I'm replacing some rotted subfloor around a toilet, and I want to add blocking around the flange for extra support, and to give me a place to support the new pieces of subfloor (I'm not planning on replacing the flange). What complicates things is a pipe running parallel to the joists just an inch or so beneath the subfloor.
Picture:
My thought was to first fill out the joist webbing (yellow) and then build a box (white) to surround the plumbing (red). The horizontal beams perpendicular to the joists could only be as thick as the joist flange due to the upper pipe.
Would this approach provide decent support for the replacement floor and the toilet? If so, what kind of materials would be ideal to use?
Best Answer
For Future Viewers:
Right idea, but WAY too complicated for minimal support & no screwing for the flange. With NO FLANGE in place, build a frame first, not piece by piece in the floor. With a Flange in place you'd build it without the right side's {bottom} joist attachment so you can dry-fit everything & finish inner attachments to then LASTLY screw to the joists.
Stand up 2x4's to be attached to joists LAST. Then, bridge the Stand-Ups with 2x4's On-Flat. You screw through the Stand-Ups & into the ends of the On-Flats (do just the left Stand-Up {top} configuration if a Flange is in place).
Then, you bridge the On-Flats with a shorter On-Flat. First, screw that in from the left Stand-Up to hold it in place & toe-nail screws on either end at the Flange side. Also, toe nail what can fit On-Flat on the right side {bottom} of the Flange Finish by just screwing outward (& angled upward for this Askers I-beam pictures) through the Stand-Ups & into the joists.
This should be snug to the Flange's underside collar or the drain pipe, depending on your subfloor elevation. The On-Flats even allow you to cut or drill the platform frame for an actual tight fit complete circle. Of course, adjust this proven design to your actual application.