(Massively?) Bored Joists need re-inforcing
Sorry for re-posting ... in hindsight, I felt this topic was distinct from "bouncy floors"
I was forced into renovating a second floor bathroom for numerous reasons. Never having liked the layout, I thought this was a perfect time to change it.
The room is 70" wide by 126" deep. I wanted to put the vanity on the left wall, the toilet next to the vanity and then the tub on the back wall, drain to the left, so the left wall would become a wet wall.
Problem was, the joists ran across the room, not down. Putting the toilet on the left wall would force me to bore 4" holes through 2"x8" joists. The two joists to be bored would sit directly under the tub. A real no-no.
I did a little (clearly, not enough) research on the internet & mostly talked to some local building supply stores. I had an idea that laminating (glued & screwed) 7 1/2" X 30" strips of 3/4" plywood to both sides of the joists might provide enough support that the joists could then be bored.
And this is where I was ill-advised. I was assured this would provide enough support, and that with 3/4" ply subfloor followed by 1/2" cement board the floor would be solid enough to support the tile I wanted to install.
After completing this portion of the renovation and replacing the subfloor, another trusted advisor spoke up and said that I can't do that. I've since stopped the renovation in order to take the time to figure out what to do so that the plumbing and floor support will be safe and to code; hence, my now having found this thread.
As an FYI, in doing my second round of research, I stumbled across these metal joist reinforcers - http://www.metwood.com/products/reinforcer . They look like just the thing I need to solve my support issues, assuming I leave the bathroom in it's current configuration. The problem with them for me is that they cradle the bottom of the joist and I don't want to have to tear up the first floor ceiling in order to install them.
So, one of my questions for all you engineering gurus with your mathematical wizardry is, if I were to attach 30" long strips of 1/8" or 3/16" steel strap to both sides of the joists, both above and below the holes, do you think this would provide enough support for a full tub of water and a tile floor?
If so, how would you suggest fastening them? Should they be screwed independently to each side, or bolted so that they sandwich the existing laminated joists? Further, should I be using some form of glue or cement to 'laminate' the strapping to the bulked up joists (not that I'm aware of any metal-to-wood adhesive)?
Another option I have is to remove one side of the plywood lamination I've done. Then sister both existing joists with a new (at least 6', but as long as possible) joist that has one of the joist reinforcers listed above attached. Due to the construction, the joists are fully supported by a bearing wall on the left side of the washroom so these new sistered joists would have the benefit of being supported on one end.
Any thoughts on any of these potential solutions?
Thanks in advance for anything shared.