Verge trims are a common way to deal with a lack of roof overhang. This is particularly useful on mid-terraced and semi-detached properties. However, with the new year rolling in, the EWI industry group has specified some crucial changes to the treatment of verge trims, as part of an external wall insulation system. At EWI Pro, we have responded and developed a new system to adhere to these standards. In our latest blog, we will discuss what came before, and our brand-new solution.

A background to verge trims

As verge trims are a popular solution, they are a bulk installation option. The volume, therefore, brings additional risk as some installers lack the experience and skill necessary. However, issues are not just related to the skill of the installer. Cold bridging requirements were not in place until PAS 2017 and were only mandatory under PAS 2019. Therefore, the reliance on mastic and single joint installations allowed an excess of water ingress behind the EWI system. The changes to regulations have accelerated since 2021 to tackle the issues:

• Verge trims were banned for PAS use in October 2021, as written into PAS in January 2021.
• In May of 2021, the PAS working group requested an opportunity for the industry to develop more robust solutions
• Agreed changes to PAS went through on December 21 to amend line in 2030 -2019: interfaces with roofs at eaves and verges (where metal or plastic capping and trims shall not be used) unless these are detailed within the document External Wall Insulation Specification for Weathering and Thermal Bridge Control [N1] (see 10.7.1);
• The Verge Trim Committee (VTC) presented to the retrofit task group and got approval to develop new solutions but trials are needed.
• The VTC set up an industry working group of over 40 contractors/system designers and fabricators.

New verge trims and the guiding principles

The new principles tackle several different stress points within the use of verge trims:

• Redundancy of seals: At least two lines of weathering protection. Sealants shall not be employed to provide the primary barrier to water penetration. The additional redundancy is achieved with an additional trim (cover trim) or suitable membrane or flashing. All joints and render abutments must have a double seal to comply with PAS requirements.
• At eaves with insufficient roof overhang: Protection afforded to the top of the EWI system must include a secondary waterproof membrane and/or flashing that tucks under the existing sarking felt where present.
• The overhang must be appropriate for exposure zone and profile type: Fore ‘verge trim’-type profiles: min. 40 mm for moderate exposure, minimum 50 mm for severe or very severe exposure based on BRE wind driven rain map: Ref – BR 262 Thermal insulation: avoiding risks (Appendix A: WP2 (publishing.service.gov.uk). For ‘integrated gutter type’ profiles, minimum 10 mm and as recommended by the profile supplier.
• Gable-to-eaves junctions must be achieved with overlapping, pre-fabricated units/connectors: Site fabrication is not permissible although minor site trimming / bending is permissible if in accordance with the manufacturer’s recommendations. Joints between primary and secondary seals are offset/staggered by at least 100 mm.
• To reduce thermal bridging effects, thermal insulation at gable-to-eaves junctions must be maintained up to the level of the top of the loft insulation or greater, in accordance with the Retrofit Designer’s requirements.
• Gable apexes must be formed using pre-fabricated elements: Site fabrication is not permissible although minor site trimming / bending of pre-fabricated apex profiles is permissible if in accordance with the manufacturer’s recommendations. Where site bent flashings/trims are employed a lead/lead replacement flashing that covers the full depth of the apex profile (see for example Scenario 4- B2) is necessary. Site-mitred apex joints using two separate profiles are not permissible.

EWI Pro operational approach in 2023

The new operational approach surrounding the verge trim regulations is designed to protect the installer and EWI Pro. The new principles will affect our warranty scheme; if the installer fails to present a valid spec and photo of the verge trim installation, the warranty will be rejected. As long as the verge trims follow the agreed new industry principles, then 3rd Party Warranty providers such as SWIGA would be happy to offer a 25 year guarantee. This stands on the basis that the EWI project has been carried out in accordance with the manufacturer’s (EWI Pro’s) specification. However, funded jobs or jobs under PAS 2035 cannot have verge trims. Therefore, the project will require an extension of the roof line.

EWI Pro is in the process of developing our own designs that will satisfy the new principles. We have provided several illustrations for possible solutions to scenarios that contractors may encounter. However, real life scenarios may vary depending on the project. Therefore, we recommend that the contractor contacts our Technical Department for further help.

Inevitably, there will be challenges during the installation process, as there is with any new regulations. The major part of the solution is the installation of a secondary waterproof membrane to repel any water ingress.

Finally, if you have any other questions, give our technical team a call!