An external wall insulation (EWI) system designed by Sto has ensured two residential tower blocks meet stringent fire safety requirements.

Located in Tower Hamlets, Gayton House and Sleaford House are managed by housing association Poplar HARCA. Following amendments to Building Regulations, which banned the use of combustible materials in external walls of high-rise buildings above 18m, StoTherm Mineral K was specified to replace the existing EWI system.

BBA-certified, StoTherm Mineral K comprises mineral fibre insulation boards and the system is classified with an A2-s1, d0 reaction to fire in accordance with BS EN 13501-1.

Working on behalf of Westminster Building Company, Square 1 Architectural Solutions was responsible for removing the existing EWI and installing the StoTherm Mineral K system onto four elevations on each 23-storey block. The non-combustible mineral fibre insulation boards were secured to the existing concrete substrate using adhesive and mechanical fixings, and without the need for additional expansion joints.

A StoLevell Duo Plus reinforcing coat embedded with Sto-Glass Fibre Mesh was then applied to the face of the insulation boards. This was followed by the application of 1.5mm stippled StoSilco, a silicone resin render that provides high levels of water repellence to protect the walls from weathering.

Andrew Downer, Director at Square 1 Architectural Solutions, said: “Following an analysis of the existing external wall insulation, Sto developed a suitable specification which eliminated fire safety concerns. Thanks to the A1 non-combustible mineral fibre insulation boards, the blocks will benefit from unrivalled fire protection while the single leaf construction ensures excellent thermal performance for the residents, without reducing the interior space.

“Removing the existing EWI system on two 23-storey blocks was challenging but the installation of StoTherm Mineral K was straightforward. This enabled us to deliver the project quickly and effectively, minimising disruption for residents.”