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Trowel Guidelines

PROPER USE OF TROWELS AND OTHER IMPORTANT INFORMATION: 1. Always check trowel for excessive wear before using.

ADHESIVES

DRY-SET MORTARS

4-1/4” wall tile and ceramic mosaics on masonry and concrete:

4-1/4” wall tile and ceramic mosaics on dry wall:

2. Use the flat side of the trowel to key mortar or adhesive into sub strate to achieve the best possible mechanical bond.

1/4” x 1/4” x 5/16”

3/16” x 5/32”

1/4”

1/4”

3/16”

3. Comb in one direction with the notched side of the trowel, holding it at a 45 degree angle. Specifications require no less than 3/32 in. (2mm) mortar and 1/32 in. (1mm) adhesive between tile and sub strate after proper bedding.

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5/16”

5/32”

6” x 6” to 9” x 9” on masonry walls or concrete:

6” x 6” to 9” x 9” on dry wall:

4. Set tile with a sliding motion perpendicular to the mortar ridges.

1/4” x 1/4” x 3/8”

1/4” x 1/4” x 1/4”

5. The 80-95% coverage shall be sufficiently distributed to give full support to the tile with particular attention to this support under all corners and edges of the tile. 6. Installer must periodically remove sheets or individual tiles to assure proper bond coverage consistent with industry specifica tions. Lack of adequate coverage may be due to improper bedding of the tile, inconsistent angle of the trowel during application, or use of a worn trowel.

1/4”

1/4”

1/4”

1/4”

1/4”

3/8”

12” x 12” and larger on masonry walls, concrete and dry wall:

1/4” x 1/4” x 1/2”

1/4”

1/4”

7. Button back, lugged or key-back tiles require special attention. See notes below.

1/2”

LHT MORTARS

Notes: 1. “Proper Bedding Procedures” is located on page 190. 2. Large and Heavy Tile Mortar (LHT Mortar) information is located on page 206. 3. Dry-set mortars include dry set and latex modified mortars. 4. Box screed, recommended for 12 in. x 12 in. (305 mm x 305 mm) and larger tiles.

12” x 12” and larger size tiles on masonry or concrete, tiles with thickness variation:

25/64” x 3/4” x 19/32”

3/8” x 3/4” x 9/16”

25/64”

3/4”

3/8” 3/4”

19/32”

9/16”

NOTE: Trowel diagrams not drawn to scale.

IMPORTANT NOTICE: These guidelines cannot address every installation circumstance. The substrate, type and size of tile, intended service level of the installation, climatic conditions, interior or exterior use, and individual manufacturer’s recom mendations are all factors the installer should consider in selecting the proper trowel.

NTCA Reference Manual | 2024 / 2025

Chapter 8 | Thin-Bed Method Installations

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