Prefabricated glass fibre false chimneys, Dormers, canopies & external mouldings

What products does this document refer to?

Off-site manufactured prefabricated false chimneys, dormer units, canopies and external mouldings such as feature corbelling products.

What are the Warranty provider's concerns?

Off-site manufactured prefabricated false chimneys, dormer units, canopies and external mouldings are being marketed, some with and some without third party product conformity accreditation. For those products and systems that do hold third party approval certificates, there is often no evidence of durability or weather resistance.

Also, the installation of some of these products and systems on site have either been found to not follow the manufacturers approved design and installation recommendations, or there is little consideration to how the product interacts with the adjoining construction e.g. at flashings, particularly in respect to weather resistance or movement.

This has led in some instances to water penetration through to the structure occurring which required remediation works being necessary post completion.

Warranty stance

Incorrect design and installation of this type of product is considered to compromise the ability of the respective construction element into which they are built, in meeting with the Functional Requirements and Performance Requirements stipulated by the Technical Manual, notably those relating to product testing and certification, durability, weather resistance and structural performance.

What Developers should action after reading this document?

For Warranty purposes, where such products/systems are to be used on our sites, Developers must ensure that they are clearly identified at the start of a project and a full specification, including the third-party certification documentation, be made available to our Warranty surveyor for a site-specific review prior to commencement.

Any proposed off-site manufactured product or system used as part of the structure or waterproof envelope of the building must be appropriately tested and approved for their intended purpose. Developers should ensure that suppliers and manufacturers of all prefabricated glass fibre false chimneys, dormer units, canopies or external mouldings have a valid third-party product approval issued by an organisation which is accepted by us.

The valid third-party product conformity approval shall clearly state:

• The name of the product and its intended scope of use.

• The service life of the product.

• What exposure and environmental conditions the product has been tested to, the extent and type of testing and the performance achieved.  

• That the manufacture of the product/system has been carried out under a recognised quality management process.

The Developers design team must review this information against the requirements of the Technical Manual before submitting to the Warranty provider – notably considering the aspects of expected service life, durability and weather resistance/exposure for the individual specific site they are intending to use them on.

All components used in manufacturing of the product/system should satisfy Appendix C of our Technical Manual. Where a product is used within a coastal location meeting the definition stipulated within Appendix B of our Technical Manual, the product and any associated fixings used must be appropriately durable for the aggressive environmental conditions.

The Developer should also ensure that site teams have appropriate installation methodology in place for the installation of these types of products. This information should be followed on-site by any installation teams, and must align with the manufacturer’s installation procedure details, as identified in the  third-party product approval certification.

Where manufacturers have pre-formed ancillary products identified in their third-party product approval certification to complete interfaces with the roof e.g. preformed aprons and flashing kits, these must be used and not substituted with other materials (e.g. lead) as this ensures that the installation remains within its intended scope of use and any testing completed as part of the certification process.

Site teams should also be able to demonstrate quality assurance procedures covering installation are in place and are able to demonstrate appropriate controls and checks are being undertaken – particularly for those junction details such as flashings that are created on-site between prefabricated chimney units and the primary roof coverings. These details should be made available to our Warranty surveyor upon request.

Transitional arrangements

In December 2023, a transition date was announced for manufacturers of the above, to have had identifiable products independently assessed and approved by an accredited organisation by 1st June 2025.

To allow further time for manufacturers to complete their certification applications with the various product conformity bodies, we have granted a further extension to the existing transitional period, now extended to 1st July 2027.

Accordingly, from this date, these specific uncertified products will only be accepted on live and new sites where the following requirements are met:

• Only the manufacturers that already have a contract engagement in place with a third-party product approval organisation which is accepted by us are eligible to this transition arrangement.*

• Manufacturers and their relevant products must be included on the CGFMA maintained list of members and products operating under this arrangement.**

• Manufacturers must maintain membership of the ‘Construction Glass Fibre Manufacturers Association’ (CGFMA) to at least 1st July 2027, and the CGFMA audit must continue to be in place for the manufacturers identified products being assessed.

Please note:

* Acceptance under this arrangement does not constitute product approval or certification. We do not undertake product acceptance and it remains the responsibility of manufacturers and designers to ensure products are suitable for the intended purpose and meet the requirements of our Technical Manual.

** Inclusion on this list does not in itself demonstrate compliance with certification requirements.

Evidence of the above conditions must be made available upon request by our Warranty surveyors.

During the transition period, products will be considered in the context of their intended use and associated risk.

Products forming part of the external envelope where weathertightness is achieved through junctions or interfaces, or otherwise presenting increased risk (e.g. parapet cappings, chimneys, dormers, cladding), must demonstrate that critical aspects of the design have been fully resolved prior to acceptance.

Demonstration of design resolution should be supported by clear and coordinated design information appropriate to the stage of construction.

This should include, as a minimum:

• Fully developed and coordinated junction details, including interfaces with adjoining construction, and

• Clear provision for weathertightness, including flashings, abutments, and appropriate drainage paths, and

• Clear identification of installation requirements necessary to achieve the intended weathertight performance, and

• Evidence that the proposed design can be consistently and reliably constructed on site.

• Where this level of design resolution cannot be demonstrated, the use of uncertified products should be treated with increased caution and may be deemed to not be appropriate by the Warranty surveyor.

Conditional acceptance and on-going control

Continued acceptance of uncertified products under this arrangement is dependent on compliance with all stated conditions and appropriate design resolution for the proposed application.

Additional conditions of acceptance may be introduced during the extension period where required, particularly in response to observed performance, emerging risks, or industry feedback, including concerns relating to long-term performance such as water ingress and durability.

The Warranty provider reserves the right to amend or withdraw this extension where they consider conditions or commitments are not being satisfactorily maintained or where the risk to Warranty is considered to be above an acceptable level by us as the Warranty provider.