new, 2x8x12 (to span 10.5'. the new board is 1/2" thinner than the original, and 1/8" shorter in width..

so.. QUESTION 1: i have 3 choices due to wood being not the same width.

a) i can rest the new joist on the sill.. but it won't quite reach the wood foor.

b)i can push the wood up and nail it in place but it won't quite reach the sill (and then not really work as load bearing support)

c) push the wood up to floor level. then put some shims under it between new joist and sill.. and then take the jack out.

i am leaning towards c) .. or a) but with 1/2" carriage bolts.

?
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Old 09-27-2009, 08:51 PM   #10
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Cracked Floor Joist - what to do?


but just to get a feel for the fit.. i went outside and slid in the new board. but due to the floor being low due to cracked joist.. i can not slide the wood in smoothly .. it hits the floor.

so i scribed the wood, took off about 1/2" wowza..

but i was able to slide the wood all the way to the beam.. but looks like its still too low. i'm going to cut the wood where it is marked with blue pen "X". then there will be a gap here between the new joist and the center beam. according to some books i read, there is SUPPOSED to be a gap here anyway (don't know why).

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Old 09-27-2009, 08:53 PM   #11
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Cracked Floor Joist - what to do?


with the joist still not in position correctly, i took a snap shot of how the new joist is lining up with the original joist..

picture taken near the jack stand. see how much lower the old joist is? granted, it is 1/8" wider.. so take that into account. but looks like i need to jack it up another 1" ... or scribe the sister joist even more?

QUESTION 2) how much can i jack this joist up? it is servicing a point load (stairs from 1st floor to 2nd floor). additionally, it is taking quite a bit of load from neighbouring joists that do NOT extend to the exterior wall.. but rather from center beam to some 2x8 wood.. which runs from end of house (rim board) to THIS cracked joist (perpendicular) and then nailed in place

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Old 09-27-2009, 08:58 PM   #12
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Cracked Floor Joist - what to do?


i plan on running another 2x8 sister board just to overkill it. there is a lot of stress on this joist in the house for whatever reason.. so want to have it extra strong.

once the first sister joist is looking good, i'll glue & nail it in. then the second sister joist will come in beside the first and will be glue nail. then i have three 1/2" carriage bolts (6" long) , so i'll drop them in equa distant along the board.. and snugg it up real good.

then take the jack out .. slowly
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Old 09-27-2009, 09:00 PM   #13
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Cracked Floor Joist - what to do?


Old joist is probably old wood - thicker & taller then today's stuff
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Old 09-27-2009, 09:11 PM   #14
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Cracked Floor Joist - what to do?


yep.. good thing it was strong, lot of weight on this joist.

here is the plan of how the structure is laid out in this area.

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Old 09-28-2009, 08:35 AM   #15
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Cracked Floor Joist - what to do?


Maybe you should think about running the second new joist on the opposite side of the cracked one. Then bolting through to sandwich the broken one in between. The point load on the single joist is likely what cracked it. In the picture with the blue pen marks, you said it's supposed to have a gap here. I've never heard of that and I wouldn't put one there. Also it looks as though the ledger on the beam ends just past your old joist as though it was cut off. That is probably not good either. You might want to consider throughbolting the ledger to the beam. With the holes through the floor and cut off boards, the whole thing looks like someone put a commode in here and cut things out of the way without any consideration for the remaining structure. From what you've said it sounds like adjacent joists were cut off and headered. It might be a good time to evaluate whether they still need to be and perhaps take out the headers and sister those joists to restore them.

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