Warranty Position Regulatory Position and Guidance Exemptions Does B4 still apply?
Green indicates we consider our position best practice and not in dispute Grey items cover the December 2018 Amendments, Approved Documents and MHCLG's own FAQs and advice notes Green indicates that the item IS exempt from Regulation 7(2), in accordance with Regulation 7(3) Green indicates that B4 still applies, and refers to relevant parts
Yellow indicates our position has the potential to be subjective   Red indicates that the item is NOT exempt. Refer to Regulation 7(3) Red shows that B4 no longer applies


Warranty Position

Definition: Curtain walls including window wall or coupled window screens containing windows and doors. Note: Curtain walls include stick systems and unitised, both of systems incorporating pressure plates, structural bonding, or toggle methods for retaining the glass units

Requirement: Window screen frames are exempt. The MHCLG have confirmed curtain walls are windows. Therefore curtain wall frames are exempt

They are exempt unless there is the potential for B4(1) to be contravened, e.g. if the curtain wall mullions / transoms are manufactured from combustible materials (e.g. upvc, timber etc) and are installed in a manner that facilitates the propagation and spread of fire. In this instance an assessment* would be required.

Note: Infills are not exempt.

Is the position indisputable? Yes.

* Assessment need to be carried out by an experience and competent (in the field of building envelope fire engineering) e.g. a fire engineer.

December 2018 Amendment

Reference: 7(2)(iii).

Reference titles: Window frames and glass.

Approved Document

Reference title(s): 10.15(d).

Reference: Windows frames and glass.

MHCLG FAQS / Advice Notes

Reference: Section 9.

Reference title(s): How does the ban apply to curtain walls? "Conventional curtain walls consisting of mullions, transoms and glazing can be considered as a window frame."


Is the item exempt from Regulation 7(2), in accordance with Regulation 7(3)?: Yes.

Reference: 7(3)(j).

Statement: Window frames and glass.

If exempt, are there any restrictions on the use of the system, component or material given in the guidance in ADB vol 2? Window spandrel panels and infill panels must comply with Regulation 7(2). Combustible thermal break materials should be limited in size to the minimum required to restrict the thermal bridging.

Does B4 still apply?

Yes: Reference: B4-(1)

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Disclaimer: The information in this document is believed to be correct in light of information currently available and at the time of publication but is not guaranteed. Neither LABC Warranty nor its agents can accept responsibility in respect of the contents or any events arising from the use of the information contained within this site. The guidance provided does not replace the reader’s professional judgement and any construction project should comply with the relevant Building Regulations or applicable technical standards. For the most up to date LABC Warranty technical guidance please refer to your Risk Management Surveyor and the latest version of the LABC Warranty Technical Manual.