Giacomo Gotti, finishing a stone roof in Vallemaggia.
is originally from Bergamo, Italy, and has been working for a construction company in Ticino for 40 years and is a true master of the art of building stone roofs. He and his colleague from Ragusa, Angelo Dibartolo
, just finished building a 70 square meter stone roof in Vallemaggia. As they were laying down the last pieces of rock, I asked them about the process and secrets of building a stone roof. “First, you have to order the stone slabs or piode
. The steeper the roof, the less deep the slabs need to be. Usually stone roofs have an inclination of 70-80%, otherwise the slabs are too deep and the roof becomes too heavy and expensive. Then, the front side of the piode
needs to be shaved off so that the water will run off them and not enter the roof. We call this sbarbare
, which literally means ‘to shave’, and it is done by hand.”
Once the stones have been prepared, they are laid on the roof starting from the bottom layer, also called gronda. The slabs of this first layer are wider than the rest (about 60 cm). The second layer, called terza, is different from all the others in that the stone slabs are rounded, almost in an oval shape. “This is done mainly for esthetic reasons,” says Mr. Dibartolo. “It’s actually the old way of building roofs and nowadays not everyone does this anymore.” After that, the layers continue regularly. “Every other layer,” adds Mr. Gotti, “the stones are set on a piece of larch, which gives the roof its slant. In dialect we call this tampiara. Larch is used because it does not swell or withdraw when it gets wet.” The stone slabs set on the tampiara are deeper than the stones of the layer on top of that. The last stone of each layer, at the two ends of the roof, is called cimosa. The cimosa is worked on three sides: on two sides it’s shaved, so the water runs away from the roof, and on third side it’s rounded for aesthetic reasons. The very last layer, at the top, is called colmo and is once again made of wider slabs (about 60 cm). This layer is shaved on two sides, in opposite directions. “At the very end,” says Mr. Gotti, “we add a line of cement between the colmo and the layer of stones beneath it, to seal off the roof. This is the only cement we use.”
Building a stone roof is very labor intensive, especially without the aid of a crane. “I take a lot of satisfaction from building stone roofs because they are eternal,” says Mr. Gotti, “but the work is much easier with the aid of a crane. I’ve built many roofs up on the mountains, where I’ve had to carry every stone up the roof on my shoulders. That’s really hard work!” Mr. Gotti first learned to build stone roofs when he was 15, by helping his older co-workers, who taught him this ancient art. “The most important thing,” he says, “is to be patient and precise—not to hurry. If a stone moves even slightly, take the time to stabilize it with a chip.” Several factors influence the time it takes to build a stone roof, such as the presence of a crane and the quality of the stone slabs. Some slabs can even be recycled from the original roof, if they are still in good shape, although in most cases only 15-20% of the original roof can be re-used. “It took us about two weeks to build the last roof we did, but the stones didn’t need much work, except shaving, and we also had a crane.” One square meter of finished roof weighs about 500 kilos and costs about 700 francs (800 including insulation).
All of the stone roofs in Ticino are made from granite. The support structure of the roof, instead, is made from wood, with a steel ridge beam at the top. “In the past,” says Mr. Gotti, “they entire support structure was in wood—even the rafters were held together with wooden nails, which in dialect we call paricc.” Stone roofs are expensive and labor-intensive, but as Mr. Gotti says, they are eternal. If well made, a stone roof can last hundreds of years, requiring little to no maintenance.
Traditional wood roof structure, held together with wooden nails (paricc).
A new structure, with a steel ridge beam.
The stone slabs (piode) fresh from the quarry.
Giacomo Gotti setting the second layer (terza) of slabs, which are slightly rounded, the old-fashioned way.
In this example, you can clearly see the rounded second layer of stones.
Every other layer of stones is set on a piece of larch (tampiara).
The cimosa, shaved on two sides to prevent the water from running down the side of the building or into the roof, and rounded on one side for aesthetic reasons.
Angelo Dibartolo laying down one of the last rows.
One side of the colmo, where the only cement is used.
For those of you who read Italian, here is a technical description of traditional roof building techniques and materials in North-Western Italy: “Il peso della tradizione”.