How Much Mastic for Backsplash – A Complete Guide

Installing a beautiful backsplash in your kitchen or bathroom can really take the design to the next level. However, getting those backsplash tiles properly secured to the wall takes a bit of mastery. Using the right amount of mastic adhesive is key for creating a long-lasting backsplash installation. Read on to get a fully detailed guide on how much mastic you need for backsplash projects of any size.

What is Mastic?

Before calculating how much adhesive you need, it’s important to understand what mastic is and why it’s the best choice for backsplash installations.

Mastic is a versatile tile adhesive that comes in premixed tubs or tubes. It has a smooth, toothpaste-like consistency that is easy to spread onto surfaces with a trowel or putty knife. Mastic contains vinyl polymers and fillers that allow it to strongly bond surfaces together.

Here are some of the key benefits of using mastic for backsplash projects:

  • Strong Adhesion – Mastic bonds tightly to most common backsplash materials including tile, glass, metal, and stone. It helps create a long-lasting connection.
  • Waterproof – Mastic is water-resistant and helps protect against moisture damage. This makes it suitable for wet areas like kitchens and bathrooms.
  • Flexible – Mastic can flex and move with the backsplash over time without cracking or letting go. This prevents tiles from popping off.
  • Easy to Use – Premixed mastic spreads smoothly and easily. It is beginner-friendly compared to mortar or thinset.
  • Fast Drying – Mastic dries relatively quickly, allowing you to grout faster compared to other adhesives.

For most backsplash projects, mastic is the simplest, most effective adhesive to use. Next you need to determine precisely how much mastic you’ll require.

Factors That Determine How Much Mastic You Need

Mastic coverage depends on several factors relating to your specific backsplash project:

Size of the Backsplash Area

The overall size of the surface being tiled is the biggest determinant of how much mastic is required. Large backsplashes require more adhesive than small accent areas. Measure the height and width of your backsplash installation area in square feet to estimate needed mastic.

Tile Size

The dimensions of your individual backsplash tiles also impacts mastic needs. Small mosaic tiles require more adhesive per square foot than larger subway tiles. Factor in your tile size.

Tile Material

Certain backsplash materials like glass tile have slightly different mastic requirements than ceramic or stone. Check if your tile choice needs more or less adhesive.

Trowel Notch Size

The size of the trowel’s notches determines how much mastic it dispenses per tile. Bigger notches release more adhesive. Choose the right trowel for your tile type.

Surface Material

Rough or porous backsplash surfaces like plaster or concrete may soak up more mastic than smoother drywall or plywood. Consider what you’re tiling over.

Tile Layout

Intricate tile patterns deviate from straight layouts which alter the spread rate. Fancy designs use more adhesive than basic grids.

Now that you know the key factors that influence mastic needs, here is how to accurately calculate the right amount for your next backsplash installation.

How to Calculate Exact Mastic Needs

Figuring out precisely how much mastic adhesive you need for a backsplash comes down to a simple area calculation combined with the manufacturer’s coverage specifications. Follow these steps:

1. Measure Backsplash Area

  • Use a tape measure to measure the height and width of the backsplash installation area.
  • Multiply the height x width to calculate the area in square feet.
  • For irregular shaped spaces, break the area into separate rectangles to determine square footage.

2. Check Manufacturers Recommended Coverage

  • The mastic packaging or product datasheet lists the standard coverage in square feet per gallon or tube.
  • This varies by brand from around 20-50 sq ft per gallon.
  • Consider factors like tile size and absorbency of the surface material to determine if you’ll need more or less than the recommended coverage.

3. Calculate Mastic Needed

  • Take your backsplash area and divide it by the manufacturer’s coverage.
  • This tells you exactly how many gallons or tubes of mastic are required for the project.
  • Round up to the nearest full container to ensure you purchase enough.

Following this simple calculation will provide an accurate estimate of mastic needs for any backsplash. Let’s look at two examples.

Example 1: Small Backsplash

For a small backsplash that is 3 feet high x 2 feet wide = 6 sq ft area.

The mastic specs 35 sq ft per gallon recommended coverage.

6 sq ft divided by 35 sq ft per gallon = 0.17 gallons needed. Round up to 1 gallon.

Example 2: Large Backsplash

For a larger backsplash 8 feet high x 5 feet wide = 40 sq ft area.

The mastic specs 20 sq ft per gallon recommended coverage.

40 sq ft divided by 20 sq ft per gallon = 2 gallons needed.

Use this same process to determine how many tubes of mastic you’ll need for mosaics or small backsplash projects.

Now that you can accurately calculate the right amount of adhesive, let’s look at how to properly apply mastic.

Applying Mastic Properly

With the right amount of mastic on hand for your backsplash, the key is spreading it effectively to ensure a successful installation. Follow these best practices:

Choose the Right Trowel

  • Select a trowel where the notch size matches the tile dimensions.
  • Large tiles require bigger notches, small mosaics need smaller trowel teeth.
  • This ensures you apply the proper amount of mastic for full coverage under each tile.

Spread Evenly Over the Surface

  • Apply a smooth, even layer of mastic over the backsplash area using the trowel.
  • Spread it in straight rows at a 45 degree angle from the previous row.
  • Cover only as much area as you can tile over before the mastic skins over.

Use the Proper Thickness

  • Maintain the adhesive layer at the depth of the trowel notches.
  • Avoid using too little mastic which leads to poor adhesion.
  • Also avoid applying mastic too thickly which can cause tiles to slide.

Work in Sections

  • Divide the backsplash into sections of a few square feet to Control mastic area.
  • This prevents it from drying out before tiles are applied.
  • Reapply fresh mastic as you move to new sections.

Follow these application tips along with the mastic amount calculation, and you can install any backsplash like a pro.

Common Mastic Adhesive Types

Now that you know how much mastic you need and how to apply it, let’s examine the common adhesive types available:

Premixed Acrylic-Latex Mastic

  • All-purpose mastic for most indoor backsplash projects.
  • Simple water clean-up formula bonds well to common materials.
  • Ideal balance of strength and ease of use.

Epoxy Mastic

  • Two-part mastic that creates an extremely strong, permanent bond.
  • Useful for heavy backsplashes like stone or outdoor installations.
  • More difficult to work with than premixed mastic.

Mortar Mastic

  • Contains mortar cement for added durability and strength.
  • Less flexible than acrylic mastic making it prone to cracking.
  • Typically used for floors but sometimes backsplashes.

Organic Adhesive Mastic

  • All-natural plant-based formula for green projects.
  • Lower strength limits use to lighter backsplash tiles.
  • Safe for environmentally-concerned DIYers.

For most standard backsplash installations, a quality acrylic-latex mastic adhesive is recommended. Always check that the product is suitable for the backsplash material and location.

Tips for Measuring Mastic Needs

Here are some additional tips to keep in mind when estimating how much mastic is required:

  • For backsplashes over 50 square feet, purchase 10-20% extra mastic. It’s easier to return unopened containers than run short mid-project.
  • Consider buying extra mastic if tiling over rough surfaces that tend to soak it up quickly.
  • Be prepared to use more mastic than the coverage rates state when installing glass tiles or mosaics. The slick surfaces often require additional adhesive.
  • Let the size and thickness of the notched trowel determine spread rate, not trying to eyeball the right amount. Consistent depth is key.
  • Consider purchasing a mastic tube system for squeezing out the ideal amount if working with mosaics. This prevents waste.
  • Check mastic packaging for the recommended tile size ranges to make sure product is suitable for your backsplash tiles.

Buying the proper amount of quality mastic adhesive takes the guesswork and frustration out of installing an beautiful backsplash. Use this guide to determine how much you need for a seamless project.

Frequently Asked Questions About Mastic for Backsplash Projects

Here are answers to some of the most common questions homeowners have about calculating and using mastic adhesive for backsplash installations:

How long does mastic take to dry before applying tiles?

Most mastic takes 15-30 minutes to become tacky and ready for tiles to be applied. Check packaging as drying times vary by brand.

Does mastic expire if leftovers are saved?

Unopened mastic has a shelf life around 2 years. Opened containers expire faster once exposed to air. Tightly reseal and store in a cool, dry place.

Is mastic waterproof once fully cured?

Quality mastic becomes water-resistant after drying 24-48 hours. Epoxy formulas offer the most waterproofing. Avoid excessive moisture until fully set.

Can excess mastic be scraped off after drying?

Dried mastic can be very difficult to remove from tile and tools. Wipe up excess immediately before it dries using a damp sponge or towel.

Is mastic better than thinset mortar for backsplashes?

Mastic generally bonds better than thinset on vertical backsplashes. Thinset remains thicker and is more prone to sliding off walls before drying.

How should mastic be stored?

Keep mastic containers tightly sealed in a dry area between 50-80°F. Avoid temperature extremes. Do not freeze mastic or store with direct sun exposure.

Can mastic be used outdoors?

Standard mastic should not be used in outdoor installations subject to weather. Use a exterior-grade epoxy or mortar adhesive for outdoor backsplashes.

Does backsplash material affect mastic choice?

Certain materials like metal or glass may require a more flexible mastic or primer coat. Always check that the adhesive suits the backsplash tile type.

How soon can backsplash grout be applied after installing tiles?

Mastic drying times range 2-8 hours before grouting can begin. Actual time depends on ambient temperature and humidity. Check packaging for recommended grout times.

Using the proper amount of quality mastic adhesive paired with great tiling technique allows you to create durable, beautiful backsplash designs. Refer to this guide anytime you need to know precisely how much mastic is required for upcoming projects. Happy tiling!


Installing a backsplash can take your kitchen or bathroom from basic to beautiful. With a stunning selection of tiles now available in endless styles, the design options are limitless. The key is properly executing the installation, especially getting the adhesive right.

Determining exactly how much mastic you need for a backsplash comes down to measuring the area and factoring in the manufacturer’s coverage rates. Carefully apply the mastic with the recommended trowel and technique. Consider the characteristics of the tile material and backsplash location in choosing the ideal adhesive product.

With the detailed information in this guide, you can now confidently calculate and apply the perfect amount of mastic. Doing the prep work upfront ensures you have sufficient adhesive to prevent problems down the line. Take the time to spread it evenly in proper sized sections. Follow the tips provided here and you can achieve a backsplash installation you’ll be proud to show off for years to come.