2024-25_NTCA_Reference_Manual_dig_dwnld

Proper Preparation and ANSI Requirements for Thin-Set Method Tile Installation

Drywall

Concrete Slabs

Masonry Walls

1. Do not apply curing compounds or topical sealers to concrete slabs receiving thin-set method tile installations.

1. Erect walls with correct angles, straight, square and plumb to within 1/4 in. in 10 ft. (6 mm in 3 m) and no more than 1/16 in. per 12 in. (2 mm in 305 mm) variation from the required plane. For tiles with at least one edge 15 in. (0.38 m) or larger, 1/8 in. in 10 ft. (3 mm in 3 m) and no more than 1/16 in. in 24 in. (2 mm in 610 mm) variation from the required plane. Failure to provide walls according to these standards cannot be corrected by a thin-set. Thinset mortar is not intended to be used to true or level substrates.

1. Erect stud walls with correct angles, straight, square and plumb with stud faces forming a flat plane. Interior angles or changes in plane shall be framed or blacked to provide solid backing for interior corners. For tiles with at least one edge 15 in. (0.38 m) or larger, 1/8 in. in 10 ft. (3 mm in 3 m) and no more than 1/16 in. in 24 in (2 mm in 610 mm) variation from the required plane. Failure to provide walls according to these standards will require preparation prior to installation of materials. Thinset mortar is not intended to be used to true or level substrates. Out of tolerance walls cannot be corrected by thinset mortar. 2. Tape all joints and eliminate voids. In wet areas, use water alkali-resistant tape. 5. Install drywall 1/4 in. (6 mm) above the floor and where the vertical surface intersects with horizontal surfaces, such as tub rims. 6. Unprotected gypsum drywall is not a recommended substrate for thin-set tile installations in wet areas. 7. Caution: when metal straps are installed over studs, in lieu of between studs to provide support for wall hung fixtures, grab bars, etc., shimming the remainder of the studs the same thickness as the supports and screws is required prior to installing dry wall to provide a suitable substrate to cover with tile. 3. Eliminate corner beads from out corners that are to be wrapped with tile. 4. Square inside and outside corners.

2. Protect concrete slabs from oil, grease, and other contaminants.

3. Some job-site heaters and portable fuel heaters may emit contaminants that may be detrimental to direct mortar bond installations on concrete. 4. Trowel slabs and then give a light broom finish to achieve the best bond of the thin set mortar to the slab. Highly polished or mechanically finished slabs may not be conducive to mortar adhesion. 5. Maximum permissible variation 1/4 in. in 10 ft. (6 mm in 3 m) with no more than 1/16 in. per 12 in. (2 mm in 305 mm) variation from the required plane, except as required for drainage. For tiles with at least one edge 15 in. (0.38 m) or larger, 1/8 in. in 10 ft. (3 mm in 3 m) with no more than 1/16 in. per 24 in. (2 mm in 610 mm) variation from the required plane. 6. If the floor is expected to drain, the slab shall be placed with the appropriate pitch for the specified tile material. 7. If the drains are not adjustable, set the drains above the slab to accommodate the specified tile and setting material. Do not pack an adjustable drain weep with mortar or other solid material. Consider using a manufactured drain assembly. For thicker tile or paver material, seek the advice of a qualified tile contractor. 8. It is the responsibility of the owner, project designer or architect to specify and locate control joints. Give careful attention to the plans, specification requirements, and locations for all expansion joints, control joints, and cold pour joints. Required joints should be on straight lines and exact angles that will conform to the tile joint location.

2. Strike joints flush and prepare the same as if they were to be painted.

3. Erect inside and outside corners square and free of excess mortar.

4. Block filler or paint shall not be used on surfaces to receive tile.

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NTCA Reference Manual | 2024 / 2025

Chapter 2 | Substrates