Water damage repair question for the building pros

I'm buying a project house. There's a toilet that had been leaky for a bit. It rotted out the surrounding subfloor and softened a joist too:

I'm good with sistering a length of joist next to the damaged joist, but I'd also like to make sure that the toilet flange isn't sitting directly on top of soft, rotted wood. Any reason why I couldn't section out the soft wood, and drop in some good stuff? I'm thinking I could remove a section about the size of a 2X4, insert the appropriate filler, and then secure the "patch" to the original joist?

Cut out along the blue line basically and replace with new wood?

Any suggestions for hardware/plates to secure the "patched" section to the original joist?

Not a professional but my house was built in 1894. =~ 0

You could cut & paste a piece as shown, use pressure treated.  But then sister another 2 X 6 right up against the rotted one; then box the flange with  2X6s perpendicular to the joist at the top of the page.  With 2X6s (or any other load bearer) it's the top and bottom of the board that carries the load.

Did the toilet flange not sit on top of the old subfloor and flooring? If not, that's probably why it leaked. Without support, it was moving. The subfloor was moving around the flange and it was too low. All things a wax ring hates. 

Sister out the joist, replace the rotten wood, and support the flange so it can't move separately from the floor. 

Edit to add this. 

Edit again to say: I'm not a pro, but I have had to replace a bathroom floor or two because of flanges being set wrong. 

Toyman! said:

Did the toilet flange not sit on top of the old subfloor and flooring? If not, that's probably why it leaked. Without support, it was moving. The subfloor was moving around the flange and it was too low. All things a wax ring hates. 

Sister out the joist, replace the rotten wood, and support the flange so it can't move separately from the floor. 

 

Edit to add this. 

Edit again to say: I'm not a pro, but I have had to replace a bathroom floor or two because of flanges being set wrong. 

This, plus reframe(2x6) around the commode flange .....

In reply to Toyman! :

I think the subfloor did support the flange, at least until it got soft. But it sure looks like the flange is resting directly on that joist in the pic. I'll have to check more closely when I've got a chance.

The subfloor in that area had obviously been replaced at least once before. I'll make sure that it's done right when I close it back up. Just wanted to make sure that I wasn't asking for trouble by cutting out the soft part of the joist and putting more solid wood back in. And I was also hoping for some suggestions for methods of securing the new solid wood to the joist that won't make people groan if they ever open it back up.

STM317 said:

In reply to Toyman! :

I think the subfloor did support the flange, at least until it got soft. But it sure looks like the flange is resting directly on that joist in the pic. I'll have to check more closely when I've got a chance.

The subfloor in that area had obviously been replaced at least once before. I'll make sure that it's done right when I close it back up. Just wanted to make sure that I wasn't asking for trouble by cutting out the soft part of the joist and putting more solid wood back in. And I was also hoping for some suggestions for methods of securing the new solid wood to the joist that won't make people groan if they ever open it back up.

Big nails and some liquid nails with plenty of both.

What size are the floor joists? That rotted one doesn't look all that bad and I would leave it alone after disinfecting it. Do add another joist to that existing joist with as much overlap as you can fit (4' on each side of the sewer line would be nice).  Use lots of 2.5" screws. Add 2x4 nailers to the surrounding joists where your new plywood underlayment will screw off including perpendicular to the joists. Use PL400 construction adhesive liberally along with treated plywood.

Screws and glue is what I use. I hate a squeaky floor. I also used treated plywood in my last replacement. If you go that route, get the driest piece you can find and use lots of screws. You don't want it to move as it dries the rest of the way.

Do you own a nail gun? do not support off the plywood flooring if you can....

VolvoHeretic said:

What size are the floor joists? That rotted one doesn't look all that bad and I would leave it alone after disinfecting it. Do add another joist to that existing joist with as much overlap as you can fit (4' on each side of the sewer line would be nice).  Use lots of 2.5" screws. Add 2x4 nailers to the surrounding joists where your new plywood underlayment will screw off including perpendicular to the joists. Use PL400 construction adhesive liberally along with treated plywood.

It's a 2X10 joist, so lots of material. I'm not super concerned about loss of structure in the joist, but I do want to make sure that the subfloor has a flat, strong surface to screw into.

I realized that I've got some 3", 5" and 6" StrongTie lag screws on the shelf that I might as well use.

I'm thinking that I'll predrill the patch piece from the top, and run them down into the joist from above. Then plate one side and screw through the scissored joist as well. I've also got some 2x4, and 2x8 scraps from some crawlspace framing work laying around that I can use for nailers if I'm feeling frisky. Subfloor will be screwed down well.

Since this seems to have been necro-bumped I guess I can add a pic of the repair. Ignore the gross plumbing and insulation. It was redone shortly after the framing was fixed.

I cut out a roughly 2X4 section from the top of the rotted joist (outlined in blue earlier in the thread) and secured it with 5" Simpson bolts vertically. I added framing between the joists to better support the toilet flange. And I sistered a new joist to the original/repaired one. Hopefully it will do a much better job for a much longer time than the last setup!

Nice repair. That looks super solid now.

Don't you want that flange at least on top of the sub floor, if not the finished floor?

NermalSnert (Forum Supporter) said:

Don't you want that flange at least on top of the sub floor, if not the finished floor?

Yeah. The flange in the most recent pic was actually cut off and just sitting there so I could properly space the framing. It's all new plumbing, with proper flange height, fully supported by the subfloor now.

Now add flat 2x4s at every non supported cut of your sub-floor. Use 2" construction screws @ 4" o.c. and lots of PL 400 construction adhesive. You are just trying to connect the pieces of plywood together which would normally be supported over a joist along the plywood butt joint short side or the plywood tongue and groove long side.

In reply to VolvoHeretic :

Yessir. That was done on any seam that didn't land on a joist (although I skipped the glue).

STM317 said:

In reply to VolvoHeretic :

Yessir. That was done on any seam that didn't land on a joist (although I skipped the glue).

To be fair, that only really applies if you have the World's Greatest 
$1,500 Stereo that can extract nails 10' away from the speakers.  (I also recommend that everybody put friction fit fiber glass insulation in ALL interior walls.)