Pebble mosaics—but without the cement

Recently, I've become very interested in pebble mosaics. For some really beautiful and ambitious examples, see here: https://www.maggyhowarth.co.uk/

For a range of more and less ambitious examples, see here: https://www.finegardening.com/article/create-a-pebble-mosaic

Rounded pebbles with flat sides are inserted into a concrete mix with their long dimension oriented vertically. That way, they stay in better. If they were oriented horizontally, they would come loose, even in mortar.

I'd like to build some small, simple pebble mosaics as decorative features. If possible, I'd like to avoid using cement mortar. It would be nice if they could stand up to light foot traffic without having to be rebuilt constantly without the high carbon emissions of cement.

I'm figuring that if I used wooden timbers as part of the design to break up the expanse of pebble mosaic into smaller segments, unmortared pebbles would stand a better chance of staying in place. I'm imagining laying the pebbles out over a compacted base, leaving them a bit proud of their final level, and then using a board to compact them flush with the surrounding timbers and lock everything together.

I'm in a cold climate with a certain amount of freeze-thaw. An unmortared brick path I laid over sand has stayed in good shape for several years now, so it isn't a terribly extreme climate for hardscapes.

Does this sound feasible?

What kind of base would be best under the pebbles? Sand? Crusher fines? Roadbase? Recycled Concrete? Lime-stabilized soil?

I am surprised you say there is no cement involved?
Cement is an additive to concrete, and these mosaics seem to be created by pressing the pebbles into a concrete mix laid on the ground.

Examining early Greek pebble mosaics, Maggy Howarth writes:

The ancient Greeks had simple tools,…limited materials and no cement, but inventive minds cannot be stopped. Wonderful things can still be made, whatever the means.

Complete Pebble Mosaic Handbook, 2009 ed., p. 89

YES, you can make pebble mosaics without cement! If freeze-thaw is an issue, keep the water away from the surface if possible. Here in the Albuquerque area, temperatures drop below freezing in the winter. Sometimes stones in my pebble mosaics will pop out of place but it is no trouble slipping them back in during the warmer months. The base material is sand-silt-clay, compacted by cars driving over the surface prior to building the pebble walking paths. The mortar is sand-silt-clay slurry made from the subsoil. This material is perfect because it is all that we have! Sturdy edges within the mosaic can help in high traffic areas. Pebble mosaics don't have to last thousands of years to be fabulous.
Best of luck with your creative process, Gilbert.

Thanks, Amy, that's great information!

Do you happen to have any photos of your pebble mosaics that you could share?

I've been thinking that including on-edge bricks, pavers, flagstones, etc. in the mosaics would give them more stability, as would adding bottomless flowerpots, metal hoops, or metal containers; these would divide the mosaic into smaller and more sturdy areas, and the circular rims visible on the surface could also be a design element.

I am amazed!
I will try it out myself, does the book mentioned advise about the sorts of soil components to be used?

Pictures of mosaics abound with a Google search offer much inspiration. Posting pictures of my work take a lot of time and won’t help others because the secrets are hidden from view: photos do not show the critical ugly underside of these designs. While Maggy Howarth’s book is invaluable to me, the painstaking intricacy and small pebble perfection is not possible using my locally sourced stones, nor does it suit my earthy landscape style. Her designs are beautifully urbane and functional for high traffic areas. Mine are plain and minimalist.

For my work, I use 4”- 6” slim broken river stones in larger abstract designs with maximum width of 18 inches. An 18” x 18” round stepping stone is typical. These are under trees, in the garden, on hills and on crusher fine paths. They are quickly assembled in a morning. After decades of learning, these are the main secrets of the success of quickly assembled robust river stone mosaics:
1. The ideal stone is a wedge shape (not a round pebble) that appears to be a large pebble from the top view
2. Most of the stone is buried so only one pretty edge is necessary (top of the wedge)
3. That smooth pretty top edge is the fattest part of the stone
4. What is buried is sharp, broken, rough, tapered and hopefully long enough to be tapped into subsoil with a wooden mallet
5. Backfill surrounding material to support the stone edge (additional edge supports are not necessary)
6. Use sifted local subsoil to make mortar (if needed) and for grout to anchor the imbedded design

My biggest recommendation for mosaics in permaculture landscapes is that the artist use what is at hand and common to inform style. Bring together the personal aesthetic and vernacular influences (limitations) of the area.

P.S. Avoid low-fire pottery edges in designs as they absorb water and break down quickly in freeze-thaw conditions. Explore any materials that can withstand your environmental conditions. Start small and practice often.

Hi, this is beautifully awesome!

What are your thoughts on using shale?
I reckon river rocks/pebbles are used for the durability. Shale maybe too fragile. It does tend to break down and compact...but I just happen to have a lot of shale. So I may try this one a small stepping stone of experimentation.

love this idea!
I found some wonderful images searching online, I want to try it

Regarding  avoiding the use of cement, what about a mix using cat litter?
I am referring to the really cheap clay stuff, some of which actually clumps like the more expensive brands.
A long time ago I was told that a lot of the clay litters had bentonite (sp?) clay in them which will reseal when it cracks. But it is more natural  while still supporting the stones and discouraging plants

I don't live where there is a freeze and I sometimes see mosaic paths where the path was leveled, edged, then a layer a sand it laid, then a layer of cob then the stones are laid and tampered down into the cob. A wet towel can be used to smooth out around the pebbles afterthe are tampered down. They seem to hold up reasonably well, especially if drainage was taken into consideration.