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Mosaic techniques for outdoor table tops, patio floors, fountains or birdbaths

Indoor vs. Outdoor

Our regular mosaic instructions page is written for indoor mosaics not subject to standing water such as a shower floor. For these indoor mosaics, wood can be used as a backer, and we recommend the “glue-then-grout” method using Weldbond glue, a water-based PVA adhesive with no fumes.

However, outdoor mosaics and wet mosaics like pools and fountains require different backers and cements. First, wood should never be used as a backer for outdoor mosaics, even those kept relatively dry. The reason is that wood swells and contracts due to humidity changes in the air, and tiles will start to fall off eventually, and usually sooner than expected. Instead of wood, use 1/4″ concrete backer board for your outdoor mosaic projects. For attaching the tiles, use thinset mortar instead of adhesive. Thinset and concrete backer board is available at building material stores.

We carry convenience sized thinset mortar here.

All that being said, if you do want to mosaic something wooden for outdoors, such as a mosaic birdhouse, use thinset mortar to attach the tiles and make sure that every surface of the birdhouse not covered in mosaic is covered in multiple coats of exterior paint. You should seal the mosaic with multiple applications of a tile and grout sealer a few days after the grout cures. Even then, the life expectancy of such a project will be relatively short if exposed to the elements.

Outdoor Backers

Do not use wood as a backer for outdoor mosaics. Use 1/4″ concrete backer board, which is available at building material stores and is cut by scoring with box cutter and snapped along a straight edge. Masonry, concrete and stone are also good outdoor mosaic backers. Masonry can be smoother by plastering with thinset a few days (preferably 2 weeks) before the mosaic is applied. Fieldstone and pre-made concrete stepping stones from the lawn and garden center are good for smaller projects such as mosaic plaques and mosaic stepping stones. All stone, masonry and concrete should be scoured with a wire brush prior to applying thinset in order to remove contaminant and invisible concrete sealers which could interfere with bonding.

Avoid the use of terracotta bases for outdoor mosaics, as they can be extremely susceptible to freezing damage.

Read more about outdoor backer materials and methods in our article, “Backers for Outdoor Garden Mosaics.”

Outdoor Adhesives

Use thinset mortar instead of adhesives for outdoor mosaics. Most people find it is easier to mix up small batches of thinset than it is to use a solvent-based adhesive.

We use Versabond brand thinset which comes in a 50-pound bag. Buy a 5-gallon plastic bucket with lid at the same store you buy the thinset and put the bag directly into the bucket without emptying it (which would create an enormous amount of dust). The bucket helps contain dust and keeps humidity from ruining the mortar over time. Slit the top of the bag and use a long-handle spoon or garden shovel or ice scoop to take out what you need. The mixing ratio is 1/4 cup water per pound. Wear a dust mask and scoop and mix the thinset outdoors.

I have written some instructions for how to use thinset for detailed mosaic artwork where the artist wants to mount one tile at a time.

Outdoor Grouting

For outdoor projects, we will often use thinset mortar for grouting. We do this for two reasons: the thinset will match any thinset that squeezed up between the tiles, and thinset is harder than grout.

Outdoor Tiles

Glass tile is impervious to moisture penetration and therefore resistant to freeze damage. On the other hand, unglazed ceramic and tumble-finished stone are porous and highly susceptible to freeze damage. We avoid soft ceramics for use outdoors and always seal our finished mosaic with multiple applications of sealer to prevent damage. Even if glass tile is used, the porous grout is still vulnerable, so we always seal with multiple applications.

Outdoor Sealers

Outdoor mosaics should be sealed to protect against staining and freeze damage. There are two types of tile and grout sealers: penetrating pore sealer and coatings that form a membrane on the surface. Penetrating sealers soak into the pores of the grout, stone and ceramic. These pore sealers are usually made of latex or silicone, and they’re invisible. The membrane-forming sealers are coatings that create a hard, glossy finish and may change the color of the grout (usually by making it look darker). Concrete sealers tend to be of this second type.

TileLab SurfaceGard Penetrating Sealer made by Custom Building Products is a high-quality penetrating sealer. It’s water based, easy to apply, cleans up easily, and repels dirt, water, oil and stains. When applying a sealer, let it dry for two hours and then apply a drop of water to a grout line. If the water beads instead of soaking in, the grout is adequately sealed, which can usually be accomplished in two coats. I always put one additional coat to help ensure I plug any random pinholes.

Outdoor mosaic tables are often made by covering metal patio tables with concrete backer board insets which are then covered in mosaic. For any project using concrete backer board that is left exposed, it is important to seal the bottom and edges of the backer board to prevent water from penetrating the porous concrete. NOTE: You never want to seal any surface before mosaic is applied to it because the sealer will interfere with bonding.

Further Reading

We have tons more info on outdoor mosaic on our blog.

We recommend the following book for more information on outdoor mosaics:
Outdoor Mosaic: Original Weather-Proof Designs to Brighten Any Exterior Space by Emma Biggs and Tessa Hunkin

How To Make A Mosaic

These instructions are for an indoor mosaic not subjected to excess moisture. The mosaic process is similar for outdoor mosaics (such as pools and fountains) but thinset mortar is used outdoors instead of Weldbond adhesive. For wet mosaics such as shower floors, you also need to use thinset. Thinset is a sticky concrete with polymers added for strength, adhesion and water resistance.

More information on outdoor mosaics, specialized topics and advanced mosaic methods can be found on our Outdoor Mosaic Guide.

Our FAQ page also contains additional mosaic instructions, tips on using thinset and answers to many specific mosaic questions. It is constantly being expanded and has solutions for many common mosaic problems. Also, here are some tips on how to avoid disasters while grouting.

For an indoor project not subjected to moisture, it is very simple:

We carry everything you might need to make a mosaic:

See the Mosaic Tips below for more help with your mosaic.

Mosaic Tips from Our Resident Mosaic Artist

• Start simple.
• Make a small mosaic plaque before you mosaic a wall or floor. That way you can work out your materials and methods before the big job.
• How can you draw a design? Simple drawings like those in a coloring book work best. The color and the details come when you add the tile and glass. I always sketch something on paper and then come home and draw a simple cartoon on my plywood or concrete board using a magic marker. If drawing is a sore spot, you can create mosaic patterns easily without drawing as well.
• My first rule of grouts is to choose a contrasting color. If you use white grout with white tile or grey grout with grey tiles, then the tiles don’t stand out from the grout, and most of the detail of your design will be lost. When in doubt, black grout is usually the answer.
• My personal second rule of grouts is that DARKER GROUTS ALMOST ALWAYS LOOK BETTER. I have almost always been disappointed when using plain white grout. White grout makes a nice mosaic look like a summer camp project! Try an off-white or light beige if you think you need a light color. Also remember that grouts are much darker while they are wet and get lighter as they cure.
• Don’t know anything about glues, grouts or tiling? Your local hardware store or handyman is a mosaic expert even though they’ve never made one. (You might not know anyone who has made a mosaic, but you probably know someone who has tiled a bathroom or kitchen. The technical skills are very similar.)
• Use a wheeled glass cutter to cut glass and smalti. Use a tile nipper to cut ceramic tiles, china and other dishes.
• Always wear safety glasses when cutting tile or glass or mixing grout. (Grout is mildly caustic and has sand and grit in it.) Making a mosaic can be fun but you should always be careful.
• Grout mosaics outside. It’s a messy process. Look at books on home improvement for basic techniques of grouting if you’re not sure. Keep grout damp as it cures and do not allow it to dry out rapidly, otherwise it will crumble. Remember, the grout is binding water internally in a chemical process as it cure. It is NOT drying.
• Keep mosaic tiles and supplies out of reach of children. Use caution when handling the broken glass and ceramics.
• Spend a little more time on your mosaic. Don’t rush and don’t think about what you want to make next. It can make a world of difference in your satisfaction.
• Avoid plywood as a backer unless you can seal the edges and bottom. Wood materials absorb water over time and warp, and then grout and tiles pop off. You might not be trying to recreate a timeless Roman mosaic that will endure for centuries, but at least make something that will last 2 or 3 years. Use plywood at least 1/2″ thick inside and concrete or concrete board outside. Always use concrete or concrete board as the base of any mosaic that will be walked on. Concrete board can be purchased from building material stores. A common brand name is Wonderboard. For my indoor mosaics, I laminate 1/4″ Wonderboard to cabinet grade plywood backers.
• The best all-around glue for making mosaics is Weldbond. It is a water-based adhesive that looks and handles just like plain white glue, yet it cures stronger than many of the smelly solvent-based glues. The manufacturer’s brochure calls it “the most versatile, non-toxic, non-flammable adhesive on the North American market.” I agree. It bonds to hundreds of different materials and is very water-resistant once it dries. It cleans up easy with soap and water.
• If you make a mistake, don’t be afraid to pry some of the tiles off if you don’t like what you see. (Wear goggles or safety glasses with side shields.)
• I always wait for a week or two before I grout a piece. That way I have a chance to change things before they are literally set in concrete.
• Simple and crude can also be noble. It’s ok if your art has blemishes and mistakes. That’s what makes it interesting and keeps it from looking like it was made on an assembly line. Don’t try to make it a perfect reproduction of anything, and you’ll probably be much happier with the time spent and the results.
• Avoid making copies of phony arts-n-crafts stuff. There’s way too much of that around. Make your mosaic YOUR way and it will be genuine art in the highest sense of the word.

Legal Disclaimer and Copyright Information

No warranty is implied by these instructions. Use at your own risk. Please wear goggles when cutting mosaic materials or mixing grout. Mosaic materials are often sharp. Keep out of reach of children. Do not overload patio tables with mosaic materials so that the table becomes unstable (top heavy). You should also make sure that the table frame can support the overall weight. Copyright 2009 J.E. Moorman. Please link to these instructions freely, but email us if you would like to reproduce them for classes, etc.

There is nothing unique about mosaic grouts. The grouts and sealers used for mosaic artwork are the same ones used for ordinary bathroom tiling, and the techniques of applying the grout are the same. If you are ever uncertain and need information in a pinch, you can ask questions at your local building material store or look at their book on how to tile or bathroom repair, which they usually keep on the same aisle where they sell grout and supplies or in the plumbing department or near the registers. The point is that grouting isn’t rocket science and most handymen and women have done it before.

We carry everything you need to start grouting right away.

Estimating How Much Grout Is Needed

How much grout you need depends on three things: the area of the mosaic = L x W, the thickness of the tiles and the gaps between the tiles. If the tiles are well-spaced (all gaps under 1/4″), then you should be able to cover the entire mosaic of 18″ x 18″ with 2 lbs of grout. This is assuming your tiles are under 3/8″ thick. I always set my mosaic on an old shower curtain or piece of plastic to catch all the wet grout that falls off the side as I’m spreading it. That way I can scoop it up all the dropped grout and re-use it. Otherwise you need a lot more grout because most of it is wasted when it falls on the dirty floor.

If the gaps between your mosaic tiles are greater than 1/8 inch, then you may need grout with sand in it, such as we sell. The sand reinforces the grout to prevent cracking if the gaps are greater than 1/8 inch. Note that standard grout gaps are usually about 1/16 inch.

How to grout a mosaic

Selecting a Grout Color

I always choose a grout color which contrast the colors of the mosaic tiles so that the design is highlighted. Otherwise the individual tiles run together and are lost to the eye, and the mosaic looks more like an ordinary picture and less like a mosaic made from pieces. I avoid situations like gray grout with gray tile. A nice red-brown terra cotta grout works better in that instance. The key concept is color contrast instead of matching colors.

Color is best provided by the tile, not the grout. In terms of a visual element, the grout is supposed to act like a thin gray pencil line whose only purpose is to make each tile distinct. I don’t think I’ve ever seen a mosaic that used colored grout that wouldn’t have looked better if all tile had been used instead. For example, let’s say you wanted red tile in pink grout. A better way to get the same color effect would be to mix in a few pink tiles randomly throughout the red tiles, or maybe use a few lines of pink tiles. Often this means you have to cut your tile just a little bit smaller. That being said, it is possible to dye grout.

Dyeing Grout

There are mineral concrete dyes sold at building material stores, and these can be used, although the range of colors is limited to black, brown, gray, terracotta, etc. Vegetable dyes such as food colors will not work. You can use artists acrylic paint to color grout by mixing it in the wet grout. I recommend experimenting with tiny batches of grout and letting it harden before grouting a mosaic you have worked many hours on.

The Best Grout Color

Sometimes it is hard to decide which color grout to use because your mosaic already contains so many colors. The best color grout to use for most mosaics is black. Here’s why: The purpose of grout in visual terms is to make each tile distinct in the same way a pencil line in a watercolor is used to provide definition but not color. Black provides just enough contrast to most colors, unless you have black tile, and then you might want to consider something else.

Avoid pure white unless you are trying to make something that looks like a little kid’s summer camp project. Most building material stores such as Lowes and Home Depot cary about 30+ colors of grout. We carry the most commonly needed colors. Bring a few of each color of your tiles with you, and you can pick the color grout that works best with all the tile.

Grouting Stone Tile and Unglazed Ceramic

You should always seal unpolished stone and unglazed ceramic tiles with a tile and grout sealer BEFORE you grout. This is necessary for all porous materials that can be stained by grout. You should seal using a Stone Enhancer instead of tile and grout sealer if you want to darken and enhance the natural color of the stone. Both of these products are available at local building material stores. For a stone mosaic that is already stained, you might want to try some of the muratic acid that contractors use to clean cement from bricks.

Cracking and Crumbling Grout

You shouldn’t let the grout dry out as it cures. Cover with plastic if necessary. Lightly mist with a spray bottle, but don’t let drops accumulate on the surface of the grout. It also helps if you mix the grout according to instructions. It should be like a thick moist dough when you start with no dry material or lumps, and it should stick to your mixing wand, not drip, slide or crumble off.

Sanded Grout vs. Unsanded Grout

Don’t use unsanded grout. Unsanded grout is only used to fill hairline cracks. (Or it is mixed with sand for normal use.) If you use unsanded grout, then you can expect cracks in your grout and grout that isn’t quite as hard and durable.

Note: some tutorials incorrectly advise against using sanded grout because it might scratch the tile during grouting. Very few high quality mosaic materials will be soft enough to be damaged in this way, and you shouldn’t be using such easily scratched materials in any functional setting (bathrooms, counters, table tops et cetera…). Some ‘craft’ materials may have softer glazes which could be scratched by sand, but if you grout carefully the issue is easily avoided. There is no need to use a lot of force when grouting. If you have doubts about the durability of your materials, make a small test piece first.

If you decide to use unsanded grout, be sure to understand exactly why you are using it instead of the the stronger alternative.

Disposal of Grout Waste

Never pour grout down your drains. Grout is concrete, and that isn’t good for your plumbing. It will clog the pipes. I make a point of pouring as much of my grout sludge in an old cardboard box and allowing it to harden for disposal as solid waste. I always just dilute the dirty grout water and pour it in on my compost heap. The grout is a limestone product, so it actually helps balance the pH when there is excess decaying organic matter. Of course, this only applies to traditional grouts. I am not familiar with the synthetic epoxy grouts that some craft sites are selling. For easy cleanup, I always do my grouting in the backyard instead of indoors.

Ideas for small mosaic projects for beginners with examples

Mosaic Trivets and Mosaic Plaques

The best beginner’s project is a small trivet or plaque made on 1/2 inch plywood. I recommend cabinet-grade plywood which comes with a sanded finish. Many times you can get plenty of plywood in the scrap bin from a home remodeling job. Note that your backer doesn’t need to be perfectly square. Irregular triangles and rectangles and trapezoids work as well as squares. Remember to be “artistic” and “color outside the lines.”

If you desire to make a mosaic shape like a star or a cat or a sun, then 1/2 inch sanded plywood is still the best way to go. You can buy an entire sheet of plywood and a jigsaw to cut it with for not much more than what most craft websites charge for mosaic backers. Another advantage of cutting your own shape is that your project is more likely to look like YOUR art instead of some factory-made craft kit, which is all I can think of when I see the mosaic shapes or mosaic backers sold elsewhere.

The exposed edges of your plywood backer can be painted with a neutral color of acrylic paint or even latex house paint. You don’t always have to buy something special to make art, and you can often use what you happen to have on hand. In fact, using re-purposed materials usually adds an extra dimension of creativity to your project.

Displaying small mosaic plaques is simple: they can rest on a table as a coaster or trivet to hold hot plates, or they can be displayed on a small plate easel, such as people use to display fine china plates.