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John Henry
Replace a broken floor joist
John Henry

Im remodelling a 1st floor room that was once a garage.After taking down the sheetrock on the ceiling ,i noticed a 2x8x12 floor joist was sheared in 2 places not giving anymore support. At one of the broken spots on the joist it looks like its sagging onto the ductwork.Iv purchased a new 2x 8 x12 and want to replace the broken joist.The broken joist supports the 2nd floor, subfloor +hardwood floor.This looks within my realm to replace it.My 1 st big question is ,when i take out the broken joist ,is it nailed from the 2nd floor when they installed the hardwood floor?(into joist).and if so how do i remove the joist if its nailed into from the 2nd floor .Could use some help.Thanks.

HandyAndyInMtAiry
Re: Replace a broken floor joist
HandyAndyInMtAiry

John
Most likely there are no staples from the hardwood floor in any joists. If the joist runs parallel to the hardwood planks, there would be a slight chance, but that is a long stretch. You may see some nails from the sub-floor that are attached. Hardwood flooring is nailed in place with staples or something like ring shank finish nails. And they should not be using nails long enough to reach the joists.

Take a sawz-all and cut the joist as close to the sub-floor as you can get. That will cut all the nails/screws that are attached to that joist. Then use a hammer and small cat claw pry bar to remove any remaining pieces of the old joists. Basically anything that you can to get the old, small pieces out. Just have to be careful and not pound the old nails back up, as they will want to list the hardwood floor. Take some nail cutters and cut them off flush with the bottom of the sub-floor. Replace any ducts that are bent, or damaged.

If it were me, I would sister or replace all of the joists with 2x12s I am in the process of adding new/replacing/sistering them in my own home. My house was built with 2x12s, but they are really old, and dry, so that are all reaching the large beams that run down both sides off center of the house. The nails are rusty and there was no such thing as joist hanger back then. The nails are always very brittle. I am using joist hangers on each end of the new ones, and replacing the old ones that are split or cracked. I am also putting the new joists on 12 inch centers, not 16 inch centers. I want there to be no questions when I put in a huge stove that weighs over 1200 pounds, knowing that the structure will hold up the weight.

I am spending more on Liquid Nails, nails for the air nailer, and joist screws and joist hangers than I have on the new joists. I don't mind spending it, for what I get back out of it in the long run. The floors are nice and level and nothing is moving.

Handy Andy

dj1
Re: Replace a broken floor joist
dj1

Sister a new joist and you won't have to go through the process of cutting all fasteners from the subfloor to the broken joist.

The new joist should extend the entire length of the old joist. You may have to raise the floor where there is sagging, to allow the new joist to get in place. Then fasten the old joist and the new joist together.

HoustonRemodeler
Re: Replace a broken floor joist
HoustonRemodeler

Sistering is the way to go.

A. Spruce
Re: Replace a broken floor joist
A. Spruce
HoustonRemodeler wrote:

Sistering is the way to go.

Another vote for sistering

HandyAndyInMtAiry
Re: Replace a broken floor joist
HandyAndyInMtAiry

I am all for sistering the joists together. And that is a great way to do this. But you cannot use screws, you must use nails. 16 penny size preferably and a good coat of liquid nails to help keep the two joists fastened together.

Screws do not have the tinsel or sheer strength. They will sheer off. That is why you must use nails.

Handy Andy

Sombreuil_mongrel
Re: Replace a broken floor joist
Sombreuil_mongrel

Our structural engineer specs these specifically for sistering. For 2x material the 2 7/8" length is used.
http://www.fastenmaster.com/details/product/headlok-heavy-duty-flathead-fastener.html
They are pretty amazing screws. We have bought them by the 500pc bucket for some jobs.
Casey

HandyAndyInMtAiry
Re: Replace a broken floor joist
HandyAndyInMtAiry

You know, I have read about those screws. I love the thought of having the ability to use screws instead of an air nailer. I am going to do more research on them, and see if the structural engineer here gives them an OK. If so, I will start using them.

Thanks for the advice.

Handy Andy

MLB Construction
Re: Replace a broken floor joist
MLB Construction

another vote for sistering.

how i would go about it......cut your new joist to the same length as the old one. liquid nails all over the side of the new joist. put the new joist in place, crown side up, and put one nail at each end either toenailed into the rim joist or into the old joist right by the end. now jack up the old joist until the bottom of both are equal. throw in a few nails to hold things in place. then screw (with the proper screws) or lag bolt the two joists together.

the main reason for sistering instead of replacement is to not disturb the floor above. if the subfloor is screwed into the old joist instead of nailed, it would be a nightmare getting the old joist out.

good luck and keep us updated.

HoustonRemodeler
Re: Replace a broken floor joist
HoustonRemodeler

Tinsel doesn't have any strength at all. The mylar or the real lead stuff.

Tensile strength is another matter.

;)

Mastercarpentry
Re: Replace a broken floor joist
Mastercarpentry

Screws are acceptable for this work, just not sheetrock screws which are hardened and therefore more brittle. I use coated deck screws or stainless screws and the inspectors here love it. Don't forget to glue it too.

Phil

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