# Floor joist replacement



## jaydubya (Aug 19, 2010)

When i bought my house I didnt have it inspected first (I know.......) and the floors are sagging. At some point the previous owner installed a beam up the middle to resupport the joists. now they are sagging to either side of the beam so I have high spots at the walls and center and low spots between. my floor looks like a big "W". After some detective work i have found that the joists are actually 2x6s that are bowed, notched, doubled, scabbed together, and otherwise compromised in all sorts of stupid ways. i want to replace them altogether. Can anyone tell me what the proper procedure is for this? Due to money reasons I need to do this myself instead of spending big money on a contractor


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## Jack Wilson (Mar 14, 2010)

jaydubya said:


> When i bought my house I didnt have it inspected first (I know.......) and the floors are sagging. At some point the previous owner installed a beam up the middle to resupport the joists. now they are sagging to either side of the beam so I have high spots at the walls and center and low spots between. my floor looks like a big "W". After some detective work i have found that the joists are actually 2x6s that are bowed, notched, doubled, scabbed together, and otherwise compromised in all sorts of stupid ways. i want to replace them altogether. Can anyone tell me what the proper procedure is for this? Due to money reasons I need to do this myself instead of spending big money on a contractor


Hey Jay,
1st off, is your basement or crawl space dry? This WILL affect the future of your new floor. You want a dry space.
2nd, your existing joists will have nails in them which will "pop" thru the floor sometime in the future if you remove the joist, but not the nails. I don't what access you have to the nails above, is the floor covered? Does it have carpeting and you can pull it back, or is it a vinyl floor covering and its glued down... Additionally the joists will be laid out such that they fall on the breaks of the floor boards, which brings up the next question, do you have T&G 1x floor decking or sheets of plywood? And lastly, what is your span?

So, here's what you want to do in a perfect world, leave the beam. If possible remove 1 floor joist and nails then replace it, one at a time, space them at 16" on center, (14.5" inside gap). For even more support put them at 12" o.c. seeing as they are only 2x6. after about 6 joists go back upstairs and nail them down, lather rinse repeat. You get the drill. maybe it sounds like a lot of work, but you can do it. In fact you may choose to double every other joist to beef up your load capacity. Lastly, look for fir, hem or Doug, both are stronger than spruce.


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## jaydubya (Aug 19, 2010)

Jack, thanks for the advice. the crawl space is dirt, probably not dry. is there a good way to make it dry? There is T&G 1xs that will be replaced with OSB. The span is approximately 20 feet with a beam down the middle. At the same time i do this, ill be removing all flooring, subfloor, and drywall and redoing the whole end of the house. ill be able to access everything from the top and bottom. I was thinking about replacing the existing 2x6 joists with 2x10s notched at the ends to fit the joist pockets. Is that a good idea or should I stick with 2x6s which I dont really want to do.


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## curt99 (Oct 17, 2010)

Jay,

If your going to strip out the floor and have complete access to replace the framing, can I assume that you are working in a single room wing? If this is the case I would rebuild the floor system using 2 girts at 1/3 the span with colunms no more tha 6' o.c.. I would replace the floor joists with new 2x6's @ 12" o.c.( I would not use knoched 2x10's because once you knotch the end, you just ceat a more expencive 2x6.

Keep in mind you need propper ventilation and insulation in the crawl area also if you need to upgrade the heat or eletrical this is a good time to do it.

Good Luck,

Curt


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## allthunbs (Jun 22, 2008)

What about when the stud wall is sitting on the subfloor at the end of the joist? How can you be sure it's getting adequate support? How do I tie into the rim joist or must I block and screw the joist end?

Why not just leave the existing joists there and sister new ones along side the old?


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## Jack Wilson (Mar 14, 2010)

allthunbs said:


> What about when the stud wall is sitting on the subfloor at the end of the joist? How can you be sure it's getting adequate support? How do I tie into the rim joist or must I block and screw the joist end?
> 
> Why not just leave the existing joists there and sister new ones along side the old?


Who's asking the questions, Ron or Jay? Same house? Do you guys know each other...or is somebody hijacking this thread?! 
Anyway, Jay, you need to keep some sort of ventilation in your crawl space so that the moisture can escape, but you can also lay down some heavy plastic, (6 mil) and cover that with a thin layer of concrete, like 2" minimum. As someone else said, (I can't see all the names while replying), notched 2x10's loose their integrity, unless you can throw joist hangers on them. Also with a 20' span, yah, use 2 beams with 2x6, or 1 beam with a 2x10. ( The beam should be a triple 2x10 over lapped with any seams placed above a column, the columns should sit on a good solid footer. Footers should be poured about 8'-10' apart and be 2'x2'x10"). Good that you can just rip out all the old floor. If you insulate the floor be sure that any vapor barrier is placed toward the heated living space. If you want the room warm, you will need to insulate, R-19 as a MINIMUM, more is better, but I don't know what environment you live in. Regarding the ventilation, one at each end covered with heavy screen, but allowing free air flow should work.


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## Jack Wilson (Mar 14, 2010)

allthunbs said:


> Why not just leave the existing joists there and sister new ones along side the old?


Because according to his description the joists are bowed, warped, scabbed together... better to just remove them than to fight with them. They now have a 'set' to them and you will never make this go away, instead the new joists will begin to follow suit.


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## bobj3 (Jan 17, 2006)

Hi Jason

You said it ( "probably not dry" ) I would say you need to fix that 1st., if it's that damp it will not help by fixing the floor...they need a dry base to support them on ..

Note they do make floor joists screw jacks just for that type of job.

========


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## allthunbs (Jun 22, 2008)

Jack Wilson said:


> Who's asking the questions, Ron or Jay? Same house? Do you guys know each other...or is somebody hijacking this thread?!


Sorry Jack & Jay, I'm reading your instructions and following them along. I see at the end of the joist the stud wall sitting on the same joists he's trying to remove and I'm wondering how to deal with that one. Then I see the rim joist. I'm dealing with something similar so I'm looking for all the info I can get.


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## Jack Wilson (Mar 14, 2010)

allthunbs said:


> Sorry Jack & Jay, I'm reading your instructions and following them along. I see at the end of the joist the stud wall sitting on the same joists he's trying to remove and I'm wondering how to deal with that one. Then I see the rim joist. I'm dealing with something similar so I'm looking for all the info I can get.


Ron you can cut some stubs of your floor joist and leave them in, or place them next to the joists you are going to replace. Of course if your floor is not in as bad condition as it sounds like Jay's floor is in then maybe YOU could sister new joists in place. Not recommended if you have conditions similar to Jay's floor.


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## sealion11 (Oct 30, 2010)

geez this quite a project # 1 2 by 6 is to small not nowing the span of the floor I can,t tell the size you need to replace this .The only thing to do if you don,t want to spend a lot of money is to put a beam on either side of the one there now. and put jack post,s in taking them up a little at a time . All this is on the space you have and with any luck at all you don,t have any rut in the wood there now Good luck frank


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## RJM (Apr 11, 2010)

Are you sure the center beam was added after the house was built? A 10 ft span (20 ft and center beam) is about the limit for 2x6 joists with 12" spacing.

Definately go with the 2x10's notched at the ends to fit the sill plates but make sure they fit snug (i.e. notches are the same size). You might want to check the alignment of the sill plates and the center beam before cutting the notches. If there is variation, you can cut each joist notch to level out the floor (a lot of measuring but worth it at the end). If you're going to do this, you might want to invest in a laser level system; you could shoot the whole floor. Also, make sure you cross brace properly. I see lots of floors where the cross bracing is not done right. The cross braces must create a straight diagonal and not be flat before bending. If I was doing this, I'd use solid blocking.

Notching the ends like this is a common practice and will increase the strength of the floor and the stiffness by a factor of 5. The reason is that the form factor for the beam is proportional to the cube of the height. Small increases in beam height increases the bending strength a lot. That the ends are notched will not significantly change this, in fact, 2x8's are probably adequate but I would go with the 2x10's (I'm assuming 16" spacing).

I hope you're doing this with a permit. If not, I would advise that you re-consider for 2 reasons. First, you get "cheap" advice, you'll know that you meet code, and you can be reasonably sure the floor will be strong enough. Second, it will cost a lot when you have to get it inspected after the fact, especially if you have to rip open new walls, etc.

I don't think you need a second center beam (I think this is what was meant by the 2 girts, which are actually something else). Just make sure the center beam, the columns supporting it, and the column footings are in good condition. 

As was mentioned, make sure the crawl space is adequately vented and water does not collect there naturally. You may need to examine the grading and drainage around the structure and make modifications if you really have a water problem. You may want to hire a foundation expert/contractor to take a look. After all, you're going to have it all opened up, so make sure everything is right while it's easier to fix.

GOOD LUCK!


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## DGK (Oct 8, 2010)

From what little information that has been given (a few pictures would be useful), we can only give you some general advise as to various methods to fix the floor joists, but you got my attention when you mentioned the crawl space probably not being dry... *if* it's not, then fixing that would be the first thing on my to-do list.

Another thing mentioned here is ventalation of said crawlspace to help dry it out and/or keep it dry, and I totally disagree with that train of thought. *IMO*, it's an outdated building practice, and the negative effects that come about from venting far outweighs any bennefits that could ever be gained. 

*If* there is moisture, then you need to figure out where it's coming from, and how to stop the infiltration. Then you can set about the business of sealing the crawlspace, and eliminating the moisture issue once and for all.

Take a look at the PDF in this link to see what I'm talking about.


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## allthunbs (Jun 22, 2008)

Jack Wilson said:


> Ron you can cut some stubs of your floor joist and leave them in, or place them next to the joists you are going to replace. Of course if your floor is not in as bad condition as it sounds like Jay's floor is in then maybe YOU could sister new joists in place. Not recommended if you have conditions similar to Jay's floor.


Marvellous. Thank you Jack.


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## allthunbs (Jun 22, 2008)

RJM60 said:


> Notching the ends like this is a common practice and will increase the strength of the floor and the stiffness by a factor of 5. The reason is that the form factor for the beam is proportional to the cube of the height. Small increases in beam height increases the bending strength a lot. That the ends are notched will not significantly change this, in fact, 2x8's are probably adequate but I would go with the 2x10's (I'm assuming 16" spacing).


Hi Robert:

I had a house built exactly the way you describe. Joists were 2x10s stretched across a 12' span, notched at the beam and rim joist and sitting on a 2x2 strip and toe nailed into the beam and the rim joist. It was like walking on a trampoline. My small dog (20 lbs.) could setup sympathetic waves and the whole room would bounce. I did two things to stop it: I put joist hangers on and blocks between the joists. I'd love to see some research on this topic.


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## Uncle Jim (Sep 30, 2010)

*floor joists replacement*

I have replaced many floor joists and believe i can give some input.
#1 A 20' width with a beam at mid-span would be a a 10' span - width of plate and beam. so approximately 9'4" to 9"6" consult span charts 2x8 will most likely be more than sufficient. I would not use 2x6 even if allowed -not enough stiffness.
#2 after notching ends use wedges against sill to force joists against bottom of plates.
#3 Bottom of joists must be supported with a joist hanger that bends over and is nailed to sill. 
#4 nail bottom plate to sill and to screw ends of joists to rim so rim can not tilt out and allow wall to kick out.
#5 Bearing walls parallel to beam can not be offset from beam more than the depth of the joists that is 7 1/2" on a 2x8. Partition walls parallel to joists should be supported with double joists.
#6 Crawl space if heated should have perimeter insulation. and sufficient air conditioning to keep dry and warm/cool. no insulation should be used in floor.
If crawl space is cold (unheated) it should have good ventilation to outside and joist should have sufficient insulation. In either case 4 or 6 mil plastic can be used as a moister barrier and either a scratch coat 2" of concrete or more simply a layer of stone cn be used to protect and keep it in place. Hope this helps.


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## bobj3 (Jan 17, 2006)

Hi 

Now this post I will 2nd..

======



Uncle Jim said:


> I have replaced many floor joists and believe i can give some input.
> #1 A 20' width with a beam at mid-span would be a a 10' span - width of plate and beam. so approximately 9'4" to 9"6" consult span charts 2x8 will most likely be more than sufficient. I would not use 2x6 even if allowed -not enough stiffness.
> #2 after notching ends use wedges against sill to force joists against bottom of plates.
> #3 Bottom of joists must be supported with a joist hanger that bends over and is nailed to sill.
> ...


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## jaydubya (Aug 19, 2010)

RJM60 said:


> Are you sure the center beam was added after the house was built? A 10 ft span (20 ft and center beam) is about the limit for 2x6 joists with 12" spacing.
> 
> *Yes, i found the jack that was used to do the "leveling" still in the crawl space. the "beam" is actually a doubled 2x6 resting on cinder blocks. that will be changed*
> 
> ...


 Answers bolded in the quote above


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## jaydubya (Aug 19, 2010)

Just out of curiosity, what Kind of material would be needed to use as joists for the 20 foot span with no beam? Would i be correct in assuming that I would need bigger/stronger joists under the part of my house that has a second story than i would under the part with just one floor?


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## allthunbs (Jun 22, 2008)

jaydubya said:


> Just out of curiosity, what Kind of material would be needed to use as joists for the 20 foot span with no beam? Would i be correct in assuming that I would need bigger/stronger joists under the part of my house that has a second story than i would under the part with just one floor?


Hi Jason:

In my neck of the woods they use floor trusses engineered and made out of 2x4s just like roof trusses. Alternative is steel beams with 2x? bolted to either side as attachment points for joists. I've also built beams of sandwiched 3x(2x12) with 1/2" plywood sandwiched between each layer; the whole thing glued and bolted with stainless bolts.


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## RJM (Apr 11, 2010)

allthunbs said:


> Hi Jason:
> 
> In my neck of the woods they use floor trusses engineered and made out of 2x4s just like roof trusses. Alternative is steel beams with 2x? bolted to either side as attachment points for joists. I've also built beams of sandwiched 3x(2x12) with 1/2" plywood sandwiched between each layer; the whole thing glued and bolted with stainless bolts.


 
You can't notch these engineered beams. The caps (2x4') need to be continuous.


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## RJM (Apr 11, 2010)

jaydubya said:


> *I thought that using notched 2x10s would increase the strength over 2x6s but have been told otherwise a few times.*


Whoever told you otherwise is wrong. 2x10's will increase the strength and stiffness of the flor about 5 times, even with notched ends.


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## RJM (Apr 11, 2010)

jaydubya said:


> *Permit, whats that?? there are no inspections here lol. I dont believe in giving the government money to allow me to work on my own property. *


Whatever dude. I guess you don't pay property taxes either.


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## RJM (Apr 11, 2010)

jaydubya said:


> Just out of curiosity, what Kind of material would be needed to use as joists for the 20 foot span with no beam? Would i be correct in assuming that I would need bigger/stronger joists under the part of my house that has a second story than i would under the part with just one floor?


Assuming that there is not a structural wall in the center of your 20 ft span floor, no, you would not need less strong joists under the 1 story part of your house. For a 20 ft span, you're into at least a 2x12, or equivalent, with 16 inch spacing; however, you would really need an architect, or engineer, to look at the specifics (floor loading, finish, wall loads, etc) to provide a real answer.


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## Hamlin (Dec 25, 2005)

Contacting an "engineer" for be sure what is what in your house should be first priority, then check with your local codes to vary exactly what should be used. This varies from state to state and county to county.


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## Jack Wilson (Mar 14, 2010)

Jay post some pictures of your project, I for one am interested in seeing as things progress. Also, they will detail far more descriptively what you are asking questions about.


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## allthunbs (Jun 22, 2008)

RJM60 said:


> You can't notch these engineered beams. The caps (2x4') need to be continuous.


Definitely not. When those things are engineered they take everything into account and you don't want to mess with them. Follow the directions to the letter and if in doubt speak with the manufacturer's engineer. That way, his insurance goes up, not your's.


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## jaydubya (Aug 19, 2010)

RJM60 said:


> Whatever dude. I guess you don't pay property taxes either.


I pay my property taxes to support my community, pay for the schools that My kids attend, and support the fire department that protects my house. I feel that the government dips their hands in my (and everyone's) pockets more than enough. Why should I have to pay a fee to work on my property. I paid for the house. Whats next? a 20 dollar "permit" to do a brake job on my car? a "permit" for my wife to do laundry?? Its a money grab, plain and simple, but thats a subject for another day


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## jaydubya (Aug 19, 2010)

Jack Wilson said:


> Jay post some pictures of your project, I for one am interested in seeing as things progress. Also, they will detail far more descriptively what you are asking questions about.


Perhaps I will try to log it when I do the work. At this point im just not feeling like crawling under the house LOL


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## AxlMyk (Jun 13, 2006)

RJM60 said:


> Whatever dude. I guess you don't pay property taxes either.


Totally uncalled for.


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## Marco (Feb 21, 2009)

Hey Jaydubya..............

I had a similar situation as yours this spring and replaced my floor joists in the Living room. To me, Uncle Jim's input was the best as to fixing your situation

My suggestion is to fix it how the hell you want to since it's your money and your time.

Good luck


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## RJM (Apr 11, 2010)

jaydubya said:


> I pay my property taxes to support my community, pay for the schools that My kids attend, and support the fire department that protects my house. I feel that the government dips their hands in my (and everyone's) pockets more than enough. Why should I have to pay a fee to work on my property. I paid for the house. Whats next? a 20 dollar "permit" to do a brake job on my car? a "permit" for my wife to do laundry?? Its a money grab, plain and simple, but thats a subject for another day


Good points (although I don't agree with them) and you're right, it's an argument for another day but you're the one that posted that you're going to pick and choose what laws you follow. If I was going to break the law, I would have just kept quiet on it.


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## mtnmaniac (Aug 24, 2010)

jaydubya said:


> When i bought my house I didnt have it inspected first (I know.......) and the floors are sagging. At some point the previous owner installed a beam up the middle to resupport the joists. now they are sagging to either side of the beam so I have high spots at the walls and center and low spots between. my floor looks like a big "W". After some detective work i have found that the joists are actually 2x6s that are bowed, notched, doubled, scabbed together, and otherwise compromised in all sorts of stupid ways. i want to replace them altogether. Can anyone tell me what the proper procedure is for this? Due to money reasons I need to do this myself instead of spending big money on a contractor


I haven't read all the following posts to learn more about this situation (I'm finishing up on lunch break), but here's my synopsis on the quoted post:

Initial response is who uses 2x6 for floor joists?!! And next is WHOA! major project! 

Traditionally the entire house needs to be jacked off the foundation walls, the rim joist removed, and then each 2x6 replaced one at a time with proper sized 2x10's onto the sill at each end of the span. Not knowing the span of the room, or what underneath, you need to check with code if there's supposed to be a beam in the center. 

Again, still not knowing the entire situation, the less correct way to ease the problem would be to sister 2x10's along each 2x6. You'll still need to jack the sag out of each section before determing where to position the hangers. Be EXTREMELY carefull jacking and use an extremely substantial piece of lumber or steel do the jacking and any supports. I've seen improperly doubled up 2x4's explode with amazing velocity. Once hanger position is determined, use correct fasteners and devices, and hanger the 2x10's to the foundation walls at each end. Depending on the span, you may or may not need the beam anymore. Local buiding code, and original construction of the building will determine that.

Be very careful and know your limits! This one just may require a professional, or it could get a TON more expensive than you thought you'd save doing yourself. This is a major structural project.

Edit: If underneath is space you don't use, more cross beams would do the trick. Make sure their ends are anchored properly to the walls. Use microlam, it doesn't sag...much... Dimensions depend on span.


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## Cherryville Chuck (Sep 28, 2010)

mtmmaniac is right, it can be a very tricky job that could result in disaster if done wrong. I'm wondering how the house passed a building inspection with 2x6 joists. A very rough rule-rule-of-thumb (and I mean very rough) is that a 2x6 is good for a 6 foot span, a 2x8 is good for an 8 foot span, etc. In practice it is much more complicated. It depends on the species of board and the lumber grade. mtm gave you the most practical suggestion of laminating wider dimension joists to the existing ones, particularly if you could build a pony wall at the outside walls to support the ends. Unless your house is very old, the chances are that the outside walls are sitting on top of the 2x6 joists. Some older houses were "balloon" framed, where the walls were erected and the floor suspended inside them. It might be possible to change the joists here but you still need to be careful. These houses usually had a center bearing wall that held the center of the roof up. I have heard stories of people renovating their houses and removing this wall and having the roof collapse into the house. Bottom Line: if you are not sure- find someone who is to give you advise.


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## jaydubya (Aug 19, 2010)

That part of the house was built in the 50s. Who knows what the codes looked like then


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## Cherryville Chuck (Sep 28, 2010)

Jaydubya,
You say that the current subfloor is 1" T&G. I would check the existing joists to see if they are on 16" centers. With a T&G subfloor it wasn't necessary to be accurate with centers. Any good carpenter would have, but any idiot that would try to cross a 20' span with a 2x6 and only one support was obviously not a good carpenter. If you don't have 16" centers you either have to replace the existing joists to get 16" centers or cut the OSB to odd lengths to match the existing spacing.
I would cut the old joists off as a last resort. If you leave only short stubs they would not be as stable as they are right now. Remember that your outside wall(s) are sitting on this structure. Under normal circumstances that would not be a problem. However, it the house were under stress from extreme winds or earthquake, the short stub/rimplate assembly could fold up, causing the room to shift and possibly collapse.
The best fix is pretty much dependent on the answer to your joist spacing and if it isn't 16" whether you are willing to cut your subflooring to fit odd spacing. When you measure, check to see if you have four foot and eight foot centers too. This is more accurate than going from one joist to the next.


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## amaonline (Jan 1, 2011)

You should check he span tables from the American Forest and Paper Assoc. or the Current International Residential Code book. I can tell you that 10' exceeds 2x6 span capabilities for floor joist even @ 12" o.c.. Is it a one story home and is the floor assembly in question clear span? You should also size your beam(s) or girders according to product span tables.
Save yourself some heart ache and do it right the first time. Span tables are compiled by engineers and are worth the time and effort to look into.


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## Marco (Feb 21, 2009)

OK Jason. How did the Floor Joist replacement go and how did you end up replacing them?


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## Elevenz (Mar 19, 2011)

Find the Holmes on Homes episode recently shown where the joists were replaced.


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