A friend with considerable landscaping experience, in return for me having embroidered her a quilt last winter, is helping me build a three-step flight of curving stairs up a grade at the side of my house out of chunks of broken concrete salvaged from a neighbor's driveway-replacement project. The individual arced risers are about six feet long, about six inches high and a bit more than a foot deep, so they register as a bit bigger than normal stairs. The two done so far already make me smile; they perfectly set off the curved drystone wall I laid myself adjacent to this grade. My friend is using the local clay to bed the chunks in, and is setting them so the back-end of each major chunk is weighed down by the front end of the step above. There are crevices now filled with clay she says I can dig out when we're done and backfill with good dirt to plant tiny thymes and such. We'll be using spare pieces to lay a wheelbarrow ramp adjacent to these steps.

The problem? We've got two of the three steps laid, and my friend says that none of the remaining chunks is big enough to do the last riser -- indeed, some of the second-riser pieces make her unhappy. She wants pieces six inches thick and a minimum of 24 inches long, though the widths can vary -- and the places I've called say they won't bust them that big because of the risk of hurting the workers who have to move them. I have many pieces in the 20" range, but my friend says these won't work. Is there a good reason we can't do sort of a mosaic for the top step using these slightly-smaller pieces, or even extending farther back from the edge? I thought of casting my own chunks, but I doubt I can match the rough-hewn texture of the rest.

I asked her about using mortar to hold the pieces, and she says she has no experience with that. Can you point me in any particularly-good directions for that?

Many thanks!

Lynn