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Concrete Flatness and Level

Problem

Cause

Cure

Excessive concrete substrate flatness deviations continued

Structural cracking (greater than 1/16 in. (1.6 mm) with vertical edge displacement) caused by: • Exceeding concrete slab concentrated load capabilities, settlement or design deficiencies

Tile lippage/jointing solutions • Increase grout joint width to 3/16-1/4 in. (4.8 - 6 mm) for flatness tolerance of 1/4 in. in 10 ft. (6 mm in 3 m) or agree that lippage can exceed recommended tolerances Structural Cracking – edge displacement corrected by: • Repair and grind – crack injection with low viscosity structural epoxy or polyurethane; grind slab flush/flat • Remove/replace sections of concrete per engineer

Request for Information for Floor Flatness Requirements – Letter

SAMPLE LETTER FOR TILE CONTRACTOR

Date

Company Address City, State Zip

Refer to Floor Flatness Chart on page 48

American Society of Concrete Contractors (ASCC) Position Statement #6 found on page 50.

RE: Project

Floor Flatness Requirements

This project includes large format tile (any one side greater than 23 in. [0.58 m]). Floor flatness tolerances specified for this project in section CSI Master Format 03 30 00 Concrete and Master Format section 09 20 00 Tile do not mandate the toler ance needed for a large format tile. Please provide an allowance for the additional costs that will be incurred to meet the floor flatness needed for large format tile or specify the applicable TCNA Handbook for Ceramic, Glass, and Stone Tile Installa tion method to be used.

Please reference attached copy of American Society of Concrete Contractors (ASCC) Position Statement #6 regarding large format tile.

Name and Title Company

This document is compiled by the NTCA Technical Committee and published by National Tile Contractors Association, Inc. • P. O. Box 13629 • Jackson, MS 39236 U.S.A. The disclaimer on page 1 and the introductory comments contained in the complete Reference Manual are applicable to copied or excerpted parts.

NTCA Reference Manual | 2024 / 2025

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Chapter 2 | Substrates