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Old 01-30-2009, 11:20 PM   #16
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Help! Sagging Floor Joists-Second Story>>>Undersized!!!


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I just bought my first home that is a 1 1/2 story Bungalow-style farmhouse built in 1919. I am in the process of remodeling and am currently redoing the ceilings in the dinning room and living room. Upon removing the old plaster and lath boards, I confirmed what I already knew from the upstairs...my upper story floor joist are sagging. The joist are 2x6(I believe they are oak) and span approx. 16 ft. in the living room and 14 ft. in the dinning room. Some joist have have holes drilled in them where the wiring was ran and there are a couple that are cracked a little.
Something that people are not taking into consideration is the fact that these joists are oak (if in fact they are) and they are probably true 2" x 6". It that is the case this would change the load carrying capacity of these joists.

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Old 01-31-2009, 12:38 AM   #17
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Help! Sagging Floor Joists-Second Story>>>Undersized!!!


An architect answered a posting a while back on someone asking if the could strengthen their floor joists by running particle board down each side of the joists under his floor.


The architect said the he couldn't use particle board because it's glued together and doesn't have a single direction that the grain runs in. He gave the formula that architects use for the “anti-sag” calculations.


The formula I remember to be something like the wider board minus the thinner board to the third power, but I know that isn't the correct one. I calculated the difference between a 2x4 and a 2x6 when I saw the calculation and it ended up 9.?? close to 10 times the “anti-sag”. The architect had a times something which equaled E (which was the “anti-sag”). The difference between what I recall was a 2x10 and a 2x12 was as I recall 177% increase. The increase between a 2x4 and a 2x6 was a much greater value that the difference between a 2x10 and a 2x12. I searched for the posting, but couldn't find it.


The architect told him that running a 1 bye of real wood because of the grain down each side would give him the additional strength he was looking for.


The guy that made the posting did not have a sagging floor he wanted to prevent it.


The architect told him for the maximum strength to glue the sisters and put a lot of nails in to hold the sisters good an tight while the glue sets.
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Old 02-02-2010, 03:46 PM   #18
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Help! Sagging Floor Joists-Second Story>>>Undersized!!!


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Originally Posted by Danton84 View Post
I just bought my first home that is a 1 1/2 story Bungalow-style farmhouse built in 1919. I am in the process of remodeling and am currently redoing the ceilings in the dinning room and living room. Upon removing the old plaster and lath boards, I confirmed what I already knew from the upstairs...my upper story floor joist are sagging. The joist are 2x6(I believe they are oak) and span approx. 16 ft. in the living room and 14 ft. in the dinning room. Some joist have have holes drilled in them where the wiring was ran and there are a couple that are cracked a little
Something that people are not taking into consideration is the fact that these joists are oak (if in fact they are) and they are probably true 2" x 6". It that is the case this would change the load carrying capacity of these joists.
I really wish there was a span table for a true 2x6 made from old oak that is much harder than anything you'll ever find today.
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Old 02-02-2010, 04:11 PM   #19
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Help! Sagging Floor Joists-Second Story>>>Undersized!!!


that's a tough problem Danton84. Makes me glad my floor joists are 2x12 in my 1964 built house. Let us know what you decide, and take pictures of the work.
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Old 02-02-2010, 04:45 PM   #20
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Help! Sagging Floor Joists-Second Story>>>Undersized!!!


Back in 1919 2x6 is probably a true 2" x 6" and oak they probably are stronger than 2x6 of today.

So even if the floor sags a bit it don't squeak and seems strong if I was concerned about the sag and wanted a level floor I probably would level it from the upstairs.
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Old 02-02-2010, 07:48 PM   #21
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Help! Sagging Floor Joists-Second Story>>>Undersized!!!


I ran into the same situation last summer when I was remodeling our 1920s bungalow. I did a combination of all of the suggestions above. I ended up cutting in a double LVL header under my attic knee wall. Existing 2x6s supporting the attic floor behind the knee wall were sistered with 2x8s as shown. In the living area, I ripped out the sagging 2x6s and replaced with 2x8s. It's the only way I could guarantee it would come out level. See the attached photo for a general idea.

I had thought about living with the sag, but now that the project is done I'm very glad I took care of it.
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Old 02-02-2010, 08:31 PM   #22
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I ran into the same situation last summer when I was remodeling our 1920s bungalow. I did a combination of all of the suggestions above. I ended up cutting in a double LVL header under my attic knee wall. Existing 2x6s supporting the attic floor behind the knee wall were sistered with 2x8s as shown. In the living area, I ripped out the sagging 2x6s and replaced with 2x8s. It's the only way I could guarantee it would come out level. See the attached photo for a general idea.

I had thought about living with the sag, but now that the project is done I'm very glad I took care of it.
Why did you run them the "long" way instead of the shorter distance across the room?
Or is that a multi-2x beam in the middle that the 2x8's are hanging on ?
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Old 02-02-2010, 08:44 PM   #23
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A note about repairing sag - any methods that involve jacking up the floor (sistering, bracing, etc etc)

If your floors have sagged for quite some time that means your flooring on top of the sag has also relaxed down into the sag (it's warped, crowed, etc, to fit the dip). For some flooring it doesn't matter (carpet, laminates for example - they are flexible)
But others that are solid or less flexible might have problems when you go to fix them:
If it's hardwood - the slats have taken a new shape they might not "relax" when you fix the floor.
Any repair jobs that previous owners have done to the floor might be "popped" loose when you jack up the floor - you'll have to fix it.
Tilework and bricks might crack. . . etc.

In my kitchen the floor sagged considerably - we had to sister in new beams to fix it. In the process of jacking up the floor to install the new beams the sagged portion of underlayment was no longer held down with pressure like: \__/ - so nails started to pop up, they eventually popped through the flooring in the room. . . and eventually the top underlayment separated from the bottom underlayment and the floor "jumped" up - so there was a crack in the floor.

I had to remove the old flooring, level it off and readhere the underlayment (I used screws to pull the separated sheets together) and so forht - it took extra time and work but eventually I got the floor evened out. It's not perfect, you can still feel a rise where the sag use to be de to the previous owners repairing the area with too thick of underlayment - but it'll be ok until I rip it all up.

So - if you have a sag just be aware that other problems might come around after you fix it. But after the effort to fix the sag these little problems might seem like small beans.

Further note - if it sags because your beams are undersized then *yes* fix it - don't just leave it alone. A little sag due to settling is one thing but sag due to undersized beams can put too much pressure on the beams - eventually causing them to break. I've had to sister countless beams under my entire house because sag lead to breakage.

If it's lasted for 90 years, you're lucky - but I wouldn't bet on it going for another 90.
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Last edited by Snav; 02-02-2010 at 08:47 PM.
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Old 02-02-2010, 08:53 PM   #24
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Why did you run them the "long" way instead of the shorter distance across the room?
Or is that a multi-2x beam in the middle that the 2x8's are hanging on ?
Mainly so I could sister the 2x8s onto the existing 2x6s left behind. Also - the wall on the right wasn't originally load bearing. I had to add the doug fir 4x4 in the wall to take the load from the double LVL directly to the timber beam in my basement.
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Old 02-02-2010, 08:55 PM   #25
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ll you need to do is ask! And some math....... Table #7, page 643: http://books.google.com/books?id=DWs...olumns&f=false

Flitch plates: page 655--------------then the spans and math per inch, starting on page 717. Three kinds of oak, page 651.

Are we having fun yet? Lets put 50 men in one room,elbow room only, to test the floor: you find it.

Be safe, Gary
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Old 02-02-2010, 08:55 PM   #26
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Stubborn, That makes sense - if you ran them the other way the wall on the right with the 4x4 would then be pulling the load for the entire overhead - which would have made more load for you to direct to the basement beam.
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Old 02-02-2010, 09:00 PM   #27
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Mainly so I could sister the 2x8s onto the existing 2x6s left behind. Also - the wall on the right wasn't originally load bearing. I had to add the doug fir 4x4 in the wall to take the load from the double LVL directly to the timber beam in my basement.
I see it now, I thought they might be LVL's in the middle
Also missed the sistered joist on the back side
If I ever rip the ceiling down in my main room I'll be sistering 2x8's to the existing 2x6's too
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Old 02-03-2010, 06:35 AM   #28
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Originally Posted by stubborn1 View Post
I ran into the same situation last summer when I was remodeling our 1920s bungalow. I did a combination of all of the suggestions above. I ended up cutting in a double LVL header under my attic knee wall. Existing 2x6s supporting the attic floor behind the knee wall were sistered with 2x8s as shown. In the living area, I ripped out the sagging 2x6s and replaced with 2x8s. It's the only way I could guarantee it would come out level. See the attached photo for a general idea.

I had thought about living with the sag, but now that the project is done I'm very glad I took care of it.
"NICE WORK"
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Old 02-03-2010, 10:58 AM   #29
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Help! Sagging Floor Joists-Second Story>>>Undersized!!!


I have an old house also (1925 American Four Square) with 2x8 floor joists throughout. In the 2nd floor Master bedroom, the floor joists span 16 ft. and it sags in the middle. I was told by a few General Contractors that that's the way it is and it is not critical to replace since the wood used is much stronger than todays pine. I agree, when I try to nail or drill into a joist in the basement. It is very hard.

However, I did add 2x8 blocking in the middle of each joist in the basement for the 1st floor. The blocking seemed to help with the bounce but not the sag.
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Old 02-03-2010, 02:47 PM   #30
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Help! Sagging Floor Joists-Second Story>>>Undersized!!!


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I have an old house also (1925 American Four Square) with 2x8 floor joists throughout. In the 2nd floor Master bedroom, the floor joists span 16 ft. and it sags in the middle. I was told by a few General Contractors that that's the way it is and it is not critical to replace since the wood used is much stronger than todays pine. I agree, when I try to nail or drill into a joist in the basement. It is very hard.

However, I did add 2x8 blocking in the middle of each joist in the basement for the 1st floor. The blocking seemed to help with the bounce but not the sag.
I have 1907 2x6s 24-32" OC that span 14ft in one room, and 16ft in the other (they also used 2x6s for the floor joists, and amazingly they do not bounce worth a damn). The 14ft span bounces, and the 16ft doesn't. Go figure. I did find the culprit joists and need to sister them sometime (one joist is bowing from the side, the other seems to have water damage of some sort). I was also thinking of bridging the joists with solid 2x6 (although they're be smaller than the true 2x6 used back then). Glad to know that newer wood is able to help out older wood.

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