Ben wrote:

I have a stone walk from the front of my house to the driveway, which
has three steps. The stones that form the top step have come loose
and I want to reset them. These stones sit half on dirt and half on
other stones that serve as risers from the step below. I couldn't
tell if there was any gravel or sand used under the half on dirt. For
the other half, it looks as though something was used between the
riser stone and the step stone, but roots have grown in between and
compromised whatever was there.

Any suggestions as to how I should reset these stones?

Here's how a handyman would do it:
* Remove the loose stones.
* Make sure all remaining stones are completely stable. If not, remove
those too.
* Remove half an inch of the dirt underneath the tread.
* Remove the mortar that was sealing the tread to the riser.
* Compact the remaining dirt. You can pound it with the end of a 4x4
if you don't have a compactor. Get it good and solid. Add more dirt and
compact it until you have about half an inch of room between the dirt
and the tread. It will probably line up with the top edge of the riser.
* Put a bed of mortar on the dirt and the top edge of the riser.
* Moisten the back of the stones, then butter them with a thin coat of
mortar. This makes them stick better to the mortar bed.
* Position the stones where you want them. Make sure they tilt toward
the front just a little so water drains off.
* Tap the stones with the butt of your trowel to seat them.
* Put mortar in the joints.
* Smooth the joints with your finger. Don't forget the one under the
front edge.
* Use a damp sponge to clean off the mortar on the stone face.
* Double-check that the stones are positioned properly and tilt
forward for drainage.
* Put up barriers inside and outside to keep people off for 24 hours.

Now's a good time to put your initials in there somewhere for
posterity.

--
Steve Bell
New Life Home Improvement
Arlington, TX