How to Apply Mortar for Tile Backsplash

Installing a tile backsplash can transform the look of your kitchen or bathroom. With the right materials and techniques, you can create a stylish, durable backsplash that will last for years. A critical step is properly applying the mortar that adheres the tiles to the wall. Here is a detailed guide on how to apply mortar for a tile backsplash.


Mortar acts as the “glue” that bonds the tile to the wall surface. Using the right type of mortar and applying it correctly ensures a strong, lasting bond between the tile and wall. This prevents tiles from loosening or falling off over time.

When installing a tile backsplash, a polymer-modified thinset mortar is generally recommended. Thinset contains a polymer additive that makes it stronger and more flexible than regular mortar. This allows it to better handle the expansion and contraction that occurs with temperature changes. Backsplashes also require a thin layer of mortar, hence the name “thinset.”

Proper mortar application involves spreading an even, uniform layer onto the wall and back of each tile. The mortar must fully coat the surfaces to create maximum contact and adhesion. Careful installation techniques are needed to accomplish this crucial step.

This guide will walk through the entire process covering the key points of how to properly apply mortar when installing a tile backsplash:

Choose the Right Mortar

  • For backsplashes, use a polymer-modified thinset mortar. Avoid mastic or regular mortar which are not ideal for tiles.
  • Pick a thinset mortar recommended for wall installations and your type of tiles – porcelain, ceramic, glass, etc. Consult manufacturer guidelines.
  • Mortar with a built-in adhesive polymer provides stronger bonding power.
  • White thinset mortar is useful for glass or translucent stone tiles. For other tiles, gray mortar is fine.
  • Mortar modified with latex or acrylic polymers offer enhanced flexibility and adhesion.
  • Pre-mixed thinset mortars allow for quick, easy application. Powdered mortars require mixing with water first.

Prepare the Surface

  • The wall surface must be clean, dry, and structurally sound before applying mortar.
  • Repair any cracks or holes and remove loose paint or wall coverings.
  • Painted surfaces should be lightly sanded to roughen up the area for better mortar adhesion.
  • For highly absorbent surfaces like drywall, apply a primer coat so the mortar doesn’t dry out too quickly.
  • Remove any dust or debris before starting. The surface should be as smooth as possible.

Mix the Mortar

  • For pre-mixed thinset mortars, no mixing is required. Simply stir it up before use.
  • For powdered mortar, mix it with clean water in a bucket. Follow package directions for mix ratio.
  • Mix to a smooth, lump-free consistency – not too thick or runny. Allow mixture to slake for 5-10 minutes.
  • Re-stir occasionally as you work to maintain proper consistency. Avoid re-tempering with water as this weakens it.
  • Only mix up what you’ll use in 30-60 minutes. Mortar dries quickly once mixed.

Spread the Mortar

  • Use a notched trowel to spread the mortar evenly across the surface area.
  • Apply a skim coat first to fill in any voids or gaps if needed.
  • Hold trowel at 45° angle and apply an even 1/4″ layer using horizontal strokes.
  • Immediately follow with more strokes held at a 90° angle to create a ridged pattern.
  • Spread only as much mortar as can be tiled in 30 minutes before it skins over.
  • Back-butter each tile by applying a thin layer of mortar to the back using the flat side of the trowel.

Set the Tiles

  • Firmly press tiles into the ridged mortar within 10-15 minutes of spreading.
  • Push in a direction perpendicular to the trowel lines to collapse the ridges.
  • Twist tiles back and forth slightly to flatten ridges and promote maximum adhesion.
  • Use spacers between tiles to achieve consistent grout joint spacing.
  • Periodically remove and check tiles to ensure 100% mortar coverage on back.
  • Strike joints and remove excess mortar once tiles are set. Allow drying for 24 hours before grouting.

Tips for Success

  • Maintain a workable consistency by re-stirring mortar regularly as you go.
  • Work in small sections so mortar doesn’t dry out before tiles are set.
  • Ensure tiles are fully embedded by twisting and pushing perpendicularly to ridges.
  • Use tile spacers for consistent spacing and proper alignment.
  • Allow 24 hours for mortar to cure before grouting. Wait 48-72 hours before using shower or exposing to heavy use.
  • Clean tools and hands periodically while working to remove accumulated mortar before it dries.

Common Questions

How long does mortar for backsplash take to dry?

Thinset mortar takes 24 hours to initially set and cure before grouting. Full drying and maximum strength take 72 hours. Avoid heavy use of the backsplash until fully cured.

Does backsplash mortar need to be sealed?

No, thinset mortar bonds directly to the tiles and does not require sealing. The grout between the tiles will need to be sealed after installation.

What’s the ratio for mixing thinset mortar?

Powdered thinset mortar is typically mixed with water at a ratio of 2.5 to 3 parts powder to 1 part water by volume. Always follow package directions.

Can regular mortar be used for backsplash instead of thinset?

No, regular mortar is not ideal for backsplashes. Thinset mortar has polymers that improve adhesion and flexibility, both important for tiles.

How long is bagged thinset mortar good for after mixing?

Once mixed, thinset mortar is workable for 2-3 hours max. Mortar will begin hardening after this time, making tile adhesion poor.


Applying mortar is a crucial step in installing a tile backsplash. With the right thinset mortar and proper application techniques, you can achieve excellent adhesion for a long-lasting, quality finished product. Pay close attention to fully embedding tiles in the mortar using adequate pressure and twist-setting motions. Allowing adequate drying time for the mortar to cure properly also ensures your new backsplash will stay securely bonded to the wall for many years.