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Chapter 3 Backer Boards and Underlayments

Backer Board Definitions................................................................................................................................................... 84

Backer Boards..................................................................................................................................................................86

Introduction to Underlayments........................................................................................................................................90

Poured-Gypsum Underlayments....................................................................................................................................... 92

Tile Over Poured-Gypsum Underlayments and Leveling Materials Caution............................................................................ 93

Tile Over Poured-Gypsum Underlayments and Leveling Materials – Note to the Tile Contractor - Sample Letter for Contractor ....93

Flowable Hydraulic Cement Underlayment (FHU)/Self-Leveling Underlayment (SLU) ............................................................. 94

Loss of Poured/FHU/SLU Underlayment Bond to Substrate.................................................................................................. 95

Underlayment Cracking...................................................................................................................................................96

Underlayment Cracks and Their Treatment – Sample Letter for the Tile Contractor ............................................................ 98

Soft or Powdery Underlayment........................................................................................................................................100

NTCA Reference Manual | 2024 / 2025

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Chapter 3 | Backerboards and Underlayments