OBEX Window & Façade Interface Sealing Membranes Whitepaper

Bringing Clarity to the Specification and Installation of Window & Façade Interface Sealing Membranes May 2023 | OBEX Protection Ltd.

WHITE PAPER

Bringing Clarity to the Specification and Installation of Window & Façade Interface Sealing Membranes

May 2023 OBEX Protection Ltd. Version: 01.02.04 Our Ref: 06.U.06.10.01

Contents

Executive Summary

Hierarchy of Regulations

Overview

Installation Overview

Regulatory Requirements

Applicable Testing Standards

Testing Methods

Installation Methods and Techniques

Future Proofing

Product Availability

Conclusion

Contacts

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Executive Summary

This paper provides an overview of the key factors that should be considered when selecting and installing membranes for sealing around windows and façade interfaces. The intention is to assist architects, designers, and contractors in making informed decisions about the use of these materials, ensuring that all products meet the necessary standards of performance and compliance. There are now several membranes being offered to the façade industry for sealing around windows and façade interfaces, both for new-build and re-clad projects. However, due to the varying product specifications, identifying the appropriate membrane for each application can still be a challenge. In view of establishing some consistency on what is a very important part of the external wall build-up, the Government has implemented regulation, such as the Building Safety Act 2022 and issued documents such as Approved Document B, to ensure that window and façade membranes are compliant with the Building Regulations and conform to the relevant test standards. These regulations and standards have helped to clarify the specification process, providing architects, designers, and contractors with clear guidelines regarding membrane performance standards and correct installation practices. Even so, there remains an element of confusion within the industry about which membranes are not only compliant, but more importantly, which ones have also been tested to, and comply with, the correct harmonised standards for performance. This is a critical part of the specification and design process to ensure that the chosen membrane, above all else, performs its primary function and is fit for purpose.

Hierarchy of Regulations

• Regulation 7 • Approved Document B • EN 13984 • EN 13859-2

These standards govern the performance and fire requirements of membranes used in facades.

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Overview

There are two main types of membrane used externally in building façades, each having a different primary function.

• Firstly, there are membranes used to create water and airtight seals around windows and along sheathing board to concrete interfaces. These membranes are commonly referred to as EPDM, a reference to the rubber material from which such membranes have traditionally been made. • Secondly, there are membranes used to provide a vapour-permeable, protective layer when wrapped around buildings behind the cladding. These membranes are usually known as Breather Membranes due to their microporous nature which allows the passage of water vapour to the outside of the building.

These two different types of membrane have been designed for the specific purposes mentioned above, and as such, are different in their material composition, with different performance capabilities.

Although there are differences in the membrane performance requirements of the two applications, fire classification is a crucial consideration for all construction membranes. The Building Regulations and Approved Document B require all components of a façade build-up to have a fire classification. When considering membranes for sealing interfaces around windows, doors, and sheathing board edges, it’s helpful to bear in mind what has traditionally been used – ie. EPDM. EPDM has been used because the material is watertight and airtight, both essential properties for it to effectively perform its primary function. With the introduction of Approved Document B, EPDM is no longer compliant on relevant buildings, due to the combustibility of rubber and its high contribution to the spread of fire.

Consequently, new fire-classified materials have now been developed, which, importantly, still have the water and air-tightness properties required for an effective seal around windows and interfaces.

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Installation Overview

Interface Sealing Membrane & Paste Adhesive

Breather Membrane

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Regulatory Requirements

The construction industry in the UK is subject to a set of regulations and approved documents which govern the construction of new buildings and the safety of the occupants. These include Regulation 7 (Building Regulations 2010) and Approved Document B, which determine the minimum fire classifications for façade materials used on relevant buildings of 18 metres or more in height. Regulation 7 deals specifically with materials and workmanship in the construction of new buildings and is legally binding. It requires that building work be carried out using appropriate materials that meet the statutory requirements and are installed correctly to ensure compliance.

Specifically, Regulation 7 states that,

“….building work shall be carried out so that materials which become part of an external wall, or specified attachment, of a relevant building, are of European Classification A2-s1, d0 or Class A1, classified in accordance with BS EN 13501-1:2007” Some products are excluded from this requirement, including membranes, gaskets, seals etc; but this means exclusion from the requirement for class A2-s1, d0 or A1 - it does NOT mean exclusion from a fire classification altogether. This is confirmed in Approved Document B, which says:

“10.21 (a) Membranes used as part of the external wall construction above ground level should achieve a minimum of class B-s3, d0.”

This is applicable to “relevant buildings” which are defined as those over 18 metres high and have one or more dwellings or rooms for residential purposes/sleeping accommodation, eg. sheltered housing, student accommodation, care homes, hospitals, hotels, institutions etc. Approved Document B is a government document that provides clarity on the requirements of Regulation 7, set by the Secretary of State. It is important to understand that any deviation from Regulation 7 or Approved Document B, requires a written dispensation from Local Authority Building Control. No other body, organisation or industry professional can sign off on this decision.

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Applicable Testing Standards

The Harmonised Standard for interface sealing membranes in construction is EN13984. This standard establishes the membrane’s performance requirements, such as water tightness, reaction to fire, water vapour resistance, elongation at break, and tensile strength. The use of membranes that are compliant with EN13984 and whose primary function is to provide a water and airtight seal, has become a requirement in the construction industry for sealing around windows, doors, and façade interfaces. EN 13984 refers to the EN1928 test for resistance to water penetration, which requires the membranes to be subjected to a water pressure of 2 kPa for 24 hours. Passing this test ensures that the membranes are highly effective at preventing water ingress under high water pressure for a prolonged period. This is particularly important for weather conditions such as persistent rain in colder months, and driving rain during storms, which can quickly lead to a build-up of water pressure. Water will then exploit the weakest point every time it rains. Breather membranes, on the other hand, have a different primary function - that is, to provide a vapour- permeable protective wrap around a building to allow vapour to escape and protect against interstitial and surface condensation. The harmonised standard for breather membranes is EN13859 which requires 2 kPa pressure, but only for a duration of 2 hours. These membranes are breathable due to the material being microporous, therefore not fully watertight. This makes them unsuitable for forming a watertight interface seal around windows and board edges. As mentioned previously, although traditional EPDM is not fire classified, it does comply with EN13984, so it is essential that as we move to fire-classified alternatives for sealing around windows and facades, we don’t neglect the need for the higher water resistance standard that EN13984 requires. In other words, if we prioritise fire classification without considering the performance requirements, we fail to recognise the fundamental reason for using the membrane in the first place. So by selecting window sealing membranes that are not only fire classified but also meet the EN13984 performance standard, architects, contractors and installers can have the confidence that the membranes will be fit for purpose, high-performing and compliant.

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Testing Methods

Window & Interface Sealing Membrane Harmonised Standard EN13984 – applicable water-tightness standard is EN1928, 2kPa for 24hrs

Breather Membrane Harmonised Standard EN13859-2 – applicable water-tightness standard is EN1928, 2kPa for 2hrs

W1 - EN1928 2kPa / 2hrs

W2 – EN13111 <100ml leakage

W3 - EN13111 >100ml leakage

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Installation Methods and Techniques

Any membrane that is installed around windows, doors and interfaces is only as effective as the quality of the installation, so any offers of on-site training from manufacturers need to be welcomed and best- practice techniques implemented.

For a good membrane installation, it is very important to adopt appropriate installation methods and techniques, including the following;

• Compatibility - Firstly, all products should be compatible, and individually tested for their fire classification. • Primer - Porous surfaces such as concrete should be treated with a fire-classified Primer before the paste adhesive is applied. • Paste Adhesive - A fire-classified paste adhesive should be applied to the substrate so that when spread to an even layer it covers the full area to be bonded. A full spread of paste adhesive is also critical in the event that membranes are penetrated with fixings for items such as cladding support brackets, cavity fire barrier brackets etc. If the adhesive isn’t fully spread underneath the membrane, then it will allow water to penetrate underneath, leading to water ingress and a gradual de-bonding of the installed membrane. • Membrane - The membrane is applied to the adhesive and pressed on using a membrane roller to ensure an even bond. • Bond Widths - Membranes that are bonded onto non-porous surfaces such as the side of an aluminium window frame, should have a bond width of at least 20 - 30mm. Membranes that are bonded onto porous surfaces such as concrete should have a bond width of at least 100mm. • Corner Sealing - Particular attention needs to be paid to the sealing of window corners as this can be the most vulnerable point for water ingress. The use of pre-moulded corners gives the best seal, rather than relying on manually cutting and folding the membrane around the corner detail. • Capped Edges - Once the membranes and corners have been installed, all edges need to be capped with a bead of paste adhesive and spread to form a perfect seal. This also prevents open edges from getting snagged or ripped which could compromise the seal.

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Typical Installation Video Guide

Watch the full video here

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Future Proofing

To future-proof against the need for recladding as regulations become more stringent, a compliant membrane that exceeds current standards in terms of fire classification and performance should be considered. This will ensure that the membrane will continue to meet or exceed regulatory requirements for years to come, reducing the risk of non-compliance and the need for costly retrofits. Class A membranes for sealing around windows, as well as Class A Paste Adhesives, are now available on the market.

Product Availability

One of the main challenges that contractors face is product availability, so manufacturers and suppliers of innovative products and systems must contribute to a robust supply chain. This involves the supplier forming strong, mutually respectful relationships with their raw material suppliers to maintain quality levels and continuity of supply.

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Conclusion

Whilst the vast majority of companies indeed want to do the right thing when specifying and installing membranes and other façade materials, some may still attempt to justify the use of the cheapest type of membrane, on the basis that validation has been received from a third-party body. However, it is crucial to note that such endorsement does not absolve them of the responsibility to adhere to the Building Regulations and Approved Document B. According to the new Building Safety Act 2022, anyone involved in any violation of the regulations will be held liable as a result of their actions, whether manufacturer, specifier, or installer. In summary, we need to recognise that façade membranes have to perform a very specific function, even though the regulations governing their use may at times seem slightly ambiguous. Hopefully, this paper has helped to highlight the importance of focusing on two essential requirements;

• Performance – what is the membrane’s primary function, and does it conform to the relevant standard that confirms it is suitable for the specific façade detail requirement?

• Compliance – what testing has the membrane been subject to, eg. Reaction to Fire, Water Penetration Resistance, and does that meet the regulatory requirements of the façade detail?

Many contractors go above and beyond the regulatory requirements in order to future-proof their buildings. This reveals that they understand not only the letter but also the true intent of the Building Safety Act 2022.

But not only that.

It also demonstrates a recognition of the responsibility that we all have - to create safer buildings.

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Contacts

Callum Douss Technical Support Manager

E : callum@obexuk.com

Dan Norman CPD & Specification Advisor

E : dan@obexuk.com

Steve Carvell Technical Copywriter

E : steve@obexuk.com

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