You will have to remove it all as it will continue to crack and crumble I think he might have used the wrong grout for the job unsanded versus sanded for instance.

@Patricia and other pros: What is a reasonable amount of time to expect that particular seam between the counters and the backsplash to stay strong? Our kitchen is about four years old and in a few places around the sink area the grout/caulking is beginning to crack and crumble just at that bottom seam. Obviously it should last more than six months, but does it usually last as long as the grout between the tiles? Or is it more prone to degrading, cracking, and crumbling because it gets more exposure to water and is connecting vertical and horizontal surfaces?

Was it grout or caulking that was used? We use a caulking for the area between the granite or quartz and tile, simply because it lasts longer. Caulking will still need to be replaced over time, but not every 6 months.

Thank you for your feed back. It was sanded grout. It only seems to be happening where the grout meets the granite, wall, cabinets and window frame. Everything else is fine. Perhaps the caulking in those areas would have been better.

This has nothing to do with the "wrong grout". Any place that tile either changes plane, or abuts another surface, ESPECIALLY WOOD, that joint needs to be caulked. No matter WHAT grout you use it will continue to crack out.

I really wish I had hired a pro that knew this! Mine did a horrible job and was rude while doing it! So I need to put in sanded caulk where the tile meets the quartz countertop? That’s the only place I’m getting crumbling as well.

Our caulking had to be redone after six months. It was installed in summer and just started cracking. We were told since it is an exterior wall the changes in temp can cause that. They were great and came right out to fix it.