Keyfix Cavity Tray System Exceeds Regulations on Housing Development

  • 30 Sep 2022

Keyfix’s Non-combustible Cavity Tray has provided the effective solution to the government mandate for cavity trays with limited combustibility on a major South East London housing development.  

The Southmere housing development is being built as part of a regeneration project designed to revitalise the Harrow Manor area of Thamesmead. Set in a vibrant lakeside area, Phase 1 of the new Southmere Village will generate 404 high-quality new homes, commercial and public realm spaces.

New residences will be mixed tenure units, including shared ownership and affordable rent units within a range of attractive tower block and town houses.

Valued at £126 million, Southmere Village is designed by Fourpoint Architects. With a programme duration of two years, this is one of the largest projects that Keyfix has worked on to date.

Working alongside contractor Durkan and brickwork contractor Landmark Brickwork, Keyfix supplied 11,946m of its Non-combustible Cavity Trays (NCCT), 7,173 corners, and 21,113 weeps to form Phase 1 of the project.


A challenge arose when the change in building regulations coincided with the Southmere development. Building Regulations Approved Document B on Fire Safety states ‘materials achieving limited combustibility cannot be deemed to meet the requirement using an alternative classification method’.

Now needing to comply with new regulations, Durkan urgently required a third party-rated solution with limited combustibility, made bespoke for the project. 

The unique design of the building took a complex shape, with many returns and steps arranged in the brickwork, as well as inset balconies, brick corbelling, brick features, glass reinforced concrete panels, and a variety of reveals, ranging from 102mm to 450mm in length. The layout also included cavities of varying widths and a highly complex range of masonry support systems which needed to be protected; Keyfix’s NCCT offered the ideal solution to these challenges. 

Paul Turney, Technical Manger at Durkan, comments: “We were very pleased with Keyfix’s product and service provision on the Southmere project. The Keyfix NCCT already offered compliance with Approved Document B standards, making it the obvious choice.

“We also had Keyfix personnel on site for design meetings, Toolbox Talks, as well as receiving a full technical review of architects drawings, a comprehensive mark-up and a scheduled breakdown of component locations, providing full support to our team.”


Furthermore, on this project, Keyfix had a very tight lead time for deliveries, in addition to an extremely congested site. Logistically, the deliveries would be difficult, as not all nine buildings across the three blocks in Phase 1B were being constructed at the same rate, and there was a narrow window to unload deliveries.

Keyfix overcame this by planning ahead and being highly engaged with staff on-site to ensure that the product was being delivered at the right time.

The Keyfix NCCT was specified as it exceeded the criteria to the new building regulations set out in Approved Document B, which states that buildings utilising steel frame systems in the external cavity must have limited combustibility.

The Keyfix NCCT is a non-combustible, A1 fire-rated cavity tray system. It is an effective solution to provide DPC protection over lintels, masonry supports, soffit systems and other elements in the cavity such as fire barriers.

The NCCT was also specified due to the synergy with sister company IG Masonry Support, which supplied various products including essential masonry support systems to this major development.

Keyfix’s foresight and planning on this project allowed Keyfix to work with IG Masonry Support to suitably locate non-combustible cavity trays where required over the masonry support, while ensuring that no clashes occurred within the cavity.

The NCCT also has a lifespan of 125+ years, future proofing the building. Moreover, the Keyfix Non-combustible Cavity Tray system differs from others, as it doesn’t rely on tape or mastics to form its watertight joints, thus removing the prevalent cause of product failure and creating a more robust system altogether.

Kieran Coyle, of Keyfix, adds: “Meeting safety standards is essential in construction. The Keyfix NCCT exceeds the regulations set out in Approved Document B, futureproofing buildings and ensuring the builder and end-user peace of mind.

“On this project we are pleased to have worked closely with Durkan to get all the details through the rigorous approval by NHBC.”

The Thamesmead regeneration project is still in development, with Southmere Phase 1B homes set to become available in summer 2022. The Keyfix Non-combustible Cavity Tray has been fundamental to creating a safe and enduring development that will constitute a vibrant area of south east London. 

For more information about the Keyfix range of non-combustible solutions download the product guide or visit

For technical support, call 028 8676 7508 or email [email protected]

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