Sistering joists for 8 x 5 bathroom
Tearing out a bath and wanted to get some opinions on sistering the joists.
The house is circa 1929 and the bath is 8 x 5 on the first floor. I have some access from below via the closet that holds the sump pump, roughly 4 feet out from the exterior wall.
Existing joists are 1 5/8″ x 9.5″ x 12.5 feet long, and 16″ on center. Supported by steel I beam in the middle of the basement.
Wanted to make sure I had the process correct…using urathane glue, clamp a 2 x 10 to the existing joist, then nail the new joist to the old (nailing every 8″ — 5 nail pattern at the ends, 3 nail pattern in between). Or would screwing them together with something like McFeely’s promax be better? There are 5 joists running through the room, and I can access 8 feet of them (from the exterior wall in), without trying to remove the basement ceiling. Is this enough of a span?
Now, the real question…where the exisiting toilet is, the plumber cut one joist right off — about 2 feet from the exterior wall — for the flange. (see photo1, photo2) Can I create a header out of the joists like this (green = existing joists / black = proposed fix) and use joist hangers to tie them together? Should I use a double plate there? It appears that was the idea behind what’s currently there, except there are no joist hangers, or extensions coming from the exterior wall. (It’s just sort-of nailed there, and poorly done, to boot) There are also some notches on other joists that are pretty deep (first joist along wall with vent for sump pump?) and (joist where existing tub was located) Yeah, I know it’s a mess.
The existing plumbing is all being torn out this weekend (probably not that vent for the sump pump, though). The new plan is to switch out the toilet and tub locations, putting in a restored 5′ claw foot tub parallel and close to the exterior wall (and perpendicular to the joists). New floor will be 4″ octagonal tile, so I don’t think I’m running into any deflection issues, yes?
Thanks for your thoughts.
Steve
Replies
Greetings Steve,
This post, in response to your question, will bump the thread through the 'recent discussion' listing again.
Perhaps it will catch someone's attention that can help you with advice.
Cheers
Andrew Clifford of Clifford Renovations, who serves as a steward of our history for future generations
We can imagine something that only exists in our heads, in a form that has no measureable, tangible reality, and make it actually occur in the real world. Where there was nothing, now there is something.
Forrest - makin' magic every day
I'm no expert, but the only time that I've done this I used bolts to hold the joists together near the ends. It may be over-engineering, but I was sure that they wouldn't come apart. I then did the glue and nail part.
Use nails, not the screws. Hardened screws (even stainless) should never be used in a structural application. They can flex with the structure, so they will break suddenly when overloaded - not a good thing. Unless I'm mistaken (someone correct me if I am), the McFeelys are made for attaching decking to joists, not structural use. If one breaks you get a loose board, not a failed structure.
I did a similar plumber hack repair recently - I used the joist hangers in a similar way to what your thinking of without any problems. Make sure you add a doubler to every notched joist, unless it is a really shallow notch (someone posted a table showing allowable notches recently, but I don't remember what the string was).
Make sure the doubler is tight to the old joist before sinking the nails. I've also used lag bolts or cartridge bolts/nuts to do the same thing - it helps because they draw the two 2xs together, so I didn't have to clamp them together first, but otherwise is more work without adding any strength.
Thanks FlashGordon,
I did see that chart on acceptable hole sizes earlier. And at least one of the notches is well beyond the acceptable limit, so that will get some assistance.
Thanks for the clarification on nails v. screws. Makes sense.
Steve
Steve,
Typically the nerdy engineers would want you to extend the new joist all the way to the exterior wall. I guess a lot of it depends on what you're trying to accomplish. If you want to stiffen the floor up than extending the new 2x10's the eight feet will help - how much it helps is hard to say. If they bridge the notches than that should help greatly. Adding the header and doubling up the existing joists taking the load of the header is a good idea.
Is the floor bouncy? I'm trying to understand the need for the reinforcing because the existing joists aren't spanning too far for the size that they are.
I also always specify two or three rows of 16d nails @ 12" o.c. for typical joist reinforcing.
J
Thanks J,
No, the floor isn't bouncy. At least not that I've noticed in that room (or anywhere else in the house). The wood floors elsewhere on that 1st level are squeaky in spots; but I think that's more from a pretty old subfloor, as opposed to bouncy joists.
As for the reason behind the sistering...it's on the advice of the plumber I had in to price out roughing in the new lines. The one joist that is severed obviously needs to be repaired. There was a crack all the way up to the tile right next to the toilet flange. After pulling the mud bed up I can see why it happened.
What's your opinion on glueing the sisters together before nailing? Is that beneficial?
I can and plan to extend the sister all the way along to the exterior wall. That's all within the open space.
Thanks,
Steve
Steve,
Glueing always helps bond everything together - as a structural benefit, I never take glue into consideration. I would say don't worry about glueing it together - it'll save a little cash and some extra time and mess.
I know the hole and notch table is in the code in the floor section if you have one of those handy. For a 9 1/2" deep joist the allowable depth of the notch is d/6 or 1.58". The length of the notch would be d/3 or 3.16" and those can't be in the middle third of the joist.
J