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Why use waterproof cement board

Apr 19, 2023

PermaBASE WP Waterproof Cement Board is ideal for interior wet areas, such as shower enclosures, where waterproofing is essential


A Google image search for the term “shower trends” can quickly demonstrate just how far this key bathroom feature has come since the era of the fiberglass shower/tub combo. Today’s walk-in showers — with their frameless glass doors, built-in shelves and benches, and floor-to-ceiling tiled walls — offer homeowners increased functionality with a touch of modern elegance. However, these larger showers, often with ornate ceramic tile patterns, also require more grout and create even more surface area for water to penetrate and damage the wall framing, which can result in mold, mildew and wood rot.

The cost to repair the damage from such a leak within a finished shower enclosure can be significant and time-consuming. The installation of waterproof cement boards manufactured by PermaBASE Building Products, LLC, an affiliate company of National Gypsum Company, can prevent water from causing harmful and expensive damage.

PermaBASE WP® Waterproof Cement Board combines the strength and benefits of PermaBASE® Cement Board with a waterproof core,” said Tony Fuller, product manager, cement board, PermaBASE Building Products. “It’s ideally suited for interior wet areas — including any size shower enclosure — where waterproofing is required or desired.”

How does using waterproof cement board eliminate the need for an additional waterproofing membrane?

In general, cement boards are a highly moisture-resistant building material that can withstand the damp conditions found in bathrooms and showers, where water can accumulate and seep into the walls over time.

When using a standard cement board for a waterproofed shower enclosure, installers must also apply a liquid waterproofing membrane on the entire wall structure. With PermaBASE WP, they need to apply waterproofing/sealant only at joint seams, fastener heads/penetrations and exposed edges.

“Using PermaBASE WP can result in significant cost savings because installers typically use 75% less liquid waterproofing/sealant for a shower enclosure installation,” Fuller noted.

Discover the advantages of PermaBASE WP:

  • Waterproof core eliminates the need for a liquid waterproofing membrane on the entire wall structure
  • Moisture and mold resistant
  • Lightweight and easy to cut
  • EdgeTech® reinforced edges allows for closer fastener application of nails or screws at the edge without crumbling or spinout
  • Smooth board surface makes it an excellent substrate for tile and other decorative finishes

"Using PermaBASE WP can result in significant cost savings because installers typically use 75% less liquid waterproofing/sealant for a shower enclosure installation."

Tony Fuller


Tony Fuller

Product ManagerPermaBASE Building Products

What makes cement board waterproof?

During the manufacturing process, a proprietary waterproofing ingredient is added to the cement core of PermaBASE Cement Board, transforming it into PermaBASE WP. This waterproof core helps prevent harmful and costly damage while the combination of cement and a fiberglass mesh give the board exceptional strength and durability.

ANSI A118.10: Water penetration testing

To document the product’s ability to remain waterproof when exposed to water for a prolonged period, National Gypsum tested PermaBASE WP per requirements of ANSI A118.10 American National Standard Specifications for Load Bearing, Bonded, Waterproof Membranes for Thin-set Ceramic Tile and Dimension Stone Installation.

PB WP Waterproofness

The ANSI A118.10 test seals a 24" water cylinder to the test board, creating direct water pressure on the surface and measuring any moisture content that passes through to the opposite side of the board. Even after seven days of direct exposure, no water penetrated the PermaBASE WP cement board, meeting ANSI A118.10 requirements for waterproofness.

“Not only is PermaBASE WP deemed waterproof by ANSI A118.10, but it has also proven to help inhibit mold growth, receiving the highest possible scores on two industry-standard mold tests: ASTM D3273 and ASTM G21,” Fuller said. “The product has also achieved UL GREENGUARD Gold Certification for low chemical emissions into indoor air during product usage.”

UL GREENGUARD Gold certification is an industry standard for low-emitting products and materials. Products that meet the UL GREENGUARD Gold standard have been tested and verified to have low chemical emissions, making them safe for use in indoor environments such as homes, schools and healthcare facilities.

These third-party tests prove that PermaBASE WP Waterproof Cement Board is an effective solution for creating moisture-resistant shower enclosures that will last for many years.

Visit the PermaBASE WP Waterproof Cement Board page for product details and other technical data.