The Project

At the beginning of 2016, CS Developments (Manchester) Limited embarked on developing a new build residential scheme project in the heart of Manchester. Featuring an assortment of two and three bedroom apartments, the project is based in a highly accessible location within Manchester’s City Centre and is within walking distance of the City’s vibrant economic, civic, culture and leisure hub. Originally a vacant brownfield site, the project aims to be a landmark development in the City.

The Cambridge Street development includes two tall residential towers of 22 and 29 storeys, providing 282 residential flats in total. The apartments will deliver much needed new residential properties, given Manchester’s projected economic and population growth estimates; Manchester’s population is forecast to reach 625,000 by 2025.


The Challenge

Although the project’s location is one of its biggest selling points, it also acts as a challenge for the construction and design team. Due to its close proximity to the city centre, the proposed designs need to respond to the character and appearance of its surrounding areas.

As well as abiding to the local surroundings, the contractor was looking for a solution that achieves a U-value of 0.18 W/m²K in order to comply with building regulations. In addition to the thermal insulation requirements, the building contractor also placed strong emphasis on sourcing a Euroclass A1 product – the highest class for non-combustible products. As part of a high rise building, all products used have to be approved by the Local Authority Building Control (LABC) as an acceptable solution above 18 meters.

With most fires occurring in domestic dwellings, high rise flats have increased risk potential in the event of a fire. The project’s cladding system and insulation materials must conform or exceed the regulation for limited combustibility defined in section B4 of Approved Document B External Fire Spread – The Requirement

Finally, working on a high rise building creates a number of challenges during construction and installation. The materials selected have to withstand external elements, with minimal or no protection, to ensure a smooth and undisruptive installation phase.  


The ROCKWOOL Solution

As a high rise building, the project specification placed a lot of emphasis on specifying a Euroclass A1 product to provide an approved fire solution above 18 metres. Thanks to its retardant fire-stopping and non-combustible stone wool technology, ROCKWOOL is one of the leading fire prevention and protection insulations. ROCKWOOL RAINSCREEN DUO SLAB® complies with Approved Document B achieving the highest Euroclass classification: A1

With its multi-beneficial stone wool technology, RAINSCREEN DUO SLAB® achieves the project’s strict technical performance with a U value, or thermal transmittance, of 0.18 W/m2K and resilient acoustic insulation. As a fibre based product, RAINSCREEN DUO SLAB can be amalgamated to slot into very tight spaces, leaving no empty gaps and achieving optimum thermal performance. Maintaining its shape in the long term by not moving, shrinking or warping.

Based in the city centre of Manchester, the final appearance of the building was crucial in the design and specification stage. The insulation can be easily rendered to accommodate the project’s strict aesthetic requirements using a wide range of available aesthetic tissue faces.

“As a project manager, I have to make many decisions each day, but specifying RAINSCREEN DUO SLAB® for this multi-million pound project was one of the easiest decisions I had to make,” comments Pete Cregeen, Project Manager at Renaker Build.  “As a new build, high rise building, we had a strict technical specification to meet, which RAINSCREEN DUO SLAB® effortlessly achieved. I am most impressed with the company’s streamline route to fire compliance with Approved Document B  and fire safe solutions for high rise buildings over 18m.  In comparison to other insulation solutions, there was no alternative.”

As well as achieving the project’s strict technical provisions, the specified insulation also had to withstand a number of installation requirements. Due to the building scaling over 18 meters, it was essential for the product to withstand inclement weather during installation.

Specifically designed for high rise buildings, ROCKWOOL RAINSCREEN DUO SLAB® features a dual density insulation board that incorporates a robust outer surface and a resilient inner face. By compressing the primary fleece onto the top 50mm of the insulation, the product can be used, unprotected, in conditions of severe climatic exposure, including strong wind and rain as experienced at high altitudes. The Building Research Establishment successfully tested and approved RAINSCREEN DUO SLAB®’s wind resistance performance, confirming its ability to exceed the maximum UK basic wind speed of 56 m/s.

In addition, the RAINSCREEN DUO SLAB® requires fewer fittings during installation compared to other standard stone wool slabs, minimising installation time. CS Developments (Manchester) Limited installed the product using vertical and staggered horizontal butt slabs. Using tight butt joints, the slabs become seamlessly interwoven when installed, eliminating any extraneous heat loss. This also prevents water transmission through the insulation layer. In total, 13,000m2 of 125mm RAINSCREEN DUO SLAB® was specified for the project.     



As well as finding a solution to comply with a multi-challenging and strict specification, the unpredictability of the English weather can disrupt the progress of many building constructions.  ROCKWOOL provided Renaker Build with a product that not only achieved every technical requirement, but is able to withstand external elements unprotected, providing a cost-effective overcladding solution in Manchester’s city centre. 

Project Location

Cambridge Street

1 Cambridge St
M1 5GB

We are delighted with the ease of installation and the speed at which we could erect the building’s rainscreen. ROCKWOOL goes beyond supplying the product and provided fantastic support. Designated technicians were regularly on site during the planning stages and are readily available throughout the installation phase to ensure satisfactory product installation. This additional service provides invaluable support for our men during construction.

Pete Cregeen

Renaker Build
Project Manager
Cambridge Street Project - RAINSCREEN DUO SLAB
Cambridge Street Project - RAINSCREEN DUO SLAB
Cambridge Street Project - RAINSCREEN DUO SLAB