Replacing tub and surround, I removed vinyl floor to find plywood tongue and groove decking with water damage. Cut out the damage to learn that the construction plumbers had cut the 2x4 top of floor joist (TRUSS BUILT WITH TOP AND BOTTOM 2X4 AND CLEATED BRIDGING.) to accomodate the p-trap for the tub drain. They did not add any supports and over the years the bathroom floor has sagged approx 1-1/4 inches between the two unaffected joists (48 inches). I installed a section of 2 inch x 3/8 inch angle iron and fashioned a jack using a 1 inch threaded stud and nuts to work like a house jack. Seemed like a good fix, except the cleats started to come out of the plate, and then the ceiling of the room below had drywall tape pop out along with a few sheetrock nails. I also did not get the bathroom floor level enough to properly install the tub and new ceramic floors. That particular floor joist spans the width of the townhouse and does not have mid point support. The adjacent joists are level and secure, thus causing a valley between two peaks. Is there a better way to support and repair the chopped out truss. The offending plumbers are long gone . They probably informed the GC who did nothing about it. Thanks for any suggestions
You'll need to header off the cut truss. This will transfer and redistribute the load on the cut truss to the adjacent trusses. To do this, you'll need to remove the tub because you'll need the space to work, or you can do this from the room below and cut the ceiling for access. Either way, I would still recommend moving the tub so you don't have to deal with the weight. Support both sides of the truss cut truss from below. For the headers, cut out a section of the sagging truss where the p trap is. Sixteen or so inches should suffice. Cut two 2x12s long enough to run perpendicular to the cut truss between the adjacent trusses, then cut two more for the other end of the sagging truss. Cut four pieces of ¾" plywood as long as the headers, and as wide as the truss, then fasten two to each 2x12 header. So now you have a box around the p trap. If the drain line needs to run through the header, just cut a hole through it to run the pipe. Putting in these headers is structurally sound, and should also satisfy local code. Also, keep in mind that this is not a trivial task, and I wouldn't recommend a casual diyer doing this. I would instead find a local carpenter with experience in this area.