As pitched roof construction continues to evolve in response to tighter building regulations, improved energy performance targets and the rapid growth of solar integration, the role of roofing underlays has become more critical than ever. For housebuilders and specifiers, selecting the right underlay is no longer just about weather protection during construction, but about long-term moisture control, airtightness and regulatory compliance.
Developed by Don & Low, the MultiTX® range of roofing membranes has been designed to meet these modern demands. The range comprises high-vapour-resistance air and liquid barrier underlays that provide a robust, cost-effective alternative to traditional bituminous-based (Type 1F) roofing felts, while offering improved handling, durability and performance consistency.
Designed for Moisture Control and Compliance
Condensation risk remains one of the most persistent challenges in pitched roof design. The MultiTX® range has been engineered with moisture transfer firmly in mind, helping to mitigate the risk of interstitial condensation within the roof structure while maintaining adequate protection against external weather ingress.
MultiTX® membranes function as high-vapour-resistance barriers, limiting moisture movement into the roof build-up and supporting compliance with key UK standards and guidance, including BS 5250. Their performance characteristics make them suitable for use in a wide range of pitched roof constructions, both warm and cold.
Crucially for housebuilders, MultiTX® products within the range hold independent third-party certification. The range includes products certified by the British Board of Agrément (BBA), with additional NSAI approval in Ireland for selected variants, providing reassurance on fitness for purpose, durability and regulatory acceptance.
A Versatile Range for Different Build Requirements
The MultiTX® range consists of four distinct products, each tailored to different roofing demands while maintaining consistent core performance principles:
- MultiTX® Plus (116 gsm) – A lightweight, high vapour resistance underlay suitable for standard pitched roof applications where ease of handling and installation speed are key priorities.
- MultiTX® Pro (145 gsm) – A durable air and liquid barrier offering enhanced strength, excellent low-temperature flexibility and reliable temporary weather protection during construction.
- MultiTX® Maxi (190 gsm) – A heavy-duty barrier roof underlay that provides increased robustness and resistance in demanding site conditions.
- MultiTX® Solar (145 gsm) – Specifically engineered for roofs incorporating integrated solar installations, where additional fixings and penetrations place higher demands on the underlay.
This structured range allows housebuilders to select the most appropriate specification for each project, without changing system philosophy or installation approach.
MultiTX® Maxi: Heavy-Duty Performance, Independently Proven
MultiTX® Maxi represents a key milestone within the range. At 190 gsm, it delivers enhanced durability and long-term protection, making it particularly suitable for exposed locations or projects that require additional robustness during construction.
Importantly, MultiTX® Maxi is currently the only heavy-duty barrier roof underlay on the market to hold a BBA Agrément Certificate. This certification confirms its performance against rigorous national and European standards, validating its formulation, strength and suitability for use within pitched roof systems. For housebuilders, this translates into reduced specification risk and increased confidence at both design and inspection stages.
Installation Efficiency and Site Practicality
Across the entire range, MultiTX® membranes are designed with site practicality in mind. The lightweight fabric construction minimises manual handling issues. At the same time, excellent low-temperature flexibility ensures the membrane remains workable in challenging weather conditions.
MultiTX® membranes are resistant to water penetration and UV-stabilised, providing effective temporary weather protection during construction. Selected products are also available with double-integral tape options, enhancing airtightness, wind uplift resistance, and installation efficiency.
Supporting the Shift to Solar-Ready Roofs
As integrated solar roofs become increasingly common in new-build housing, underlays must accommodate additional system requirements. MultiTX® Solar has been specifically developed to support solar integration, offering a high-vapour-resistance air and liquid barrier beneath photovoltaic systems.
By contributing to moisture control and airtightness while maintaining simple installation, MultiTX® Solar supports compliance with current regulations and guidance on ventilation, condensation risk, and roof durability. Its performance allows designers to simplify roof build-ups in specific applications, helping to reduce material use and labour time without compromising protection.
A Future-Focused Roofing Solution
Manufactured under a certified ISO 9001 quality management system, the MultiTX® range reflects Don & Low’s vertically integrated production approach, ensuring consistent quality and performance control from polymer processing through to finished membrane.
For housebuilders seeking a modern, certified and adaptable roofing underlay solution, the MultiTX® range offers a proven response to today’s construction challenges, from moisture management and regulatory compliance to durability, ease of installation and solar readiness.
