How to Make A Mosaic Waterproof?

Are you working on a mosaic project? Maybe you are wondering how you make it waterproof. We've researched the techniques and materials you can use to waterproof mosaics.

By using the proper sealant, you can make any mosaic piece waterproof. Typical grout sealants used for mosaic pieces include penetrating, membrane-forming, and concrete types. Apply several coats of sealant to the grout, and make sure to wipe it off of the tiles or glass for a flawless finish. The type of sealant you choose depends on what you prefer for the finish and the type of tesserae used. 

Keep reading for step-by-step instructions on how to mosaic a base and how to make it waterproof to be used or displayed either outdoors or indoors. In this article, we will discuss types of adhesives and sealants, so you can complete a beautiful, long-lasting project.

A colorful mosaic art photographed at a top view, How to Make A Mosaic Waterproof?

How To Waterproof a Mosaic

Let's start at the base and work our way through your mosaic project so you can complete a water-resistant work of art. By properly adhering tesserae, then applying grout, and finally sealing the mosaic, you can be certain that your piece will be preserved as well as protected from water, and UV exposure and stay remarkably easy to clean.

The Base

First and foremost, you will need to find the perfect base for your mosaic project. This can be a small side table, birdbath, or maybe even an old chair. It is best to sand down the surface on which you will be applying the tesserae. Sanding the surface allows the tiles or pieces that you will use to adhere better. If you are using a metal base, you should also rough up the surface using sandpaper so that the tesserae will cling.


The term tesserae refer to the materials you are using in your piece for the mosaic part. This could include small tiles, broken pieces of pottery, glass, or even seashells. You may have a design already planned that you want to use. First, draw out your design with a pencil on the surface of your base. Then apply the tesserae with a strong adhesive (or glue), such as the one shown below. Click here to see it on Amazon.

Please note, some artists also use small amounts of the thin-set mortar instead of adhesive (or glue) on the back of their tesserae (more on this in the next section). The type of adhesive used is entirely up to you.

Thinset Mortar

After adhering tesserae and allowing setting-time, you will want to apply your thin-set mortar. If your mortar needs to be mixed, follow directions to do so and get ready to fill in the cracks. You can use a little shovel to mix or a spatula. It is recommended to wear gloves when working with any grout.

Smear the mortar into any crack or blank space that does not have a tile or whatever material you are using. After it is in place, use your clean cloth to wipe the excess off of the tesserae before it dries. A sponge may be used as well. You do not want the mortar to become hard in areas where it is not wanted. It will not be easy to remove after hardening. Click here to see it on Amazon.

Drying time for thin-set mortar will vary based on humidity and how much product was used. It can take anywhere from 24- to 48-hours for the grout to fully dry and set. After it is completely dry, the mosaic is now water-resistant and can be put outside or even used inside.


Outdoor mosaics are best protected by applying a sealant, typically a tile or grout sealant. You have several options for types of sealants including penetrating, membrane-forming, and concrete sealers. All types seal your mosaic to prevent staining, UV damage, and freezing as well as make the surface easier to keep clean.

A penetrating sealant is best used on porous surfaces like ceramic, terracotta, and stone. These provide a transparent finish, water resistance, and UV barrier to prevent fading. Click here to see it on Amazon.

A membrane-forming sealant creates a glossy finish and a somewhat hard surface. Concrete-type sealers are typically membrane-forming. These sealants can alter the color of your mosaic, by darkening the surface. So, you might want to apply first to a small area to be sure you will be pleased with the result. Click here to see it on Amazon.

What Surfaces Can You Mosaic On?

You can mosaic virtually any surface, provided the area is inflexible, clean, and free of grease and paint. Some of the most common surfaces include medium-density fibreboard (MDF), plywood, cement board, glass, and metal. However, you can also use:

  • wood
  • stone
  • terracotta
  • ceramic

Stepping stones for the garden are a unique base and trendy mosaic project. Watch the video below, on YouTube, to see how to make your mosaic stepping stones for your garden!

Can Glass Mosaic Tiles Be Used Outside?

Ceramic or porcelain glass pieces are typically used for outside mosaics. They are more durable for outdoor use. Once mortared in place, they are pretty resistant to the elements. However, they can still crack if something hard falls onto them or hits the piece.

What is the Best Glue for Outdoor Mosaics?

Thin-set mortar is highly recommended for outdoor mosaics. It is a sticky concrete that has added polymers in it. It is quite durable and will withstand outdoor elements and prolonged usage. However, there are several other adhesive options for water-resistant projects such as silicone (typically used on glass), and epoxy (typically used on metal).


WeldBond is a universal adhesive that works well on mosaics but is not recommended for outdoor projects because it is a PVA-type glue. This product is water-resistant, and the non-toxic formula creates a bond between virtually any material (cement, brick, plaster, metal, glass, and wood, among others). Your mosaic will look flawless with the clear-drying WeldBond keeping everything in place. Click here to see it on Amazon.

Liquid Nails

A heavy-duty adhesive solution, Liquid Nails can be used for mosaics that will endure the outdoor elements. It bonds within minutes on various surfaces, including concrete, brick, and tile, to form a water-resistant seal. Please refer to the manufacturer's instructions for approved materials before applying them to your mosaic project, as there are different types of Liquid Nails formulas. Click here to see it on Amazon.

Gorilla Glue

You might already have Gorilla Glue in your house, but did you know you can use it for mosaics? This adhesive forms a quick bond and can be used on plastic, wood, ceramic, and more. You might prefer this for detailed projects using tiny tesserae. Click here to see it on Amazon.

What is the Best Grout for Mosaics?

There are many types of grouts on the market that can be used outside in the elements. As stated above, a thin set is a great idea for small tables, stepping stones, or birdbaths. For patios or larger projects, Jennifer's Mosaics Powdered grout can be used. It comes in numerous colors, including terracotta, black, gray, and white. This type of grout can also be used indoors! Click here to see it on Amazon.

In Closing

Man different mortars or grouts can be used to make a mosaic waterproof for use indoors or outdoors. They come in a wide range of colors and really add life to any mosaic project. They hold up well in outdoor elements and are fairly easy to use. Mosaics are not only fun to create, but they add a lot of beautiful elements to your patio or garden!

For other crafts and ideas using glass, visit these articles below.

This Post Has 4 Comments

  1. Paula

    I’d like to apply mosaic to a rock for outdoor garden. If I set tiles in thin set do I need to seal the thin set like I would if grouted? Also do you recommend sealing rock with anything prior to adhering tiles? Thank you

  2. Angie Ross

    I want to know the answer to the same question.

  3. Toni

    How can I seal a porcelain mosaic table top so that it has a smooth cleanable surface. Is there a preferred resin that would level the surface?

  4. Howard

    Thanks, now I can work on several outdoor Mosaic pieces and fix the patio table I have repaired twice due to weather damage.

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