When Building Regulations changed in 2018 to require non-combustible or limited combustibility materials in external walls, membranes were exempt. Despite this, the industry has continued to evolve, with A2- rated membranes now available for projects seeking higher fire performance standards.
AT PROCTOR GROUP, this has meant developing solutions such as Wraptite®, an airtight, vapour permeable membrane designed to support both fire performance and overall building envelope efficiency.
While Regulation 7(3) permits membranes classified as B-s3,d0, many specifiers now aim for A2- s1,d0 across the full wall build-up. However, focusing purely on fire classification can overlook other critical factors. Membranes play a vital role in airtightness, moisture management and durability, so performance must be considered holistically.
Not all membranes deliver the same balance of properties. In some cases, products with higher fire ratings may compromise on vapour permeability or water resistance. The challenge is to achieve the right combination of fire performance and envelope functionality. A key risk on-site is product substitution. Membranes are often swapped for lower-cost alternatives claiming similar classifications. However, matching a classification such as B-s3,d0 does not necessarily mean equivalent performance or safety.
Fire classifications under BS EN 13501-1 are based on multiple tests, including small flame exposure and the Single Burning Item (SBI) test. To achieve A2 classification, additional calorific value limits must also be met. Importantly, these tests are conducted under specific conditions that can significantly influence outcomes. For example, membranes may be tested fixed to a substrate or free-hanging, and with different installation details such as overlaps, tapes and fixings. These variables can affect fire performance, meaning two products with the same classification may behave differently in real-world applications.
This is why Proctor Group promotes a systemled approach. By combining membranes such as Wraptite® with compatible components like Proctor A1 Cement Board, specifiers can have greater confidence that the installed system will perform as intended. Substituting individual elements reduces this certainty. Differences in test methods, substrates or installation details can introduce unintended risks that are not immediately apparent from product data.
With the introduction of Gateway 2 under the Building Safety Act, there is also increased scrutiny on specification changes. What might previously have been considered a minor substitution now carries greater responsibility.
Ultimately, compliance is only part of the picture. Delivering safe, robust and high-performing buildings requires a joined-up approach to specification – one that considers how all elements of the envelope interact. By specifying complete, tested systems, project teams can reduce risk, protect performance and maintain confidence from design through to completion.
