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.
