The government has recently announced their review of the effectiveness of amendments to Building Regulations in England which came into effect on 21st December 2018 and banned the use of combustible materials in and on the external walls of buildings with a storey at least 18 metres above ground level that contain one or more dwellings, an institution, or a room for residential purposes (excluding hostels, hotels, or a boarding house). The priority was to improve public safety by removing the flexibility previously given to designers and making the route to compliance with the Building Regulations clearer for high rise buildings.
The amendments which came into effect on 21 December 2018 meant that cavity trays within masonry cladding and framed backing walls of relevant buildings needed to achieve a reaction to fire classification of A2-s1,d0 or A1. However, the recent Government review now includes details of a temporary 18-month exemption on cavity trays in all forms of construction which will take effect on 1 June 2022.
Following the amendments to building Regulation in 2018, NHBC has worked collaboratively with industry stakeholders including developers, product manufacturers and product certification bodies to achieve compliance with NHBC standards by promoting and supporting the development of system designed cavity trays which address performance requirements including A2-s1,d0 or A1 reaction to fire classification, watertightness, accommodation of movement, durability, and buildability and are independently assessed as being fit for purpose.
Following the Government announcement of a temporary 18-month exemption on cavity trays for Building Regulations purposes, NHBC are continuing to uphold our position for Buildmark warranty purposes by only accepting cavity trays on buildings above 18 metres which hold independent product certification by a product certification body acceptable to NHBC. Information on certification bodies acceptable to NHBC is provided in technical guidance note 2.1/20 which is available on the NHBC website www.nhbc.co.uk.
Cavity trays should be used in accordance with their product certifications including the use of preformed units to simplify detailing of complex junctions e.g., corners, steps and staggers.
