# Adding A Joist To A True 2x6, Floor System



## Agility (Nov 29, 2013)

I've done a fair amount of old house restoration but I guess I've always gotten lucky when it comes it comes to using the existing joists to carry my new subfloor (then the original subfloor gets pulled, milled, and finished as flooring). 

In my own "new" house, built in 1875, I need to add a joist in the living room before I can put down Advantech. The other option is pulling down the bathroom wall and replacing subfloor in two rooms at once...but it's our only bathroom for the next year or two.

I have old, true 2"x6" joists spanning 12' on the first floor and 14' on the second floor. I'll need to rob all the original subfloor in the house in order have enough material to lay restored original material throughout the home. One obvious benefit to replacing all this original subfloor is that I'll be able to stiffen things up and eliminate a fair number of old house squeaks as I go. 

I'm hoping for a graceful solution, like an engineered 6" product. It's an old house so I'm not worried about deflection, I just don't want to throw an oversized joist in that bay and never be able to rock the basement lid. 

Who's done this before? Any ideas?


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## griz (Nov 26, 2009)

Rip a 2x8 to dimension.


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## VinylHanger (Jul 14, 2011)

Or just throw a modern 2x in there and fir it down in the future. Pretty simple stuff.


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## Agility (Nov 29, 2013)

griz said:


> Rip a 2x8 to dimension.



That simple, huh? Am I just over thinking it?

If I had to replace like 5 or 6 joists in a row (I don't) would that still be the advice? A KD 2x8 ripped to 6" to span 12' or 14' would be significantly bouncier than my existing true 2x6s, no?


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## Agility (Nov 29, 2013)

VinylHanger said:


> Or just throw a modern 2x in there and fir it down in the future. Pretty simple stuff.



Not enough headroom to spare, unfortunately. In the basement, which was added in the 80's, I have 6'8" from floor to bottom of joist currently. 

If I dropped the ceiling more than an inch my brother wouldn't be able to stand up in my eventual man cave when he comes to visit.


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## jlyons (Apr 17, 2011)

I put 2x8's in mine sistered to the original 2x6 and also used the extra height to level things out as well as stiffen things up.


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## Tinstaafl (Jan 6, 2008)

Agility said:


> If I had to replace like 5 or 6 joists in a row (I don't) would that still be the advice? A KD 2x8 ripped to 6" to span 12' or 14' would be significantly bouncier than my existing true 2x6s, no?


So double 'em up and they'll be significantly less bouncy.


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## hdavis (Feb 14, 2012)

If you're just sistering on one, use a modern 2X6. If you're putting one in stand alone, use a modern 2X6 and shim under it to get the right height. Alternately, you can put it in and shim over it, but it's more work.

Without seeing your exact situation, the reason why ripping a 2X8 to exact width may not work is you may not be able to sledge it into place. Using the 5 1/2" modern one gives you clearance to get it positioned exactly where you need it without jacking, sledging, hammering, or prying.


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## hdavis (Feb 14, 2012)

Replacing one joist, and you have basement access?

1875, so this was balloon framed. The end of the joist at the foundation level was usually set into a pocket on the outside wall, and over a beam on the inside. To get the stiffness, you'll need to double modern 2X6s. The end will have to slide over the beam, then into the outside pocket, but these aren't full depth if they're into a wood sill. You'll have to use a hanger as well, if that's how it is. Shim under both ends.


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## TimelessQuality (Sep 23, 2007)

Tinstaafl said:


> So double 'em up and they'll be significantly less bouncy.


And block it tight


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## griz (Nov 26, 2009)

For your situation a Flitch Beam out of 2x6 will work well.

I've done them using 1/2" plywood and glue & screw/bolt the whole thing.


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## EricBrancard (Jun 8, 2012)

Why not order some true 2x6 joists to match the existing?


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## VinylHanger (Jul 14, 2011)

Agility said:


> That simple, huh? Am I just over thinking it?


No worries. My middle name is overthinking.


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## Tom M (Jan 3, 2007)

Natural/modern 2x is good, LVL will be better with no shrinkage. I have also beefed up over spans by gluing 3/4 cdx on each side of the center of beams.

I work with an architect in the past that would suggest propping up floor framing to create a camber/crown then block and glue with a heavy sub floor. Once dried and independent it was like a rock.


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## Agility (Nov 29, 2013)

VinylHanger said:


> No worries. My middle name is overthinking.


I guess I was expecting "yeah, you need a Flimflam joist from the Whatever company, they're expensive but luckily you only need one."

I'll be doubling ripped 2x8s and blocking.


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## Agility (Nov 29, 2013)

hdavis said:


> Replacing one joist, and you have basement access?
> 
> 
> 
> 1875, so this was balloon framed. The end of the joist at the foundation level was usually set into a pocket on the outside wall, and over a beam on the inside. To get the stiffness, you'll need to double modern 2X6s. The end will have to slide over the beam, then into the outside pocket, but these aren't full depth if they're into a wood sill. You'll have to use a hanger as well, if that's how it is. Shim under both ends.



You just about hit the nail on the head. But my joists are in pockets on the outside wall and the interior beam.

And also I'm adding a joist, not replacing one. I need somewhere for my subfloor to land, otherwise I'd have to start gutting another room. Hoping to go one room and a time.


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## Tom M (Jan 3, 2007)

You can notch 1/4 the depth on the bearing ends. Can you combine the lumber difference of the old wood with a notched 2x8? Not ripped....set it up where the advantech runs over the T&G sub floor coming from the bath side. Make a threshold at the door.

Special ordering a dozen true 2x6 like the original is not a bad idea at all either. Blocking and glue will be needed to make up the lost strength of the original T&G fir. I assume thats is what you have.


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## hdavis (Feb 14, 2012)

Agility said:


> You just about hit the nail on the head. But my joists are in pockets on the outside wall and the interior beam.
> 
> And also I'm adding a joist, not replacing one. I need somewhere for my subfloor to land, otherwise I'd have to start gutting another room. Hoping to go one room and a time.


Then just a double modern, with a couple hangers?


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## digiconsoo (Apr 23, 2012)

Agility said:


> I'm hoping for a graceful solution, like an engineered 6" product.
> 
> Who's done this before? Any ideas?


Like griz said, flitch, using ply or steel.

Steel flitch plate assemblies with tight blocking really make nice solid floor framing in older homes with overspanned lumber - I've used that solution a few times.

You can make your own, or order premade as in this article:
They're using it in a flush beam situation, but same principle.

http://homeremodelersstore.com/web_articles/framing/install flush beam.pdf


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## Agility (Nov 29, 2013)

hdavis said:


> Then just a double modern, with a couple hangers?



Slight change in plans. I pulled the carpet and the 80's wood flooring it was laid on and found that on the offending side of the room the particle board was laid on shims on the original subfloor. Tall shims. 

Here is a cross section of the adjacent room, taken from the basement staircase. I cut it out when I realized what was going on. 









From bottom to top: true 2x6, original subfloor, ripped modern 2x shim, particle board subfloor, drywall. 

I think this place got a gut-remodel in the 80s when it was lifted and given a basement. It's not on the permit for the basement though, it's just what my neighbor said.


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