Cupa Pizarras’ Heavy 3 slate

Cupa Pizarras‘ Heavy 3 is a blue black slate with a slightly gritty texture.

It is produced in two thicknesses, 3.5mm and 7-8mm; the thicker variant being the preferred choice for a project in Scotland with the extra thickness and weight giving it strength to withstand the high wind speeds and driving rain.

The dramatic boomerang-shaped roof at this award-winning country house in Stirlingshire has been created using 900m2 of CUPA PIZARRAS’ Heavy 3 roofing slate. The roof plays a dominant role in the design of this contemporary Scottish home, which won the Individual New Build or Small Development category at The Herald Property Awards for Scotland.

Providing a defence against the elements, this warm roof construction also introduces rooflights and dormers, maximising space and light – both design priorities for the homeowners. Featuring a simple continuous ridge along the house, the large roof expanse is punctuated by four tall chimneys.

With a three-coat render system, called StoLotusan, forming the external envelope, builder Ian McDonald at Glasgow-based IMD Developments constructed the house traditionally. He says: “One of the interesting parts of the project was detailing the large roof overhangs, which are timber clad to the underneath. We all worked closely with the engineer to mitigate the risk of wind uplift.”

Helping the building to achieve a good SAP rating, the warm roof installation, pitched at a 35° angle, comprises a steel-framed structure, 450mm-deep timber rafters, 400mm thickness of Rockwool insulation, a 50mm air gap and sarking boards. Compliant with Scottish building regulations, sarking is familiar to Scottish new builds and offers added strength and weather protection. Fixed beneath the Heavy 3 slate is a layer of Proctor Roofshield breather membrane.