Scottish school sets tough test for Redland Cambrian

Lochwinnoch Primary School has provided a showcase for Cambrian Slate, showing how an early 1900s traditional building can still retain its original appearance using a modern slate substitute, along with traditional slate detailing.

The roof of the 111-year-old school was originally slated using Scotch slate that was at the end of its lifespan so rain penetration was causing a major issue.

The challenge was to retain the school’s original appearance, complete with complex details such as hips, valleys, skews, the interface between flat roofs and around skylights, without costing as much as slate.

Renfrewshire Council and Redland developed the answer to the challenge: Cambrian Slate, precision engineered and manufactured using 60% recycled Welsh slate. “Cambrian was the ideal choice for this project, offering the performance and ease of use of a modern tile, while providing a roof that was sympathetic to the naturally-tiled appearance of the original building,” said James Grant, the Project Architect for Renfrewshire Council.

Redland carried out a full Redland SpecMaster roof specification together with James Grant, examining every aspect of the roof in detail. These included raking valley details, sprocketed eaves, changes of pitch on the roof slope, detailing of top edge and side abutments, flat to pitch lead, ventilation at eaves and ridge, and underlay details.

The council’s concern about the finish of the Cambrian Slates meant that an especially high standard of workmanship was required. This was constantly monitored by an on-site Clerk of Works and Keepmoat’s own site management team, with Redland’s Account Manager dropping in regularly to offer guidance.

As the roof was originally slated there were many traditional details where the modern tiles had to be adapted to traditional details and interface with lead skews and flat roofs. These details were originally finished with slates directly onto sarking so DM Roofing had to adapt this for modern interlocking slates by the inclusion of counterbattens and tile battens, whilst keeping the traditional appearance.

The change of pitch at the hip junction was difficult so Redland produced a sprocket detail that overcame the issue. Another area of difficulty, where the flat and pitched roof meet, included a lead secret gutter – something that was completed with immaculate results.

All work was carried out in compliance with BS 5534: 2014 Code of Practice for Slating and Tiling and BS 5250 Code of Practice for the Control of Condensation in Buildings, ensuring that high and low-level ventilation was provided along with two mechanical fixings for each tile.

On top of the Council’s aesthetic concerns was the issue of working on a live school for five weeks of term time and the careful management that had to go with this. One of the main challenges was keeping a live school wind and weathertight in the face of Scottish weather.

Work also had to be scheduled with the school administration to organise the works to various areas while focusing on leaving a high-quality finish. Overall, the spokesperson for the Council was “absolutely delighted” with the finished roof which was completed on time, with the assistance of two apprentices on site.