Piode (Stone Roof Slabs)

Piode (singular pioda) is the Italian and Ticinese term for flat stone slabs used to roof buildings in the southern Alps. Stone-slab roofs of this kind cover rural houses and farm buildings in many valleys in the Swiss canton of Ticino, such as the Maggia valley, and of neighbouring parts of Italy. They are heavy, very durable and strongly tied to local geology and landscape.

Material

In Ticino the characteristic roofing stone is gneiss, split by hand (a spacco) into slabs of traditional shapes and sizes. Craftsmen who can hand-cut gneiss into thin slabs have become rare. Limestone slabs are traditional only in the Mendrisiotto in the far south of the canton.

Construction

German-language building references describe Ticino stone slabs laid almost horizontally on a cross-batten structure, giving a roof that is very stable and durable but costly to build. Switzerland traditionally used much natural stone on roofs, especially in Valais and Graubünden as well as Ticino.

Protection and subsidies

Ticino supports traditional roofs on rural buildings (rustici) through cantonal subsidies. These were introduced in the 1970s, abolished in 2003 to save money and reintroduced in 2012 alongside the cantonal plan for rural buildings (the PUC-PEIP "Piano dei rustici"). In December 2016 the cantonal parliament approved a credit of CHF 3.6 million, of which CHF 2.5 million was for traditional roofs. Under the directive of April 2017:

• Piode roofs receive CHF 200 per m² of roof actually built, measured along the slope.
• Only local gneiss split by hand qualifies; machine-worked slabs, non-local shapes and other stones such as quartzite are excluded.
• Coppi (traditional curved clay tiles) receive 25% of the extra cost over a standard tile roof, for conservative restorations only.
• Eligible buildings include those in listed localities, groups where at least two-thirds of roofs are already traditional, and buildings in protected landscapes whose original roof was piode.

The directive also notes that corrugated metal and grey concrete tiles are not part of traditional rural architecture.

Related traditions

Stone-slab roofs are part of a wider European family that includes French lauzes and English stone slates. Like them, piode roofs are threatened mainly by cost, the scarcity of skilled craftsmen and the availability of suitable stone, and survive largely through heritage policy.

Sources and gaps

Typical slab thicknesses and roof weights per square metre: published information is limited.