BATHROOMS & KITCHENS
MARMOX HOLDING THE LINE ON NHBC WETROOM REQUIREMENTS
Updated guidance puts full-system waterproofing under the spotlight and Marmox is ready.
The year 2025 marks 25 years since Harry Parsons founded Marmox UK Ltd— and for many in the bathroom and wetroom sector, it also brings back memories of when Marmox Multiboard first arrived on the market. Back then, the idea of a fully waterproof, insulating tilebacker board was a major leap forward from conventional plasterboard.
Now, a quarter of a century later, the NHBC has updated its guidance to reflect what many have long known: gypsum-based boards are not suitable substrates in wet areas. New guidance introduced in section 9.2 / 06 of the NHBC Standards— effective from January 1st, 2025— specifies enhanced waterproofing requirements for bathrooms and wetrooms. Full tanking is now required in rooms where the walls and floor are likely to be regularly wetted, especially where power showers are installed. In lower-risk environments, waterproof grout and adhesive may suffice, though specifiers are urged to consider potential changes in water use over time.
The NHBC guidance also discourages the use of magnesium oxide boards due to their susceptibility to moisture-related deterioration.
Manufacturers now face the challenge of demonstrating that their systems— not just individual products— provide a continuous waterproof barrier. Marmox is among the first to undergo additional testing through the BBA to verify full compliance. Multiboard, a cement-coated extruded polystyrene board, forms the foundation of a comprehensive wetroom system that includes Marmox Self-Adhesive Waterproof Tape and MSP 360 Sealant & Adhesive.
Mark Bowman, Technical Manager at Marmox, explains:
“ The new standards require proof that water can’ t get through any part of the installation— including the joints. Our BBA testing involved constructing a tank-like structure, treating the seams just as we would on-site, and filling it to test for leaks. The Marmox Multiboard system passed with confidence.”
The updated BBA certificate confirms that Marmox Multiboards satisfy or contribute to the requirements of NHBC Standards Part 9, Chapters 9.2 and 9.3.
Looking ahead, Marmox is refining its shower former range with a new drain design, a change in size options, and a pre-bonded membrane section for easier installation. These updates— alongside new accessories showcased at Installer Live— reflect Marmox’ s ongoing focus on robust, compliant wetroom construction.
For more information visit www. marmax. co. uk
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