22 Interiors


Marmox holding the line on NHBC wetroom requirements


N


ot only does 2025 mark the 25th anniversary of Harry Parsons setting up Marmox UK Ltd, but it will also


remind many longer-serving bathroom and wetroom specialists of when the manufacturer’s remarkable Multiboard product fi rst became available to the home market – providing them with a totally waterproof, insulating tilebacker board that completely eclipsed the performance of conventional plasterboard. T e fact that it took almost a quarter-century


for the NHBC to tighten its regulations on the unsuitability of certain substrates in these settings will also be a matter of frustration for the countless homebuyers who have suff ered the inconvenience and expense of needing to have the walls – and oſt en the fl oor structure – around baths and showers reinstated due to water penetration and consequential damage. In addition to gypsum plasterboard, the guidance also eff ectively discourages specifi ers from utilising magnesium oxide boards, which have shown a tendency to suff er moisture-related failures. For those who have yet to hear about the


country’s leading warranty provider’s introduction of tough new guidelines to prevent such water damage, we should outline the main content of NHBC 9.2/06, which came into force on 1 January this year. T e document applies to all new homes registered with the NHBC, focusing on waterproofi ng details in bathrooms and other wetrooms. It stresses the need for structural


integrity in waterproofi ng solutions, with particular attention paid to areas around baths and shower enclosures. In wetrooms where the entire fl oor and surrounding walls are expected to be regularly wetted – and where power showers are installed – full tanking is required. In less arduous situations, such as with low-fl ow showers, waterproof adhesive and grout may be considered adequate, though specifi ers should be mindful that fi ttings and fl ow rates may be increased by future occupants. From the perspective of manufacturers such


as Marmox – whose waterproof panels, shower formers, tapes and adhesives are now under renewed scrutiny – the onus is on them to prove that all system components perform together so water cannot penetrate beyond the line of defence. Supportive of the NHBC initiative, Marmox has now had further BBA testing, which confi rms the modifi ed concrete cement-coated XPS boards not only off er a stable background for direct tiling, but also fulfi l the enhanced technical objectives of 9.2/06. In relation to the NHBC Standards 2025,


the certifi cate states: “In the opinion of the BBA, Marmox Tilebacker Boards (referring to Multiboards), if installed, used and maintained in accordance with this certifi cate, can satisfy or contribute to satisfying the relevant requirements in relation to NHBC Standards Part 9 Finishes; Chapters 9.2 Wall and Ceiling Finishes and 9.3 Floor Finishes.”


T e technical manager for Marmox, Mark


Bowman, comments: “Essentially, the new guidance means you have to prove your system is waterproof – not just the boards themselves – which, as Multiboard is a modifi ed cement-faced extruded polystyrene, is a given. So, you have to off er a viable solution for the joints between them, which we do with Marmox Self-Adhesive Waterproof Tape and MSP 360 Sealant & Adhesive. T e actual test conducted by the BBA saw a box – somewhat reminiscent of a Belfast sink – being built, and the prescribed volume of water poured into it to ensure it didn’t leak. T at testing was completed on the 27 February this year. “T e BBA is the only test house authorised


to carry out this testing in relation to the new NHBC guidance, and the fact that the joints were treated in the same way as any sheet of Multiboard installed when tanking a wetroom should give real confi dence to specifi ers, installers, and end users.” Marmox is currently in the process of updating


its selection of shower formers – rationalising the range of sizes, attaching a slightly diff erent model of drain outlet, and featuring a section of membrane bonded onto the back to overlap with the rest of the boarding. T e Marmox stand at this year’s Installer Live exhibition also saw the company showcasing new versions of its popular shower niches and other products that help contribute to a consistently constructed wetroom shell.


01634 835290 www.marmox.co.uk Housing Management & Maintenance August/September 2025


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