This is a joint for sealant, not grout/mortar.
It is a continual source of movement.
Casey

Mortar never "connects" anything; it isn't glue. It is a bed upon which other things are set. Grout acts the same.

You need a flexible sealant such as polyurethane or silicone caulk in this application and because it's a change in plane.

The installer did not follow the TCNA (tile council of North America) guidelines. Any time you have a change in plane - the joint should be caulked.

Have him come back, remove the grout from the joint and install a 100% silicone caulk.

Silicone is not recommended for cement because it gives off acetic acid as it cures and that will not bond.
Use a specific sealer for masonry expansion joints.

Here is a link that might be useful: Sealant for Masonry

Caulk must meet the ASTM C 920 standard in this application. GE Silicone ll and DAP silicone meet this standard as does Loctite PL S10 polyurethane:

Here is a link that might be useful: 920

This post was edited by Trebruchet on Wed, Nov 26, 14 at 21:34

Perfect! Thank you kindly to everyone for your input. I'm going to purchase the LOCTITE Concrete Crack Sealant. That seems to be the way to go. I sent the photo to the hardscaping contractor that did the work. He mentioned that I do the same thing, and that it will not compromise the structural integrity of the steps.

bobby~

bobby:

If you are an inexperienced caulker, I'd highly recommend you mask the area thoroughly. Polyurethane caulk is some of the stickiest, gooiest, stuff on the planet; you only want it where you want it. Have some acetone handy, you're going to need it.

why isn't contractor doing the work?

Mortar adheres porous masonry materials together; grout fills a joint/space.

The tile joints can be filled with frost proof grout if the tile is resting on the same stable support. Where the tile meets the house that is not the case. Its like the joint between your tub and a tiled wall; it must be filled with a sealant that adheres well to both sides of the joint and can stretch as the subsurfaces move.

For a long lasting joint it is good to first install a closed cell foam joint backer rod so the sealant will take on an hourglass shape (thin at the middle). Silicone sealants should not be used on horizontal surfaces where water will stand.

The best solution for exterior steps is to avoid grouted joints because they will eventually fail and can cause injury. A better material would be full width stone treads set in mortar with no joints or sealants.

Trebruchet: good lookin' on the 'acetone' tip!