2024-25_NTCA_Reference_Manual_dig_dwnld

Backer Boards

Problem

Cause

Cure

Rust colored stains coming through the grout.

Use only corrosion-resistant fasteners, or those specifically recommended by the manufacturer. A. Using an alkali-resistant fiberglass tape, properly tape all seams of the back erboard. Prior to applying the tape, pack the seams with a dry set or latex-Portland cement mortar, or the specific setting ma terial recommended by the backerboard manufacturer. Using a flat trowel, strike the setting material over the top of the tape leaving a smooth surface. Note: the use of drywall tape or drywall compound is strictly prohibited for taping backer board seams. Movement gaps or flexible joint sealants might be required by manufacturers. B. Follow the fastener spacing and pat terns recommended by the backer board manufacturer.

Non-corrosion resistant fasteners used when installing the backerboard.

On vertical surfaces, the tile is cracked along the seams of the backerboard.

A. Backerboard seams not properly taped.

B. Fastener spacing and patterns not followed per the recommendation of the backer board manufacturer.

Photo courtesy of the National Tile Contractors Association

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NTCA Reference Manual | 2024 / 2025

Chapter 3 | Backerboards and Underlayments