Suggestions? You asked for it.

Hire a tile man that knows what he is doing.

Wood swells when it gets wet. That is why 95% of all shower curbs fail in North America.

I would rip all that tile out. Prepare the curb or dam for brick or concrete. Waterproof it all with something like Ardex 8_9 and then re tile and grout.

Then instead of the wood floor and dam swelling and causing tile pops you can see the water and wipe it up.

Better yet install a drain in that area so any mishap - the water has a back up plan for leaving the space.

Code requires laundry drains now. Most if not all new homes have them.

Traditional Laundry Room · More Info

Looking at the wood choice it appears they grabbed some scrap 1"x2" to build the dam....

often this is lying around after siding a house. I might further guess it is the pressure treated type. Not sure if the chemicals there caused the bond failure.

The International Residential Code ( IRC ) does not require a pan or Floor Drain for a Clothes Washing Machine. Nor does the IRC require any of that for a Dishwasher , Laundry Tub , or Toilets that may overflow. The only place it is required is IRC P2801.5 Water Heaters

Thank you all for responding to my question.

I do have a drain in that area for my washer, so I think I am okay there. As far as the tile, it is old and came with the house and we have been living here for about 16 years, so I consider myself lucky that it has lasted this long.

I will look into having the tile re-installed.

Aside from there being better ways to build a curb, this isn't something that failed from getting wet a lot and swelling the wood, or most of the usual culprits that cause them to fail in a shower that is used daily. While you could certainly spend thousands of dollars to get a top notch waterproofing system put in under the tile and slope everything to the drain 1/4" per foot etc, etc, it just isn't necessary for something that might see water once every ten years. It will dry out just fine from the occasional mishap.

It appears more likely that this curb gets stood on quite frequently, unlike a shower curb that usually gets stepped over. When you stand on a single piece of tile without four other tiles locking it in on the top of the curb, and lean against the washer, pushing the tile sideways, and twist and turn on it while taking the clothes from the washer to the dryer, it will eventually loosen the tile from the thinset no matter what is underneath.

While it would be silly to bother building a curb without having a drain, it is not necessary to follow all the rule that are necessary for a shower that is used daily. For instance, if you were to slope the floor to a central drain, your washer and dryer would slide together and make extra noise. It is also inconvenient to put a standard 4" wide curb right where you need to stand. Since you have actually had a water incident there before, you probably have a good idea of how deep the water got in the pan. With a floor drain, it should either be very little water, or the drain is clogged or undersized, and won't keep up no matter how high the curb is. If the drain is not large enough, it would eventually overflow.

That curb is not very tall anyway, and since I can't see the whole curb, I will assume it is just one side, straight, and about 5' long. The expensive way to provide some protection would be to put an additional line drain all the way across the front and flush with the floor, which would provide the most comfort and convenience. That is probably not the option for this time.

What I would do is tear out the entire curb while leaving the rest of the tile. Then build the area up where the curb was with floor tile underlayment so that it is flush with the top of the tile. Then go down to the stone yard or fabricator and find a remanent of granite or other stone from someone's countertop that is 3cm (1.2") thick. This should be all one piece to eliminate the problem of the smaller tiles. It should also be wider, so that it is more comfortable to stand on. It should go over the carpet 1/4" - 1/2" just like the carpet should go under baseboard. It should also go to within an inch or two of the front of the washer and dryer, which should make it more comfortable. This isn't a shower, but the joint between the floor and curb will be siliconed just like it is between the floor and the walls of a shower. The granite will go directly over the tile that is already there because you are not building a bathtub, just an emergency barrier. Because this would be one continuous solid piece, you shouldn't have any problem just using silicone or some other adhesive to attach the slab to the floor.