# Cracked Floor Joist - what to do?



## Knucklez (Oct 21, 2007)

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?


----------



## Termite (Apr 13, 2008)

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.


----------



## Termite (Apr 13, 2008)

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.


----------



## Knucklez (Oct 21, 2007)

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


----------



## Knucklez (Oct 21, 2007)

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.


----------



## Termite (Apr 13, 2008)

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.


----------



## Knucklez (Oct 21, 2007)

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.
[URL=http://img33.imageshack.us/i/joistoutsidelookingin.jpg/] 
[/URL]


----------



## Knucklez (Oct 21, 2007)

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.

?


----------



## Knucklez (Oct 21, 2007)

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).


----------



## Knucklez (Oct 21, 2007)

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


----------



## Knucklez (Oct 21, 2007)

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


----------



## Scuba_Dave (Jan 16, 2009)

Old joist is probably old wood - thicker & taller then today's stuff


----------



## Knucklez (Oct 21, 2007)

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.

http://img85.imageshack.us/i/joistcrack.jpg/


----------



## Maintenance 6 (Feb 26, 2008)

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.


----------



## Knucklez (Oct 21, 2007)

you're right, the ledger is cut. don't know why - old house charm :huh:

but many of the joists are not supported by the ledger, rather the weight is delivered to the TOP of the center beam. i wedged in some wood just yesterday between the joists and the ledger board. 

so this new sister board might be the only board on that ledger. the nails that hold the ledger to the beam are huge.. the head of the nail is the size of a nickle. there is one in the center of the ledger every 16" or so.

Knucklez


----------



## Knucklez (Oct 21, 2007)

by the way Maintenance 6, i like your idea about sandwitching the cracked joist. in fact, this was my original plan, but then i found the header piece connecting to the cracked joist and so sandwitching is not possible unless i do a lot of reorganization. maybe a later date.

for now, i am still left with the 2 questions i posed earlier. any comments on these?

Knucklez


----------



## Knucklez (Oct 21, 2007)

so i am turning the jack just 1/2 turn per day to raise the cracked joist. i would like to raise the joist a full 1/4" from where it is right now and then scribe the new joist a little more to meet half way. hope that is not too much?

its kinda scary when you turn the jack and you hear "pop", "squeek", from the floor(s) above you 

hopefully some more pros can look at all the pictures i recently posted and provide additional commentary.

Knucklez


----------



## Scuba_Dave (Jan 16, 2009)

Just a thought
Do you have any other temp supports anywhere else?
Or just the one post?


----------



## Knucklez (Oct 21, 2007)

ya, i was just thinking the exact same thing. i could use another one where the header meets the cracked joist. the header meets the cracked joist about 12" from the crack.. so the jacks will be fairly close together. 

unfortunately the bottom of the header is not flush with the bottom of the cracked joist.. old house charm .. so i can not bridge the two pieces of wood with the single jack. so i'll put this 2nd jack only on the header piece (but near the connection to the cracked joist).

then it will act like a backup in case the first jack fails. and i can slowly crank them both up.. not sure if the weight will split 50/50, but it will be something like that. 

jacks are cheap, $56.. and i can always use them in the future as permanent support columns. 

thanks for the prompting, i'll do that tomorrow.

Knucklez


----------



## Knucklez (Oct 21, 2007)

Maintenance 6 said:


> 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.


i read about it here: "Wood Frame House Construction" By L. O. Anderson. see page google books, page 24 - quick link HERE.

Knucklez


----------



## Knucklez (Oct 21, 2007)

well, job's done now. i put in *two *2x8 sister joists, spanning from foundation wall to center beam. i also used construction grade adhesive and 1/2" dia. 6" long hex bolts (UNC 5) with washers. 

i went with the bolts in the end because it really wasn't any extra work for a much more secure connection. also, my situation was a bit different because of off dimensional lumber and amount of scribing i had to do (old house charm). so i wanted the extra strength in the bolts to help compensate.

i eased the weight off the jack and nothing moved at all.. so that's good! put a 4' level on the floor above and it is a marked improvement. not perfectly straight (probably impossible in this house, and you might not want to over do it anyway because of historic house settling of _other_ joists) .. but pretty much is a nice solid straight floor now. :thumbup:

oh.. and i added two 1/2" lag bolts with washers in the ledger to beef it up a bit since, as an observant member pointed out, the ledger was cut and probably would benefit from some extra strength. i had to use a 3' cheater bar to turn the socket wrench .. lots of bit in that lag bolt!!!

Knucklez


----------



## Maintenance 6 (Feb 26, 2008)

Knucklez said:


> i read about it here: "Wood Frame House Construction" By L. O. Anderson. see page google books, page 24 - quick link HERE.
> 
> Knucklez


Ahhhh. Space under the notch, not at the ledger. I misuderstood where you planned the space. Good idea on bolting the ledger. The space is to allow some shrinkage of the joist without placing the joist load on the tab. Without the space, as a joist shrinks it will lift off of the ledger and place load on the tab. That will cause the joist will split at that location.


----------



## Captain.Sassy (Jun 17, 2010)

Hey Knucklez,

If you're still around...

I'm in Ontario too, and about to undertake a similar repair to this one (though my joist isn't in quite as bad shape).

I was wondering if I could perhaps ask you a few questions re. where to get materials etc.?

It looks like you've got a single piece steel jackpost there. All the ones I've been able to find stocked so far are telescoping jackposts, and not designed for permanent use. I was planning to leave the jackpost in place after jacking up and sistering the joist, just for added support, so someone in my thread on this told me I'd better get a permanent one (the permanent ones all seem to be single piece, from my google experiences.) Where did you buy that?

Did you end up leaving the column in place, or removing it and just letting the new wood do the work? If the former, did you put a new footer in at the base of the column? 

Also, is this the kind of repair that comes under the building code? I know structural modifications need to to have a permit, but I figured this wasn't so much of a modification as a reinforcement of the existing structure.

Any tips would be really welcome!

(If you're still around, that is!)

Cheers,
CS


----------



## Knucklez (Oct 21, 2007)

hi CS, yea i'm still around. i'm not a pro, so you'll have to take my advise with a grain of salt.

my jack posts i have no idea if they are for permanent use or temporary. what exactly is a temporary post anyway, if it can hold the weight for a day it can hold the weight for a lifetime. i bought it from home depot, on the box it said rated for 9000 lbs. also, the 12x12 wood beam down the center of the house is held up by a tree trunk in the middle (wow! old eh!?) and two of the exact same type of jack stand on each end (but with proper footings with rebar and jack posts bolted in). this was done by a previous owner. looks like good work. it is obviously for permanent installation - yet it used the exact same jack post. not sure if this is "code" or not, but seems to work well for a long long time.

use a 4' level to make sure it is straight on both sides. it is round, so hard to find the "sides" but you know what i mean. 

raise the cracked joist slowly. 1/4" turn per day once you get the weight on it. my floor was sagging a lot .. i mean, it was 90% cracked through the wood and was down maybe 2" total. .. maybe more. so when i slid in the sister joists (two 2x8) i had to jack up the broken beam a lot. it was SCARY to be under all that hearing "pop .. squeak .. " as it gets jacked up. i happen to have the drywall open on some framing above that floor. when i looked at it, i could see the 2x4 framing starting to bow due to compression (jacking from below). wow!!! so i put in two 2x4 plus some other framing members near by under the stairs etc.. so it would be stronger. again with the nails and the glue. for glue, i am talking about construction grade adhesive which comes in a caulking gun.

and i did not jack up the entire way to level out the broken joist.. it just seemed too far. i leveled it up a bit so the slope isn't as noticeable at all. maybe the floor is not perfectly level, but i'm in an old house and none of my floors are level. 

my jack posts are now gone. i SLOWLY unscrewed the jack posts to put the weight of the house on the new sister joists. when i had 1/16" inch gap between wood and jack post i left it like that for a few days just to make sure it was strong and holding. then i removed jack post completely.

my concrete floor is 2" thick. it is not good for proper support of jack post. you need a real footing for permanent solution. how i was able to hold the weight of the house for the few days without cracking the 2" cement is probably a testament to the compacted soil/clay/rock under that concrete. 

for permit questions you should call your city building department and see what they have to say. every city can be different.


----------



## Captain.Sassy (Jun 17, 2010)

Hey Knuckles, thanks for sharing.

I talked to an engineer yesterday and he said not to worry too much about my crack...either use some steel plates or else a couple of pieces of wood to sister it with some bolts and then keep an eye on things for a year or so. No need for posts of any kind at the moment. So that was some good news.

Cheers.


----------

