How to Apply Mortar for Backsplash


Installing a backsplash in your kitchen or bathroom can add style, protect your walls from splatters and spills, and give you a surface that’s easy to clean. While backsplashes can be made from different materials like tile or metal sheets, applying mortar as the adhesive is a crucial step for a long-lasting, quality installation.

Properly preparing the surface and applying the mortar takes precision and patience but is something a motivated DIYer can tackle. This guide will walk you through all the key steps for how to apply mortar for backsplash installation.

Gather the Right Mortar and Tools


  • Use premixed thin-set mortar designed for walls and backsplashes. This type contains polymers that make it stronger and more flexible.
  • Make sure the mortar is suitable for the backsplash material you’re using like tile, stone, or glass.
  • Buy the right amount of thin-set mortar based on the size of your project. Having too little can lead to a poor bond while excess will be wasted.


  • Trowel – Use a notched trowel with a thickness that matches the backsplash material.
  • Mixing bucket, paddle, and drill – To mix the thin-set mortar evenly before use.
  • Grout float – For smoothing the mortar evenly on the wall.
  • Spacers – Small plastic crosses used between tiles to create even grout lines.
  • Grout sealer – To protect finished grout lines from stains.

Prep the Wall Surface

Proper prep work is crucial for the mortar to adhere correctly to the wall.

  • Make sure the wall is clean and dry first. Remove any loose paint, wallpaper, grease, or soap scum.
  • Fill any holes or uneven areas in the wall with spackle so the area is smooth.
  • Prime the wall if needed so the mortar bonds well.
  • Mark the wall with a level to ensure your backsplash will be installed straight.

Mix and Apply the Mortar

  • Pour the dry mortar into a bucket and gradually add water while mixing with a drill paddle.
  • Mix to a thick, pasty consistency according to the product directions. The mortar should hold its shape when spread on the wall.
  • Spread a thin layer of mortar over a small section of the wall area, using the notched side of the trowel.
  • Use the flat side of the trowel to smooth and evenly spread the mortar.
  • Only cover an area that can be tiled before the mortar dries, usually only a few square feet at a time.

Set and Grout the Backsplash Tiles

  • Press the backsplash tiles firmly into the mortar, using spacers between the tiles for even grout lines.
  • Ensure the tiles are aligned and level as you place them. Adjust as needed.
  • Allow the mortar to fully cure for 24-48 hours before grouting according to manufacturer directions.
  • Mix the grout and apply it over the tiles to fill the grout lines.
  • Wipe away excess grout with a damp sponge and allow it to dry.
  • Seal and protect the grout lines with grout sealer once fully dry.

FAQs About Applying Mortar for Backsplashes

How thick should I apply mortar on the wall?

Apply a layer of mortar about 1/8 to 1/4 inches thick. The notched trowel teeth should leave enough thickness for your tile or backsplash material.

What’s the best mortar for a backsplash?

Use a polymer-modified thin-set mortar made specifically for walls and backsplashes. Avoid mastic adhesive or multi-purpose compounds.

Do I need to seal the mortar after it dries?

Sealing is not necessary for mortar behind a backsplash. But you should seal the grout lines once installed to prevent staining and damage.

Can I apply mortar directly over drywall or plaster?

Yes, mortar can be applied over drywall or plaster. Make sure to prep the surface correctly so it is clean, dry, and primed first.

How long does mortar take to dry before grouting?

Most thin-set mortars take 24-48 hours to fully cure before grouting. Check the product directions for recommended cure times.


Applying mortar is an essential part of securing backsplash tiles or panels properly on your wall long-term. While it requires careful prep and precise technique, take your time and follow this guide for how to apply mortar for backsplash projects. With the right materials and methods, you can achieve a beautiful, high-quality finished backsplash.