Yeah, it’s been a while since we discussed this but I can only do so much around here.
Anyway, I scraped out the caulk that the previous owner tried to fix the crack with. Like that had any chance of actually working! I had a small access hole through a bedroom wall to under the tub and I slipped in several small sheets of 1/2″ plywood under the improperly supported tub and worked them into position. I drilled a half dozen holes in the bottom of the tub plus one hole at each end of the 8″ crack. I then shot low expansion foam through the holes to build up some support between the tub and the new sub-floor. I then sat in the tub for the next 30 minutes to keep it from bowing. I cut off the excess foam that came back up the holes, sanded the whole area with 50 grit discs on my random orbit sander, cleaned the whole area with Acetone and sanded it again and cleaned it again. I cut two pieces of fiberglass mat, one about two inches bigger than the other. The small one was about three inches bigger in all dimensions than the repair area. A layer of resin, and a layer of fiberglass pressed in good and flat. Another layer of resin and another layer of fiberglass followed by a last layer of resin.
After three hours I started sanding going from 50 grit to 80 grit to 220 grit. I just kept running my hands over the patch trying to get it blended in as perfectly as possible. The final result was a solid tub bottom and a patch that blended in almost perfectly. Granted it’s an ugly brownish color instead of white but it feels and looks good. I filled the tub with water and stood in it. No leaks downstairs! If the patch holds for a few weeks I’ll buy the two part epoxy paint and redo the tub in white.
No matter what it was worth trying. The other option was a $3,000 bathroom tear out and a week or so of hard work. The bathroom looks to be all but new. It was just done poorly. Hopefully I just spent $30 on a $3000 fix? We will see in the next few weeks.