Background:
The Briggait is home to a vibrant creative community, producing art, architecture, digital design and leading cultural organisations. Converted in 2010 and managed by Wasps, an established arts charity, it is a successful and sustainable operation, with the 1873 hall regularly used for events, markets and exhibitions.
However, The Briggait was only partly rescued from dereliction and decline. Now, the building on Clyde Street, which was originally used as the city’s fish market, has been brought up to date with an extensive redevelopment programme.
As expected with a building of this age the existing fabric of The Briggait, and more specifically the roof areas, were showing signs of age and varying degrees of deterioration and were desperately in need of maintenance and repair.
The roof had suffered from an ongoing issue with water ingress due to loose slates, blocked valley gutters and water visibly ponding within the gutters. Failing sarking and joints within the lead gutters were also not properly sealed, causing weak points that allowed water to get into the roof build-up and the interior of the building.
Premier Specialist Roofing Contractors Ltd, worked with the main contractor, Clark Contractors, on the 1889 and 1904 Hall Roofs as part of an extensive phased refurbishment to bring the Clydeside Halls back into use. The work has brought the remainder of the market hall complex back into use by transforming the rear halls, corner block and gap site into a creative industry hub that reconnects the building with the River Clyde and secures this important historical landmark for the city.
Roofing product choice:
The following products were used in the restoration:
- New Burlington Blue/Grey size 14/10 random slates were chosen for their durability and aesthetic compatibility with the existing roof, maintaining the historical character of the Grade A listed building. The slates’ size and quality were deemed suitable by the conservation architect, ensuring they could withstand the local climate and meet conservation guidelines.
- Regraded Welsh purple slates
- Welsh grey slates
- Proctor Roofshield breathable membranes were selected for their superior moisture control and breathability, essential for preserving the wooden structures beneath.
- 85mm and 60mm Rockwool Flexi insulation (0.038 W/mK) was chosen for its high thermal performance, contributing to the building’s improved carbon efficiency.
Installation challenges:
The conservation-led project required any products used in the work to blend seamlessly with the harmony of the original building. However, at the same time, the building was suffering from issues with cold spots limiting the availability of all the spaces all year round. The work also needed to address ongoing issues with the building fabric. To conserve and enhance the historic environment, planning stipulated that, as a Grade A listed building, matching new or second-hand natural slates should be used on The Briggait roof.
This proved to be a complex tendering process. The products on the roof had to match the existing diminishing course pattern of the existing slate while also replicating any decorative details and working with the roofline. AccuRoof, part of SIG Roofing provided assistance and support throughout the process.
Although the traditional roofing material in the area is Scottish Slate, this was not viable for the 1889 roof because they were too small for the elevation aspect. By utilising their knowledge of the slate in the local area, AccuRoof, had the option to offer several alternatives to the roofing contractor which would maintain the heritage of the building.
Initially, a Spanish slate was considered but had to be discounted because planning stipulated a preference for slate sourced from British quarries. Instead, Burlington slates supplied by SIG Roofing, were selected to cover the entire roof.
Workmanship:
The 1889 Hall is a warehouse-type building made from an 1800s iron frame with 125mm tongue and groove timber sarking. The roof build-up consisted of slates, roof membrane, sarking, air gap, insulation and birch-faced ply soffit boards. The 1904 hall is a large volume Victorian industrial ‘shed’ with cast iron columns and steel trusses. The timber and slated roof has roof glazing including a lantern light running the full length of the hall. The roof is split into main areas of top chord mitigate and purlin mitigation with hips and rooflights.
The slates were first removed to the full roof and graded for their reusability. The timber on the halls, used for louvres and cladding, was weathered and decayed and had to be replaced. Sarking repairs were undertaken in line with a rot report ensuring replacement sarking was of matching thickness and butt jointed set with 3mm penny gaps to permit ventilation. Any structural repairs were undertaken in line with the structural engineer’s report, drawings and specifications. All lead works were replaced with Code 5, Code 6, Code 7 or Code 8 lead to LSA guidelines. Before laying the slates, all existing roof membranes were removed and replaced with Proctor Roofshield, a breathable membrane. New Rockwool Flexi insulation (0.038 W/mK) was introduced below the existing sarking installed within the purlin zone to a thickness of 60mm on the 1889 hall and a thickness of 85mm on the 1904 hall with a 40mm ventilated cavity maintained with an 18mm birch-faced plywood soffit board finish.
The roofs were then finished in a mix of existing and second-hand slates on the 1904 hall and new Burlington on the 1889 hall.
The project benefitted from the expertise of the roofing contractors experienced team on this project. Contractors are only allowed to install the roofing systems supplied by their roofing materials and specification supplier if they are trained in their products. They are also regularly assessed by the roofing materials and specification supplier on the quality of their work by their technical team at AccuRoof. Their expertise ensured that the work was of the highest standard, meeting both conservation requirements and modern performance standards.
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