Create Your Own Outdoor Mosaic

R. L. Rhodes
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If you’re looking for a way to liven up your outdoor living spaces – or create an area to place your grill or fire pit – a mosaic is a great way to inject some color into your yard or patio.

And while installation may involve considerable elbow grease, the total cost of doing-it-yourself is much lower than you’d expect: the 4’ by 4’ pebble mosaic shown on this page was built for less than $100, and works perfectly as a decorative space for a number of activities.

While it’s technically possible to pull off a mosaic that size in a single day, it’s much less strenuous to handle this project in phases. The instructions below are divided into three day-segments to help you take advantage of your extra day of doing.

(By the way, if you want to delve into mosaic but find a large project like this daunting, you can modify the instructions below to create stepping stones out of smaller tiles. Or you could fill in the gaps of your existing concrete or stone features with decorative filler.)

Skill level: Intermediate

Time: 2-3 days, including time for letting the mortar set.

Materials:

  • Mortar
  • Pebbles
  • Furring strips, cut to fit
  • Gravel
  • Stakes (optional)
  • Twine (optional)

Tools:

Day 1. Getting your materials ready

Plan your mosaic. Having a design in mind before you start is essential. Having it on paper is even better. If you draw or print your design on graph paper, you can use stakes and twine to impose a corresponding grid on your workspace, which will help you place the stones in a more approximate formation.

Gather your materials. Now that you know how you want your mosaic to look, time to find the right materials. For example, the furring strips listed in the materials are thin planks of wood used for bracing the plot. Drawing out your design ahead of time allows you to calculate the length and number of furring strips you’ll need. Planning ahead is particularly important if you haven’t already been collecting stones and pebbles. Luckily, the rest of us can buy bags of landscaping pebbles. But you’ll want to know in advance what colors to buy and how many bags of each. The mosaic shown in these pictures was assembled from white marble chips, red rock lava, and assorted river pebbles, all from Vigoro.

Sort your stones. If you’re working with a collection of stones that you assembled yourself – or if you’ve bought pebbles in an assortment of colors – you’ll want to sort them before you start arranging your mosaic. If you have to sort them while you lay them, you may find the mortar starting to set before you can get the stones in place. Sorting can be time consuming, so it’s suggested that you do this the day before you pour your mortar. Sort them into separate buckets, one for each color you intend to use, with enough water to cover the stones. Bagged stones in particular will likely be covered in grit from having rubbed up against other stones, and the water is useful for removing that grit.

Day 2. Laying the groundwork

Measure off your space. Try to choose a relatively level space for your mosaic. Once you’ve chosen a spot, measure off the dimension with a yardstick or measuring tape, allowing an extra inch in each direction for the furring strips. If you’re laying a square or rectangular plot, you can mark each corner with a stake and bound the edges with twine.

Dig a mold. Dig to a depth of 4 to 5 inches, depending on how much gravel you intend to use as a base. If your ground is prone to freeze during colder months, plan for a deeper base. Once you’ve reached the appropriate depth, place your furring strips along the edges. The fit should be rather snug, so you may need to secure them into place by tapping them along the edges with a hammer.

Lay the gravel. Try to level out the floor of the plot as much as possible, then pour in your gravel, leaving about 2 to 3 inches from the top of the gravel to the intended height of the mosaic. Press the gravel down to make it as flat as possible – walking on it works fine. Use the level to make sure the surface is even. Dampen the bed with a quick spray from your garden hose.

Day 3. Piecing it all together

Mix the mortar. From here on out, time becomes a factor, so be sure you have all of the needed material at hand. Dry mortar is an irritant, so be sure to wear rubber gloves, a respirator, and protective eyewear. When you’re ready, combine the mortar with water in a bucket. (Always refer to the mortar packaging for the proper ratio of dry mortar to water.) A mortar hoe will make stirring the mixture easier. The ready-to-pour mortar should have a thick consistency, with no powdery clumps. Mix only as much as you need to work on at the moment. You can always go back and mix more, but you can’t stop the timer on setting mortar once it’s been mixed.

Pour the mortar. When you’re done mixing, pour the mortar into the mold. If you’re ambitious and have designed a large mosaic, you’ll do best to attack it in sections. A 50 lb. bag of dry mortar will cover about 4 square feet. You can use extra furring strips to block off those spaces, as in the picture above. Once you’ve filled the area you intend to work on, distribute it using your trowel, taking special care with the edges and corners. If you’re working on one section of a larger mosaic, go ahead and place the stones before you mix and pour the mortar for the next section. Otherwise, you might find that the mortar has already set before you started your design.

Lay the stones. This is where you’ll finally start to see your mosaic come to life. With the mortar poured and smoothed out, you can start removing stones from the sorting buckets, shaking them to remove excess water, and placing them in the mortar. Press them in a little to make sure they mortar takes hold.
Having the stones waiting in water-filled buckets also allows you to rinse away any mortar that might cling to your hands in the process. Try to choose stones that fit relatively close together. The weight of the stones may shift the level of the mortar; after you’re done arranging each section, you can level it off again by pressing the surface with a board or a sheet of plywood.

If you’re building a large mosaic in stages, repeat the Day 3 steps as many times as needed. When you’re done arranging the stones, it’s time to let your mosaic set. Leave the furring strips where they are for now. Give the mortar 24 to 48 hours to fully dry and harden, fixing your pattern in place. When the mortar is completely set, you can pry away the furring strips and fill in the space with some of the excess soil you removed on day two. This is also a good time to limn one or more sides of your mosaic with plants, if you’re planning to do so.

Once finished, your mosaic can serve as a durable and decorative foundation for all sorts of outdoor activities. Use it to highlight your grilling station at backyard barbecues. Surround it with ferns and flowers and set it with a cast iron tea table and chairs for a cozy outdoor conversation space.  Or turn it into a quiet reading nook by furnishing it with comfy outdoor chair and side table.

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