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Self-Adhered Crack-Isolation and Sound Control Membranes

MOVEMENT – Movement joints are critical when installing tile over a flexible self-adhered sheet membrane, especially at perimeters and in the center field of tile, as tile will move more freely during shrinkage of mortars and concrete slabs. If installing tile and a membrane over a mortar bed or large areas of underlayments at 1/2 in. (13 mm) thickness or greater, place control joints in the mortar bed or underlayment no greater than 12 x 12 foot centers, with joints extending up to the tile surface. Mortar beds installed over membrane must be reinforced with wire mesh to control shrinkage, as the membrane does not restrain shrinkage movement of the mortar bed. See ANSI A108.1 Cure Problem Cause

Tile installed over membrane is loose, lifted, or has suspect hollow acoustic sounds.

Failure to provide adequate movement joints in the tile, especially at perimeter. Tile and mortars are allowed to expand and contract more freely when installed over a flexible membrane. (POSSIBLY DUE TO DEFLECTION, CREEP OR CURL)

Installation of movement (expansion) joints at perimeters and field of tile are mandatory when installing tile over membrane. Refer to TCNA Handbook method EJ171.

OFFSET OF UNDERLYING CONTROL JOINTS – Tile layout typically does not allow alignment with underlying control joints in concrete slabs. When using membrane to offset control joints in a concrete slab, it is important to observe membrane manufacturer requirements for placement of movement (expansion) joints in the tile, the extent of membrane coverage required, and any requirements for cutting full coverage membrane installations to isolate stress on the membrane. See ANSI A108.17-6.0

Problem

Cause

Cure

Tile installed over membrane at or near control joints in the underlying concrete slab is loose, lifted, or has suspect hol low acoustic sounds.

Movement in underlying control joints is transferred to the membrane, and if tile is restrained, tile will lift upwards and cause loss of membrane adhesion.

Provide adequate movement joints in the tile directly adjacent to locations where tile/membrane bridges underlying concrete control joints. Refer to TCNA Handbook method EJ171.

INCREASED CURE TIME OF ADHESIVE MORTARS – Membranes increase cure time for the majority of latex/polymer modified cement mortars by encapsulating moisture between the impervious tile and membrane. The encapsulated moisture could also affect moisture sensitive stone, or cause increased moisture expansion in more absorptive clay body tile.

Problem

Cause

Cure

PROBLEM 1 – Tile installed over membrane that is loose or damp, and removal of tile reveals mortar soft and damp. PROBLEM 2 – Clay bodied tile or natural stone tile is loose, lifted and has hollow acoustic sound.

Increased cure time of latex/polymer modified mortars and resulting residual moisture.

PREVENTION 1 – Allow additional cure time before opening to traffic or use fast setting type mortars that use special cements that bind residual moisture. PREVENTION 2 – Test moisture sensitivity of natural stone or clay bodied tile prior to installation over membrane.

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Chapter 4 | Membranes