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Spanish, Canadian, Welsh – Which Slate is Best for Your Roof?

It’s universally acknowledged that Welsh slate is the best quality. So good in fact, that a Welsh friend who recently migrated to Australia says her slate roof was stolen from her garden back home in Wales after it was removed for repairs!

The repairs to her roof were not to the slate itself, but to the underlying structure that holds it in place – in this case the felt underlay. That’s because one of the key attributes of a slate roof is that it can last a century before the tiles need replacing.

One of the natural attributes of slate is that it is absolutely impermeable to water. This means that even in freezing conditions it will not crack or expand. The most common damage that occurs to slate is either storm damage, where strong winds have loosened a tile, or direct damage from humans – walking on a slate roof to retrieve a ball, for example.

Although Welsh ‘Penrhyn’ slate is highly desirable, it’s also expensive. So it pays to look at other options for your slate roofing. Here are the different properties of slate from three countries: Spain, Canada and Wales.

Spanish slate

Spain is the world’s biggest producer of slate, one company alone accounting for a quarter of the world’s supply with 16 quarries and 22 processing plants.

Spanish slate can vary tremendously in quality. At the cheaper end of the range the slate is soft, which means it weathers down quickly, and it contains undesirable iron pyrites.

Slate is formed when clay undergoes pressure and the resulting rock contains microscopic particles of minerals including quartz and mica, plus many other minerals. Pyrite is formed when iron is present in the slate. It eventually rusts, covering the roof in undesirable brownish stains. It is possible to identify pyrite in slate using x-ray diffraction.

But at its best, Spanish slate rivals that of Wales. ‘Forna’ slate is acknowledged in Europe as one of the best; ‘Cafersa’ is another quality Spanish slate with no iron pyrites and a hundred-year guarantee from the quarry.

Canadian slate

Canadian slate has a good reputation in the industry and because of its blue-grey and heather purple shades can be used as a substitute for Welsh slate. ‘Glendyne’ is a popular blue-grey slate from the town of Saint Marc du Lac Long in Quebec that closely resembles Welsh slate. It is also free from iron pyrites and metallic intrusions so it won’t rust and is not affected by UV light or acid rain.

More and more Australian slate companies are using Glendyne slate as an alternative to the slates of North Wales. With a 75 year guarantee from the quarry, and a reputation for consistency that Spanish slate can’t match, Canadian slate could be the roofing material for you.

Welsh slate

The slate quarries of the Ogwen-Cegin valleys in North Wales, including the famous Penrhyn quarry, are so renowned for their slate production that the area is being considered by UNESCO for World Heritage Listing.

Although slate was quarried here as far back as Roman times, it was the Industrial Revolution that saw Welsh slate rise to prominence. Transport technology devised in Wales was used by slate mines throughout the world.

Penrhyn slate is blue/purple and can last more than a century. It is easy to work with and requires little maintenance. If it is more expensive than other types of slate, it can also be found through reclamation – unlike many roofing materials, slate can be recycled.

Penrhyn Heather Blue is perhaps the best known of the Welsh slates, as well as the dark blue-grey from the Cwt-y-Bugail quarry. These slates are known to have no iron pyrites in them and do not fade, presenting a sought after finish.

So if you’re looking to do slate roof repairs in Sydney or are keen to explore the possibilities of slate roofing for your home, contact First Class Slate Roofing for their expert recommendations.