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Roofline Closure Systems

Roofline closure systems are now approved for PAS projects, allowing the use of metal flashings to protect EWI systems instead of extending rooflines.

Roofline requirements vary significantly within a scheme or property, requiring multiple solutions. Since standard details cannot cover all scenarios, a set of Design Principles has been established. These principles provide flexibility while ensuring robust and durable details for long-term protection of EWI systems.

Below are the steps to help you understand the new guidance and the installation requirements going forward.

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1. Design Principles

Roofline closure system solutions are designed according to a set of core Design Principles. This approach ensures that designs can be adapted to accommodate the diverse rooflines and features of different properties, as long as all principles are adhered to. For more information, see below.

Explore The Design Principles
1. Redundancy of Seals– Utilise at least two layers of weather protection.

– Avoid relying solely on sealants for waterproofing.

– Consider additional redundancy with trim or membrane.

– Double-seal all joints.

– Provide secondary waterproofing at eaves.

– Ensure appropriate system overhang per exposure zone
2. Gable-to-Eaves Junctions– Use overlapping, prefabricated units.

– Prohibit site fabrication except for minor trimming.

– Stagger joints by 100 mm.
3. Gable Apexes Formation– Use prefabricated elements.

– Use site bent flashing with secondary lead flashing if necessary.

– Prohibit site-formed mitre joints.
4. Jointing Pieces/Connectors– Use connectors with extended sides.

– Seal connectors to metal profiles.

– Stagger joints by 100 mm.
5. Soffit/Roof Overhangs– Embed flashings/trims into masonry or below cement pointing.

– Overlap joints between redundancy layers by 100 mm.

– Replace sand and cement fillet with flexible mortar.
6. Thermal Bridging– Ensure insulation continuity for minimum thermal resistance
7. Lead Flashings– Limit single-piece lead length to 1200 mm.

– Follow best practice for overlaps and installation of lead or lead replacement flashings.
Explore the Assessment Criteria


1. Relevant DetailsWhat will work with the existing roof line/ substrate.
2. Existing OverhangEnsuring it is consistent across the eaves/ verge.
3. Rafter Positioning
Rafters may need to be boxed in, worked around or altered.
4. Substrate Condition
Where grinding in is to be considered, ensure the substrate is stable and will not be damaged by grinding in.
5. Existing Insulation & Potential Cold Bridging
From installing each detail, ensuring continuity of roof insulation and a minimum thermal resistance of 0.6m²K/W.
6. Corner Details
Confirming how the eaves and verge will meet and what the best detail is (where required, which corner profile is suitable).
7. Existing Features
Such as corbels and quoins will need to be considered and may prevent these details from being installed, resulting in site specific designs being undertaken in line with the Roofline Closure principles.
8. Ventilation
Roof ventilation must not be obstructed/ restricted when installing Roofline Closure Systems.
* Some properties create roof junctions that are extremely difficult to find a solution for, and
therefore extending the properties roofline may be the best option.

3. Second Line of Protection

Explore the Options

The Roofline Closure System Principles require 2 layers of protection across the top of the EWI system.  This can be achieved in several ways; Wetherby offers 2 standard solutions.  Selecting the preferred solution for installation will dictate the specific Wetherby details required.

Membrane Vs Secondary Flashing

  • Installing a membrane below the primary flashing can be a cost-effective solution.
  • Wetherby supply a specialised membrane stop bead (MSB) to be used at the top of the insulation board, providing an adhesive tape to fix the front of the membrane to.
  • Wetherby membranes are supplied in 300mm width roles to simplify installation.
  • Installing a secondary flashing below the existing flashing can be a quick and simple solution.
  • This solution can be less problematic, especially when installing the detail to the top of a property in the UK wind/weather.
  • The Wetherby TCP Under Trim is an angled flashing which can simply be installed below the primary flashing to provide the required protection.
  • The trims interlock/ overlap, and therefore do not require jointing pieces.

4. Guide Information

Wetherby Roofline Closure System Guide

The Wetherby Roofline Closure System Guide provides detailed information on 9 different solutions, the right solution will be dictated by the existing overhang, choice of second line of protection, potential cold bridging and the specific properties existing roof line. 

Page 10 of the guide provides an index to direct Designers and Installers to the right detail.

The guide provides 4 pages of specific install information for each detail which includes:

Including a detailed index, listing all components, product sizes / lengths / dimensions and Wetherby product codes to assist in ordering materials:

5. Application Demo Videos

Here you’ll find a series of demonstration videos that reveal the intricacies of Roofline Closure Systems.

Eaves Detail A1

Eaves Detail A2

Verge Detail A3

Verge Detail A4

7. Minimum Material Specification

The Roofline Closure System principles include a minimum specification for the flashings to which Wetherby components are manufactured:

Minimum Material Specification
1. Suitable Base Material– Minimum Aluminium specifications 1050A.  Minimum Stainless-Steel specifications 304.
2. Minimum Thickness– 1.2 mm aluminium with a tolerance of +/- 10% to be used for trim widths up to 160 mm.

For trim widths over 160 mm or trims to be used in exposed areas, (minimum 50 mm overhang) 1.5 mm aluminium must be considered for added strength and stability.
3. Coating Requirement– Polyester Powder coated aluminium must have a minimum coating thickness of 40 microns to BS or Qualicoat standards and Powder Coaters must be BS or Qualicoat-approved applicators. Pre-coated aluminium must be polyester coated on both sides and the thickness must conform to EN 13523-1.

8. Ancillary Items

There are a number of ancillary items required when installing Roofline Closure systems which are described and listed below with more information in the Wetherby Guide. 

Ancillary Items


Jointing Piecesmust extend 40mm on each side of a joint
Gable ApexesPrefabricated profiles must be used
End CapsRequired on all primary flashings
Gable to Eaves JunctionPrefabricated corner profiles required
Downpipe BoxesRequired at swan neck junctions
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Contact the Team at Wetherby Building Systems

We understand that embarking on a construction project is a significant endeavor, and we’re here to support you every step of the way.

If you have any inquiries, require additional information, or would like to discuss your specific project needs, please don’t hesitate to reach out. Our dedicated team of experts is ready to listen, collaborate, and provide tailored solutions.


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