grout sealer

[kurt]

Sometimes yes, sometimes no. Big fat joints (3/16") will inevitably open up; how much is unknown, but it's usually 1/32-1/16.

Or not. Depends.

[John Dirks Jr]

Maybe I'll pack the flexible caulk deep in the corner joints and face the joint with the cement based to get the perfect color match. If the cement opens up, the caulk will be there underneath. I think I just need to save enough room for the cement so that is has a decent thickness which can support itself.

[Chad Fabry]

I grout the corners. The caulk gets all yucky.

[John Kogel]

I second that, grout the corners. It won't hurt to try and it looks better than caulk with no maintenance.

I grouted my floor tiles to the tub about four years ago and that seam is still tight. Good quality grout.

You can try caulking with colored silicone if it opens up.