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MultiTX® Maxi: The Only Heavy-Duty Barrier Roof Underlay with BBA Certification Delivers Proven Performance

Don & Low, the UK's renowned vertically integrated manufacturer, is proud to announce that MultiTX® Maxi, the new, heavy-duty barrier roof underlay, has been successfully assessed by the BBA. MultiTX® Maxi is now the only heavy-duty barrier roof underlay on the market holding a BBA Agrément Certificate.

Part of the extended MultiΤΧ® range, MultiTX® Maxi is a high vapour resistance, air and liquid barrier underlay for use in pitched roofs. Weighing 190gsm, MultiTX® Maxi provides enhanced durability and superior protection against the elements, helping to prolong the longevity of the roof. MultiTX® Maxi serves as a modern alternative to traditional bituminous-based (type 1F) roo­fing felts with excellent low temperature flexibility, while also being resistant to water penetration and stabilised against UV degradation.

The BBA Agrément Certificate is a mark of excellence based on rigorous national and European standards that validate a construction product’s specialist formulation, capability and uniqueness. MultiTX® Maxi has undergone a thorough evaluation that has quantified its performance. The BBA has determined that the new MultiTX® Maxi is well suited to its intended use and can satisfy all relevant requirements of the essential building regulations.


Will Campbell, Head of Sales at Don & Low, commented: “The BBA Certificate of MultiTX® Maxi represents a long history of technical competence and countless successes in our Research and Development and testing departments. As a vertically integrated manufacturer, Don & Low maintains total control over every step of the in-house production process. This allows us to maintain the highest quality standards and consistent product performance, resulting in innovative and cost-effective solutions tailored to the needs of the construction industry.”


The extended MultiTX range of barrier roof underlays now consists of four products: MultiTX® Plus (116gsm), MultiTX® Pro (145gsm), MultiTX® Maxi (190gsm) and the specifically engineered for integrated solar roofs MultiTX® Solar.


The BBA Agrément Certificate for MultiTX® Plus, MultiTX® Pro and MultiTX® Maxi can be found here.


For more information, visit 


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Specify & Build

JUNE 2024


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