INCA Case Study: Blairgrove & Merrystone Towers​, Coatbridge, North Lanarkshire


Blairgrove & Merrystone Towers

Project Type: Refurbishment

Building Type: Residential, High Rise

System Designer: Structherm Ltd

Installer: Equans

System & Finish: Structherm Structural EWI Mineral Fibre System SR125

U-value Achieved: 0.30 wm/M2

In 2021, Structherm worked with Approved Installation Contractor, Equans to thermally and structurally upgrade two 16 storey high rise properties in Coatbridge, on behalf of North Lanarkshire Council. The original construction of the Blairgrove & Merrystone tower blocks was undertaken by Leggatt, in 1965. The concrete frame structures were infilled with masonry cavity walls that incorporated an autoclaved aerated 3” thick concrete block called Siporex on the main facades. On the other elevations there was a brick skin tied back to the main reinforced concrete shear walls. The tower blocks were refurbished in 1993, using a rain screen cladding which needed to be removed as it no longer met the current regulations.

A structural survey revealed the Siporex cavity walls were in a poor condition and would not fully support a standard External Wall Insulation (EWI) system therefore, in these areas the Structherm Structural External Wall Insulation system (SEWI) was specified. The brickwork areas were remedial wall tied back to the concrete wall therefore the brickwork was adequate to provide support for the new Structherm standard EWI system.

Structherms EWI/SEWI Hybrid system was chosen as a high quality, cost effective cladding solution for these buildings. The Structherm SEWI system was designed to span from floor to floor without any connection to the existing infill walls. This ensures that the Siporex masonry walls no longer had to resist the high external wind pressures and could therefore be retained within the structure.
The cladding was fixed to a new steel channel that was bolted back to the slab edge concrete beam at each floor level.
In the brickwork areas, the Structherm EWI system was attached directly to the external brickwork leaf using strong external wall insulation fixings.

Structherms BBA Approved systems are A2 fire rated incorporating a non-combustible mineral fibre insulation to meet the current Scottish Building Regulations. The combined use of these two different External Wall Insulation systems effectively reinforces the masonry walls, where required, and improves the thermal efficiency of the properties, creating a warmer, drier environment for the dwellings. Structherm also designed the flashings, window cills, parapet wall flashings using finite element modelling to ensure that the high wind loads could be safely resisted whilst optimising the design.

Installation at Blairgrove and Merrystone commenced in 2020 with an estimated time on site of 12 months. This soon got delayed due to the Covid 19 outbreak. This presented a number of problems such as site closure and of course social distancing. Contractors were unable to enter properties to undertake the planned work and as such meant that the project could not be completed until 2022.

The existing tower blocks included a hollow blockwork construction which was being retained. This area required hot dipped galvanised steel windposts which fixed to the face of edge-beams in front of the hollow blockwork. This allowed the Structural insulated panels to be installed over this area using the windposts for support.
The existing balcony walkways also required a capping to be designed which would allow the insulation to abut up to as well as protect the system from the top. A powder coated aluminium capping was fabricated to sit on top of the existing balcony walls with end plates at either side to create a robust solution.

With the tower blocks undergoing an extensive range of improvements, there were multiple contractors working at the same time. This presented a few challenges around getting the insulation system to work with other building elements such as the curtain walling. Structherm ensured that all solutions were robust and weather tight.
One of the big challenges Structherm faced was around the top of the crittall windows at roof level. Structherm engineered a cill to sit under the existing crittall windows which created the overhang required to sit over the top of the EWI. The design also had to accommodate the mullions and bracketry of the curtain walling at the corners of the towers without compromising the stability and protection of the system below. The solution provides a clean finish to the top of the system which also supports the SEWI system with brackets which were incorporated into the design.

The extensive refurbishments make Blairgrove & Merrystone tower blocks a stand out feature in the Coatbridge skyline without the need to decant tenants throughout the works. The use of the Structherm SEWI panels relieve the wind loads from the existing weak cavity walls safely by transmitting the loads directly back to the structural floors as well as thermally upgrading the towers blocks to a U-Value of 0.30W/m2K. The insulation system is an A2 fire rated cladding system which meets the requirements of the Scottish Building Regulations and along with the installation of new windows, doors, curtain walling and sprinkler systems means that the tower blocks have been refurbished to a high standard creating a safer and warmer home for multiple tenants.

Structherm have been pivotal and innovators in the success of the external façade to 4no. existing multi-storey tower blocks on behalf of EQUANS Regeneration Ltd in Scotland.

The initial challenges were to identify a solution post; removal of existing cladding and; extensive remedial works to the existing structure. Despite the challenges with interfacing around new; windows, curtain walling, fire screens and existing services / elements along with varying substrates of differing qualities and/or undulations – Structherms products, design competency and technical innovation ensured that a solution was both viable and possible.

Further challenges persisted post amendment to building regulations (during the design period) and the release of the Grenfell investigation report(s) requiring a redesign of fire strategy and the requirement to undertake fire testing to bespoke areas. These challenges were met face on and Structherm ensured an innovative design met the requirements of current building standards, fire engineer requisites and retained warranties along with meeting the Clients performance requirements.

Additional elements which were originally out with Structherms scope included metal profiles and solutions to areas not previously considered – these were again designed and supplied by Structherm to high standards, and without their involvement would have left EQUANS with a difficulty in sourcing alternative solutions.

It would be my opinion that without Structherms involvement and their technical / design team, EQUANS could not have delivered this scheme or met the Clients performance requirements.

I would strongly recommend Structherm for consideration of any award and having dealt with an array of Façade / insulation designers and suppliers, it has been a breath of fresh air to work with Structherm where nothing really is impossible or a problem to their design team. Their proactive nature in dealing with site issues along with regular visits to support our team has also been extremely beneficial. Their process’s and procedures are of high quality, easy to understand and their assistance / aftersales has been excellent.

We have found no issues with their products, quality control, deliveries or staff – they have been one of our highest performing suppliers and rightly deserved.

Graeme Blackwood

Contracts Manager, EQUANS Regeneration Ltd

The existing tower blocks included a hollow blockwork construction which was being retained. This area required hot dipped galvanised steel windposts which fixed to the face of edge-beams in front of the hollow blockwork. This allowed the Structural insulated panels to be installed over this area using the windposts for support.

Julian Taylor

Technical Director, Structherm

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