What Size Trowel for Mosaic Backsplash

Selecting the right trowel size is an important decision when installing a mosaic tile backsplash. The trowel determines how much thinset mortar is applied to the wall, which affects adhesion and proper coverage of the tile. This article will examine the factors to consider when choosing a trowel for mosaic tile, and provide recommendations for common backsplash installations.


A trowel is a hand tool used to apply thinset mortar or adhesive when installing tile. The notched edge of the trowel creates ridges that allow the thinset to be spread evenly at a consistent depth. The size and spacing of the notches determine how much material is applied with each pass of the trowel.

For small mosaic tiles, a smaller notched trowel is needed to ensure proper coverage without leaving gaps or voids in the thinset. Using the right trowel size for the tile and application is key to achieving a long-lasting, high quality installation.

When installing a mosaic backsplash, these are the main factors to consider when selecting a trowel:

  • Tile size – Smaller tiles require a smaller notched trowel size. Mosaics are generally 1 inch or smaller.
  • Tile material – Natural stone mosaics require a deeper thinset bed than ceramic or glass tile.
  • Surface material – The texture and absorbency of the surface being tiled determines how much mortar is needed.
  • Mosaic mounting – PAPER-FACE mounted mosaics require a smaller trowel notch than mesh-backed mosaics.
  • Backsplash size – The area being tiled impacts the trowel selection. A larger backsplash may require a larger trowel.

With these factors in mind, we can determine the best trowel size and type for a mosaic backsplash installation.

Recommended Trowel Sizes for Mosaic Backsplashes

Ceramic or Glass Mosaic Backsplash on Drywall

For a standard 12×12 inch ceramic or glass mosaic backsplash on drywall, a 1/4 x 3/16 notch trowel is recommended. The 1/4 inch deep notches will apply enough thinset to achieve full coverage of each tesserae when beat into the tile.

A variation is the 1/4 x 1/4 inch square notch trowel, which also provides suitable coverage for most wall applications with ceramic mosaics. The square notches allow for efficient application of the mortar.

Natural Stone Mosaic Backsplash

Due to the depth and irregularities on the back of each piece, natural stone mosaics require a deeper layer of thinset. For common natural stone types like marble, granite, or travertine, use a 1/4 x 1/4 x 1/4 notch trowel.

The 1/4 inch square notches provide adequate thickness for the mosaic tiles to be fully embedded. This helps prevent cracking or dislodging of the stone pieces over time.

Large Format Mosaic Backsplash

For mosaics with pieces larger than 1 inch, or for a floor-to-ceiling backsplash installation, a 1/4 x 1/4 x 3/8 notch trowel is ideal. The deeper notches provide additional thinset to properly adhere the larger tiles and accommodate any unevenness in the surface.

Mesh-Backed Mosaic Sheets

For mosaic tiles mounted on a mesh backing, use a 3/16 x 5/32 V-notch trowel. The v-notches help spread the mortar evenly across the mesh, fully covering each tesserae. The thickness of the notches is suitable for the mesh depth.

Small Mosaic Accents or Borders

For adding a mosaic border or accent strip on the backsplash, a smaller 1/8 x 1/8 notch or 3/16 x 3/16 notch trowel can be used. The reduced thickness ensures the mosaic pieces don’t slide on too thick of a mortar bed.

Trowel Size Recommendations

Here is a summary of recommended trowel sizes for common mosaic backsplash installations:

  • Ceramic/glass on drywall – 1/4 x 3/16 notch or 1/4 x 1/4 notch
  • Natural stone – 1/4 x 1/4 x 1/4 notch
  • Large format mosaics – 1/4 x 1/4 x 3/8 notch
  • Mesh mounted – 3/16 x 5/32 V-notch
  • Borders/accents – 1/8 x 1/8 notch or 3/16 x 3/16 notch

Factors That Impact Trowel Size

While the above recommendations cover most standard backsplash installations, there are some additional factors that can impact the trowel size needed:

  • Irregular substrate – Surfaces like concrete block or brick may require a deeper trowel notch to account for unevenness.
  • Professional standards – Building codes or professional associations may dictate specific trowel sizes for certain applications.
  • Manufacturer specifications – The tile or setting material manufacturer may recommend a specific trowel type. Always check their guidelines.
  • Personal preference – Some installers prefer deeper notches even on smooth surfaces to provide additional mortar contact.

Proper Use of the Trowel

Once the right trowel is selected, proper technique is crucial to get an ideal mortar coverage:

  • Hold the trowel at a consistent 45-60° angle to the surface.
  • Apply even pressure to get uniform ridges.
  • Use a sweeping arc motion to efficiently cover the area.
  • Apply only as much mortar as can be covered with tile before it skins over.
  • After beat in, check for 100% coverage with no voids before applying tile.
  • Use the flat side of the trowel to scrape any excess mortar from the joints.


Choosing and using the right sized trowel makes a big difference in achieving a successful mosaic tile backsplash installation. Consider the tile size and type, substrate, application area, and professional recommendations when selecting a trowel. Proper technique also ensures you get the right mortar coverage. With the guidelines provided in this article, you can determine and apply the ideal trowel for your next mosaic backsplash project.

FAQ about Trowel Size for Mosaic Backsplash

What size trowel is best for a standard subway tile backsplash?

For typical 3×6 inch ceramic subway tiles on a drywall backsplash, a 1/4 x 3/8 notch trowel is recommended. The wider notches provide enough thinset for proper coverage under the large format tiles.

Should I use a fine tooth comb when installing mosaic sheets?

Yes, using a notched trowel followed by a fine tooth tile comb helps work the mortar evenly through the mesh backing on mosaic tile sheets. The comb ensures thinset contact with each tesserae.

How do I know if my trowel size is too big or small for the tile?

A trowel too small for the tile will not provide full mortar contact, while one too large can cause excess thinset to squeeze up into the joints. Proper trowel size will fully embed tiles without overspreading the adhesive.

Can I use the same trowel for the walls and floor?

It’s recommended to use a larger trowel for floor installations. A 1/4 x 3/8 inch trowel is suitable for walls, while a 1/2 x 1/2 inch works better for floors in most cases.

What trowel notch is best for large format tiles?

For tiles 15 inches or larger on any one side, a 3/4 x 9/16 inch U-notched trowel is typically recommended to provide maximum mortar contact and account for tile warpage.

How important is cleaning trowel notches while tiling?

Keeping trowel notches clean of thinset residue during installation helps maintain the proper ridge height for even adhesive coverage with each trowel pass.

Key Takeaways

  • Select a trowel size based on tile size/type, substrate, area, and professional recommendations.
  • For most mosaic backsplashes, a 1/4 x 3/16 notch or 1/4 x 1/4 notch trowel is suitable.
  • Natural stone mosaics require a deeper notch ~1/4 inch to support irregular pieces.
  • Hold the trowel at a consistent angle and use sweeping arcs for even coverage.
  • Properly cleaning trowel notches is key to maintaining proper mortar application.