How to Apply Mastic for Backsplash

Meta description: A step-by-step guide to properly preparing and applying mastic when installing a backsplash. Learn how to correctly use mastic adhesive for a long-lasting, water-resistant backsplash.


Installing a backsplash is an easy way to add personality and functionality to any kitchen. Often made of tile, glass, or metal, backsplashes protect the wall behind a countertop or sink from water damage and stains. While the materials chosen make a difference, proper application of the right adhesive is key for a backsplash that stays securely adhered to the wall. Mastic is a top choice for backsplash installation thanks to its strong adhesive properties, flexibility, and water resistance. This comprehensive guide will walk through each step of how to correctly apply mastic when adding a backsplash. With the right tools and techniques, you can achieve a seamless, long-lasting backsplash that enhances your kitchen.

Benefits of Using Mastic for Backsplashes

Mastic adhesive offers several advantages that make it well-suited for backsplash installation:

  • Strong adhesion: Mastic bonds tightly to most common backsplash materials and provides a permanent, water-resistant hold. This prevents tiles or panels from slipping over time.
  • Flexibility: As a latex-based adhesive, mastic retains some flexibility after drying. This allows the backsplash to expand and contract with temperature changes and natural movements of the wall without cracking.
  • Water resistance: Mastic resists water penetration far better than standard adhesives. This is essential for backsplashes which can be exposed to splashes and steam daily.
  • Easy to apply: Mastic spreads smoothly and easily with a trowel. It is also more forgiving than thinset during application.
  • Easy cleanup: Excess wet mastic can be cleaned with water before drying. It doesn’t dry as quickly as thinset, allowing more working time.

With proper installation, a backsplash adhered with mastic can last for decades without any loosening or damage from moisture. Now let’s look at how to apply it correctly.

Choosing the Right Mastic

Not all mastics are suitable for backsplash installation. It’s important to choose one designed for tile or glass and intended for kitchen use. Look for key specifications:

Water Resistance

Since the backsplash will be exposed to water, choose a mastic adhesive that specifically says “water resistant” or “for wet areas”. Avoid general purpose mastics.


Backsplashes require an adhesive with some flexibility after drying to prevent cracking. Ensure the mastic states “flexible” on the label.

Mold Resistance

To prevent mold growth in the humid kitchen environment, select a mastic that contains mold inhibiting properties.

Non-sag Qualities

The mastic must be thick enough not to slump when applied to a vertical surface. Look for mastics labeled “non-sag”.

With a mastic designed for kitchen backsplash installation, you can be confident it will provide a water-resistant bond for the long term.

Preparing the Surface

Just as important as choosing the right mastic is proper wall preparation. Taking time to ready the installation area will allow the mastic to adhere optimally.


The wall should be clear of any dirt, grease, or soap residue that could impair adhesion. Wash the entire backsplash area with a degreasing cleaner and allow to fully dry.

Structural Repairs

Inspect the wall and make any necessary repairs to holes, cracks, or uneven sections. Fill gaps with spackle or caulk and sand smooth. The mastic will only be as strong as the wall underneath.


Most backsplash materials like tile and metal don’t require wall priming. However, painting a coat of primer helps seal porous drywall and improves mastic bond strength. Use a PVA drywall primer for best results.


Map out the planned placement of your backsplash. Measure and mark where the top and bottom rows will sit and make a level line to follow. Having this layout done ahead of time will make applying the mastic much easier.

With clean, flat, and dry walls, you can move on to mastic application confident the backsplash will adhere as intended.

Applying the Mastic

Spreading the mastic evenly across the wall area is key for proper backsplash bonding. Follow these best practices during application:

Use a Notched Trowel

A notched trowel allows you to control the thickness and coverage of the mastic applied. Choose a trowel sized for your tile or panels with notches of 1/8” for maximum contact.

Apply in Small Sections

Only apply mastic to areas that can be covered before a skin forms on the surface. Work in 2-3 square foot sections.

Spread Evenly

Use the trowel’s flat side to first apply a thin base layer. Then go back over with the notched side in straight lines to create uniform ridges.

Observe Coverage Rates

Consult the mastic packaging for the recommended coverage in square feet per gallon. Staying within this rate will ensure you apply the proper adhesive thickness.

Work to Layout Lines

Spread mastic right up to your top and bottom layout lines. This will make aligning the backsplash much simpler.

Let Cure Slightly

Give the mastic 5-10 minutes to skin over slightly before placing tiles or panels. The tackiness will help hold the pieces in place.

Applying mastic in controlled sections will keep the adhesive within its working time. Now let’s review how to handle the backsplash materials.

Setting the Backsplash Pieces

With the mastic in place on the wall, carefully install the backsplash while following a few guidelines:

Work from the Bottom

Begin setting pieces starting from the bottom row. Let gravity keep them in place as you work upwards.

Press and Twist

As you set each tile or panel, press it into the mastic and twist slightly to flatten ridges and improve contact.

Check Alignment

Periodically step back and check alignment to your layout lines to ensure even spacing.

Watch for Slippage

If pieces start to slide downward, the mastic has skinned over too much. Remove and reapply fresh mastic in this area.

Clean Excess

As you work, use a damp sponge to wipe up any mastic that squeezes out between pieces before it dries.

Leave Gap for Grout

Don’t butt tiles or panels tightly. Leave a 1/16” gap between each for grouting after they are set.

Take care during installation to keep all pieces aligned and fully embedded into the mastic. Avoid walking or leaning on the backsplash until the mastic has cured 24 hours.

Grouting and Finishing the Backsplash

Once the mastic has fully dried,there are just a few remaining steps:

Apply Grout

Mix up grout in a matching color to your backsplash material and work it into the seams using a grout float. Let dry completely.

Caulk Perimeter

Run a flexible silicone caulk along the top and side gaps between the backsplash and wall. This allows for expansion and seals the edges.

Seal if Needed

If your backsplash requires sealing, apply the appropriate sealer evenly across the entire surface. Check the product specifications.

And that completes the installation! With proper mastic application techniques, your new backsplash will provide beauty and function in your kitchen for many years.

Frequently Asked Questions About Applying Mastic for a Backsplash

What kind of mastic is best for kitchen backsplash installation?

Look for mastic that is labeled as water-resistant, flexible, non-sagging, and mold-resistant. These properties provide the right adherence and moisture protection needed behind a sink or stove.

How long does mastic take to dry before applying backsplash?

Mastic adhesives designed for backsplash installation take about 5-10 minutes to form a tacky skin. This allows time to spread mastic before the tiles need to be applied and prevents excessive slippage.

Should I use mastic or thinset for a backsplash?

Mastic is preferred over thinset for typical backsplash areas that are not excessively hot or heavy. Mastic bonds well, allows more working time, and its flexibility resists cracking. Thinset dries quicker and can be more difficult for DIY installation.

Can I apply mastic directly over drywall for a backsplash?

In most cases, mastic can be spread directly onto drywall that is cleaned and primed. Its adhesion and flexibility allow it to bond well even on slightly uneven, porous surfaces. This avoids the extra steps of installing backerboard.

Is mastic waterproof when dry?

While mastic is water-resistant, no adhesive is 100% waterproof. Using a quality kitchen-grade mastic provides excellent resistance to moisture and steam from typical backsplash exposure. But excessive or prolonged wetness can still seep through over time.

How long will a backsplash installed with mastic last?

With proper wall preparation and application technique, a quality mastic will securely hold a backsplash for decades without issue. Mastic forms a permanent bond to surfaces when fully cured, while retaining flexibility to handle temperature changes and natural movement.

Can I change the color of my mastic if I don’t like the original color?

Yes, mastic adhesives can be tinted to any color by mixing in universal colorants. Add a few drops at a time and thoroughly blend until the desired color is reached. Just be sure to keep the ratio below 10% colorant to maintain the mastic properties.


Installing a kitchen backsplash with mastic adhesive allows you to enhance your space with beautiful, functional tiles or panels that will stand up to daily use. With the ability to strongly yet flexibly bond materials even on imperfect walls, mastic is an ideal option for the DIYer. Choosing the right mastic formulation and properly preparing surfaces prior to application is key, as is careful spreading techniques. Follow the steps covered here during your next backsplash project, and you can expect many years of enjoyment from your customized backsplash.