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Cracked Floor Joist Advice


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09-22-17, 10:30 PM   #1  
Cracked Floor Joist Advice

hi !

so i was in the crawl space (really fun) replacing some duct work that was old and torn up. and unfortunately i found a crack in a floor joist which surprisingly corresponds to a depression in the flooring right in the hallway. now it all makes sense. lol

the crack is about 3 ft in length with the widest gap of 1". it starts about 24" from one end of the joist. i believe the joist is 12ft long.

any chance i can just jack it up and strap on some simpson strong ties (see pic) with hanger nails and call it good. might be rather difficult getting sister joists of any length down into the crawl space. the access to the crawl space is a small opening inside a closet.

or do i need to call foundation people?

would welcome any advice. haven't really had too much experience in crawl spaces and floor joists.

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marksr's Avatar
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09-23-17, 03:41 AM   #2  
While a strong tie would help I'd think it would be better to jack it up and sister a new joist onto the cracked one, preferably one that would span the distance from the foundation wall to the beam in the middle.


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09-23-17, 03:45 AM   #3  
I don't think that you need foundation people. Try the jack idea with a Simpson Strong Tie. Just don't rush it. Don't jack it up fast like a car.

 
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09-23-17, 05:04 AM   #4  
No, that is not what those sort of ties are for. (Tie plates like TP37 or TP411 are not load rated) Marksr has given you good advice, that's the way you should go.

 
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09-25-17, 07:37 AM   #5  
Another idea although more time/materials and overkill.
Create a short header (2x10) that would span perpendicular over 3 joists plus a few inches.
Get two post/screw jacks and concrete pads. Dig shallow holes under the two adjoining joists and fill with gravel (soil type will determine depth - I am on rock so I can only dig about 6 inches in my crawlspace). Tamp it flat. Using the header and jacks, jack up the cracked joist until level with the other joists- don't jack the others up. Get as long of a section of joist as you can in there and glue/nail it to cracked joist. Leave it all down there.

 
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09-25-17, 07:45 AM   #6  
A header can't hurt but I don't understand how gravel helps. It's not compactible.

 
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09-25-17, 08:08 AM   #7  
RWhen a single joist is broken, you can cut it on either side of the break and head it off to the single joists on its left and right. Then replace the short section you cut out which is now between the headers. You dont need any posts if you do it that way.

 
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09-25-17, 12:14 PM   #8  
@Donato_ - The fact that it can't be compacted is why I would put it there. Kind of a compromise between sitting the 2" pad directly on the dirt and pouring an actual footer. Again though, my suggestion is definite overkill.

 
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09-25-17, 01:56 PM   #9  
A header with footings maybe overkill but it would be a permanent solution.

 
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09-27-17, 09:19 PM   #10  
so far so good. i bought two 20 ton bottle jacks. have jacked it up 1/2" over the last 3 days. i've been able to get a 60 inch board in the crawl space so hoping to be able to get a 84" inch, 2x8 in there. that will span the width from one girder to the other girder. plan on using liquid nails to temporarily attach them together, clamp them down and install carriage bolts,washer, lock nut in a zig zag pattern.

a couple of questions:
1) do i need to add a sister joist to EACH side of the cracked joist? or can i get by with just one?
2) i came across a page that suggested the carriage bolt zig zag pattern should be 6" apart, is that about right?

thanks again.

 
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09-28-17, 03:27 AM   #11  
Unless there is some undue load on the floor above a new joist sistered to one side is enough. I'd glue and nail it, then add some bolts here and there ...... but I'm a painter, not a carpenter.


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10-02-17, 11:21 AM   #12  
hello,

thanks for all the input especially since my background is not in construction.

not sure if this is the correct way but wanted to give an update on what i did and maybe someone can use i what found to be helpful if they have the same situation.

i was able to get a 84" section of 2x8 down into the crawlspace. this allowed me to span from one girder to the other girder. i previously jacked up the splitting joist by 1/8 to 1/4 inch per day. it took me about 5 days. the original gap was around 1" at the widest point. i used two 20 ton bottle jacks i bought from harbor freight with a 3 ft section of 2x4 to jack/support the joist.

after it was jacked up, i couldn't slide in the 2x8, so i had to notch about an 1/8 off one end to get it in there. i also shimmed whatever i could to make it as tight as possible.

i applied a bead of Loctite PL Premium (read somewhere that's what you're supposed to use, it's a little more runny than Liquid Nails exterior/interior). clamped the new 2x8 to the old joist.

originally i wanted to use carriage bolts but found that they easily stripped the wood and would basically just turn and turn. so i switched to 1/2 hex bolts 4" long with washers on both sides and a stop nut. i did 12 of them across the section and drilled about 2.25 inches from the top and bottom edge (some online posts suggested 2inches from the edge, others suggested 2.5 inches from the edge).

i let it sit overnight and removed the bottle jacks the next day. replaced the insulation.

the good news is i can't feel the dip in the hallway anymore.

thanks again for the advice.

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10-02-17, 11:48 AM   #13  
Looks great!

PL Premium is some nice stuff.

 
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10-02-17, 02:16 PM   #14  
In the words of Smokey Robinson, I second that emotion. Looks great.

 
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10-02-17, 02:56 PM   #15  
..... and more importantly it looks effective! good job


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