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Slab On Ground Preparation and Precautions for Sheet and Liquid-Applied Crack-Isolation and Waterproofing Membranes

Tile contractors are often required to install sheet or liquid-applied Waterproofing and/or Crack-Isolation Membranes (WP/CIM) over slab on ground construction (SOG) before the installation of ceramic or natural stone tile.

The manufacturer’s recommendations must be carefully followed in order to achieve a successful installation and to activate eligi bility for the manufacturer’s warranty. The installer is responsible for thoroughly understanding and following each manufacturer’s requirement(s) and instructions for their products. Curing compounds, sealers, curing accelerators and other surface bond-inhibiting contamination, including sweeping compounds, are prevalent on the SOG concrete. These will need to be evaluated and addressed before any W/P or CIM material can be applied. Slabs need to be well cured, dimensionally stable, and free of cracks, waxy or oily films and curing compounds. Concrete slabs must be adequately absorbent to accept water droplets. If water droplets bead on the concrete surface for more than 1 minute, contact your membrane manufacturer’s representative because the slab may need to be profiled or treated per the membrane manufactur er’s recommendations.

Some manufacturers may require Moisture Vapor Emission Rates (MVER) / Relative Humidity Rates (RH) before their underlayment and/or membranes can be applied.

If the concrete slab does not meet these criteria it may be necessary to discuss the matter with the general contractor or owner before proceeding.

NTCA Reference Manual | 2024 / 2025

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Chapter 4 | Membranes