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Discussion Starter · #1 ·
I am working on correcting several things at once as I prepare to remodel my bathroom, including a complete DWV rework. Part of the remodel is laying porcelain tile. In order to do so, I need to strengthen the floor a little bit. House was built in 1943 and I'd love to be able to say it is 16" OC, but best I can do is that SOME are 16 OC, and some are 9, and some are 12..well, you get the picture. For some reason around the bathroom area where I am working, the spacing isn't consistent and it appears to be due to perhaps previous (bad) attempts at strengthening and reducing deflection, etc. That being said, it still needs to be corrected just a little bit.

I will sister 2 joists (by the way, verdict is out - adhesive between sistered joists necessary or not?) I will also split the difference between 2 joists that are 16" OC right at the point where the tub shower combo will be and a point of lots of stepping over the years.

Joists are 2 x 8, 11.5' by the way. My joists are currently all cross braced with 1 x 3 wood bracing and at least that part was done well, though when whomever did what they did around the bathroom kitchen area, they removed them but didn't replace.

So, I can't really use the metal bracing as I am not standard length, plus I am not sold on whether or not they do a decent job really. I don't want to block because, of course, I have lots of plumbing and electrical in this area and that would be more trouble that it is worth; However, I can do 1x3 bracing except I can't quite figure out the best way to attach the bracing to the joists since the flooring is already in place, of course.

So, what are some options to get the top of the bracing (at the subfloor) attached properly and with as minimal cussing as possible. Thanks!
 

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Naildriver
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Bracing helps keep the joisting from twisting. Since it was built, it has twisted all it will. Make sure your plumber(s) haven't cut joists to install toilets, and things like that. Adhering sisters is a good idea along with structural screws, not drywall or brittle ones. Are you adding subflooring layer to what you have? Incidentally, what do you have for a subflooring? Thickness. 2x8's can span 11 1/2', but it depends on their age, condition and by sistering them, you are adding to that strength.
 

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Discussion Starter · #3 ·
Thanks for the reply. I get that the bridging assists in stopping twisting and that is fine however, I am adding in a new joist that will not be sistered, so I will be bridging that one for that exact reason as well as the added load displacment that comes along with it. The floor is still above in this instance. That being said, your question about subfloor did get me thinking..I will actually be replacing most of the subfloor with a 3/4" plywood as well as a new 1/2" underlayment. I think I can do most of the bridging after o pull the subfloor up. That will make those easier for sure. However, there will still be a few areas on a couple of the joists where I'll have to bridge where the floor won't be removed as it isn't in the bathroom.

There is no way to fasten the top of the bridge at a downward angle into the top face, can I go from the back of the joist the bridge is attached to at an upward toenail into the bottom face of the bridge board? Honestly seems like I don't really have a choice really.
 

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Naildriver
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The theory is that the joist is held firmly by the subflooring. Applying the 2x4 to the bottom negates twisting, and as Neal said, either position is fine.
 

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That's because a panel of flat steel costs more than crossed bars. Also, a flat panel isn't as aerodynamic as bars. You don't need to worry about aero for your joists, and if blocking instead of X-bracing breaks your budget, well...
 

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retired framer
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We install bridging from above and there are lots of places with odd sizes and they get a 2x6 block or what is handy from above. After plumbers and HVAC guys get done taking out the bridging and blocks, we go back and just put flat 2x4s from below. evenly spaced no more than 7 ft from support or each other.
 

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Old building codes required all joists to be blocked or braced every 8 feet, but that requirement is no longer in place for 2x8 joists* because the subfloor by itself prevents the joists from rotating (not twisting) under loads. (Joists still need to be blocked at their supports.) That means that you don't need to bother replacing the missing old braces or adding new ones.
* d/b for 2x8 joists = 7.5/1.5 = 5. See NDS 4.4.1.2
 

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Hammered Thumb
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* d/b for 2x8 joists = 7.5/1.5 = 5. See NDS 4.4.1.2

That means that you don't need to bother replacing the missing old braces or adding new ones.
Bridging (either solid, wood/metal cross, or continuous 1x3 across bottom) is not code-required for a joist smaller than a 2x12 given proper attachment of the subfloor. The IRC is what is adopted most anywhere, so inspectors will not consult AWC's depth/breadth ratios to determine bridging, but they would probably ask for it on a 2x10 just as habit.

However, bridging is still installed by most, especially when remodeling older houses where the subfloor has been hacked over the years and may not have been fastened correctly originally. It will stiffen a floor, and solid blocking can spread the load out more and lower deflection, even if by just a hair. So it is good practice to install/replace it, especially when having tiled floors.
 

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Discussion Starter · #17 ·
However, bridging is still installed by most, especially when remodeling older houses where the subfloor has been hacked over the years and may not have been fastened correctly originally. It will stiffen a floor, and solid blocking can spread the load out more and lower deflection, even if by just a hair. So it is good practice to install/replace it, especially when having tiled floors.
This is exactly why I am adding it. I wasn't worried about code as I knew it wasn't required. The floor is a little spongy, but not bad, but I am also adding porcelain tile to the floor above where it didn't exist previously. I am remodeling to sell, and surely don't want anything to crack before I sell it. It's a fairly simple addition that has pretty decent return on results so I might as well.
 
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