I thought you were in MA, not ME. The good news is that if it's the PT that shrank, it's done. The bad news is that if the soil is undergoing expansions and contraction cycles...it's unstable. I don't have a vast amount of experience working in clay, but I had a big bucks job in clay years ago. We actually set up something similar to a drip irrigation system around the perimeter of the foundation. The purpose was that the drip irrigation would keep the clay continually moist so it wouldn't undergo movement cycles as the clay dried and rewet. It'd essentially stay permanently wet and not move. Any excess moisture was removed by foundation perimeter and footing drains. Now, you wrote that the crawl space is sealed up... 1) For clarification, I'm assuming that there is a concrete foundation around the perimeter of this addition? Or is it built on piers? 2) If it's a poured foundation, was a rat slab (thin 2" poured slab) or a full slab poured in the crawl space? Or is the bottom of the subfloor open to soil on the ground? 3) With the clay, did your dad have any engineering analysis done with regards to soil movement or stabilization? As to "what now"...was this a Kerdi shower? Or did it have a topical membrane (HydroBan, RedGard, etc)? I remember your shower but forget the specifics of how it was built. If Kerdi, the cracks are sort of inconsequential when it comes to water penetrating into the walls. The cracks are more cosmetic unless they really open up. I'd get in touch with your installer regarding the details of the walls. Depending on how the walls were detailed/waterproofed might give you a warm fuzzy regarding letting things sit as they are while you see if movement has stabilized versus taking action (caulk the crack, etc) if water penetration may be a concern. I'd mark the ends of the cracks with blue tape and keep an eye to see if the cracks extend or if the movement has stopped or stabilized.

OP, Before you replace just the sink, consider the cost of replacing the entire unit. I have a very similar vanity/ top / sink that came from Lowe's and was not terribly expensive ($350). The one that you have isn't in bad shape, but if you wanted to change styles, or if it was otherwise damaged this would be an opportunity to swap it out. BTW: The bowl is probably sealed to the granite with silicone sealant - you will have to cut it from the top after removing the bolts. You don't use plumbers putty on granite. Also, the top is pretty much permanently attached to the base. I was going to take the top off mine when I brought it home to make the installation easier and lighter... I think it was epoxied on to the sink base. I do agree, however, that the sink is probably fine. If the crack gets bigger or leaks, deal with it then. Here is a link that might be useful: Sink and base This post was edited by jakethewonderdog on Wed, Sep 3, 14 at 9:02

Not a pro grout job. I had something similar, only worse, and it turned out that the backer board was not properly installed. It wasn't firmly attached to the studs. There was some movement and the tile cracked. The contractor come back and redid the whole wall, on his nickle. YMMV

Because it seemed important to know how bad the situation is, I removed the tiles and mudboard in the problem area. Underneath is just the sheathing. You can see that most of the wood is still in tact, but it's definitely rotted in the corner by the tub. That spot is still very wet, smells earthy, and I can dig into it with my finger. In a 4" x 4" area, I could make a little 1/2 inch hole easily. Now I'm wondering if the best solution might be to: 1) wait for wood sheathing to dry; 2) put down some kind of underlayer or mortar, and then 3) just put on some of that Flex Seal - as a temporary solution. Or, should I put down some kind of PVC board, or something like that over the sheathing - and then put mortar on that - just in case there's reason to worry about the sheathing in that corner giving in. and the PVC board would keep us from falling through the ceiling (until we do the full renovation)! Thanks everyone for your help!