Building a garden pebble mosaic

My borders and plants have been very neglected this season, as I’ve been putting lots of time into two big garden projects.  The first was my beautiful greenhouse, which arrived in April and now looks like its been here forever. My second has been building a large pebble mosaic bee in the front garden. 

This project was inspired by the work of Maggy Howarth, the leading authority on pebble mosaics in the UK.  Her work can be found in public parks and urban spaces across the country, as well as in private gardens and show gardens.  I love her mosaics but would never be able to afford the real thing so decided to create my own.  Plus, pebble collecting is very addictive – there’s something very meditative about walking along a beach searching for the perfect pebble. There must be a dormant hunter-gatherer instinct in all of us.  A mosaic gave a purpose for my growing collection.

Some warnings first – this wasn’t easy, or quick, and was quite expensive because of the amount of aggregates used.  Certainly not a weekend project and, as is the case with many of these things, it was 90% groundwork and 10% artistry.  However, it was very rewarding and I am pleased with the final result. 

I used the methods described in Maggy Howarth’s book ‘The Pebble Mosaic Handbook’. I also, rather cheekily, copied her design from a bee mosaic I had admired at Gresgarth Hall, Lancashire.  This feels rather like I’ve cheated but I hope its viewed as a homage rather than plagiarism. First attempts at my own bee designs were terrible.

Rough instructions are below, but for step-by-step instructions and diagrams, Maggy’s book is really excellent.

1. Decide on your design and figure out what pebbles you need. Some pebbles I already had in my collection, some came from garden centres and B&Q, some were from beaches and rivers, others begged from friends’ garden features.  Getting everything together can take a few years if you are only collecting a few at a time, especially if you live somewhere landlocked. Friends were even sent on their seaside holidays with specific instructions to bring back three grey pebbles of a certain shape and size.   The surrounding stones are just regular Sheffield stones of local millstone grit.

2. Because I wanted to be sure that I had the design right and enough stones, I first tried out the bee design in a sandbox made from old planks (although I didn’t build it large enough to accommodate the wings).  Once you start the real thing you are committed, as your dry mix will harden so everything needs to be to hand ready to use.  There won’t be time to go shopping for more pebbles mid-construction. I also made a paper template of the practice bee.

3. To make the mosaic sturdy and frost resistant, it needs a solid base.  I dug out the area to eight inches depth.  This took a very long time as I had to excavate a huge pyracantha root as thick as my arm and also lower some of the surrounding flagstones so they didn’t impede drainage.  There were also quite a few journeys to the tip to get rid of the spoil.

4. To stop the mosaic collapsing outwards you need a solid border to hold everything in place.  I re-used old pond edging stones from the garden. You also need to make sure the edges are level, and that the whole mosaic slopes slightly downhill away from the house for drainage.  I had a difficult job heaving these heavy stones into position and broke both my trowel and the tip of my little finger in one day.  Progress was very slow at this stage with my finger strapped up.

5. Next you need to half fill the hole with four inches of Mot sub base.  This is a sort of rubbly, dusty mix that you buy in from the aggregate section of hardware stores. Again, I hit a block at this point as it coincided with the COVID induced shortages in DIY shops and there was not a bag to be found in the whole of Sheffield. The whole project got covered in a tarpaulin for a few weeks until they re-stocked.  I also underestimated just how much sub-base this would require and had to go back twice for more.  Maggy recommends hiring a whacker plate to get the base packed down properly but I only had a small area so tamped it down with a fence post.  The bamboo sticks  in the photo are to give a rough measurement of the final mosaic.    

6. Now the fun bit!  Mix a dry mix of sand, grit and cement.  You need dry weather for this and only mix a bucket at a time or it will go hard. Insert the pebbles into the dry mix and tamp down with a bar of wood to level with the edges. The pebbles need to be touching and inserted vertically.  I made a cardboard outline of the bee to keep to my design but a wooden template would be better.

7. Laying the pebbles and surrounding stone took me a week of evenings, and I was blessed with dry weather throughout. I used bricks to hold the most recent pebbles in place overnight but ideally you would take a few days off work or do it over a full weekend.  Laying the gritstone surround was like doing a jigsaw without knowing if you had all the pieces and required a couple of desperate hunts round the garden when I needed a particular shape for a missing piece.

8. The wings are made from slate pieces and decorative glass nuggets. The glass nuggets were very slippery to handle and required a finer dry mix with less grit than previously.  I bought some of these online and some in Wilko’s and used a mix of colours to give a dappled effect.

9. Finally, I sieved a very fine dry mix over the mosaic, brushed into the gaps like a grout, and thoroughly sprayed with water.  Maggy recommends covering it all in polythene and leaving to cure for a month, but I was so busy admiring it that I forgot this stage. It seems to have suffered no harmful effects.

10. After a few days I noticed that the mosaic wasn’t entirely level and water was pooling in one or two dips.  With the dry mix not quite yet set, I made a drainage hole in these areas with a tent peg and covered loosely with a pebble. These holes aren’t visible and allow any rainwater to drain away. 

11. The verdict.  I love it! There were times in the process when I felt like I had really bitten off more than I could chew.  However, I would certainly be tempted to do another one but make it smaller and use mainly local gritstone, which is much easier to come by.  Mosaics make a really interesting addition to any garden and there are lots of ideas for smaller beginners projects in Maggy’s book.