Background:
The Thomas Rotherham College Woodhurst Building was designed in a style reflective of the Georgian Revival. To preserve its character and ensure functionality for future generations, the building required extensive roofing work. NRA were appointed as the principal contractor to remove and replace the existing roof covering, an area of 500m2. The project required a skilled approach to ensure that the new roof provided both long-lasting durability and aesthetic harmony with the original design. The primary task involved removing the existing slate and installing new materials, carefully selected to maintain the aesthetic integrity of the Grade 11 listed site while adhering to its original slate design.
Roofing product choice:
The new roofing system was completed in Welsh slate from the Cwt Y Bugail quarry, supplied by SIG Roofing, which was chosen for its exceptional quality and aesthetic appeal. This was laid onto a foundation which included a TLX Batsafe breathable membrane and SR Timber Premium Gold graded timber roofing battens, and counter battens for enhanced durability and ventilation.
To upgrade the thermal performance of the property, 100mm loft roll was added to the joisted areas, increasing the insulation levels to 300mm. In the raked areas, 100mm PIR board with foil facing was installed. To ensure proper airflow, counter battens were fitted, and the TLX Batsafe beather membrane applied, contributing to an improved U-value.
Additional materials, including premium-grade lead sheeting, building paper, copper components and sturdy fixings to ensure a secure and long-lasting structure. All materials were meticulously sourced from SIG Roofing to meet the highest standards of performance and reliability.
Reroofing a Victorian slate roof requires meticulous attention to detail. Cwt Y Bugail slate is dark blue-grey with occasional white veins and has a unique riven texture. It is located east of Blaenau Ffestiniog in North Wales, where they have been producing slates since 1840, and the slate was formed by Ordovician slate beds laid down over 470 million years ago. It has a distinctive branding known as relic bedding and gives an extremely uniform, unfading appearance on the roof. It comes in three thickness grades: Capital 5.5mm, County 7mm and Celtic 9mm, the latter of which was used on this project. A total of 30,500 slates. The durability and performance of Cwt Y Bugail slate, combined with the roofing expertise and craftsmanship provided by NRA Roofing experts, ensure that the new roof will last at least 75 years, potentially exceeding a century, much like its original Victorian predecessor.
SIG Roofing also supplied 4750 linear meters of SR Timber PREMIUM GOLD® Roofing Battens for this project. This product meets the specifications outlined in BS 8417:2011+A1:2014 (preservation of timber) and is graded according to BS 5534:2014+A2:2018. Additionally, it is one of the few battens that has passed assessment by the Code for Construction Product Information (CCPI).
More details on the SIGA slate products at https://www.sigaslate.co.uk/ and SR Timber batten at https://sr-timber.co.uk/
Installation challenges:
The project started in July 2024 and concluded in October 2024. A key challenge was in preserving its original character whilst meeting modern design standards and regulatory requirements. Many of the building’s original features had deteriorated significantly over time, necessitating careful restoration or replacement. There were logistical challenges too, being part of a fully operational school campus with an active leisure centre meant managing live operations alongside limited space and strict loading restrictions. Coordinating the sequencing of multiple trades to maintain smooth project progress was a constant consideration too.
Images:
1. SR Timber PREMIUM GOLD® Roofing Batten was used throughout the project
