Vermont Purple Slate is a natural roofing material set to redefine heritage and conservation roofing projects across the country.
Vermont Slate Geology
The Slate Valley of Vermont is unique in the world because of its formational history. Metamorphism of shale into slate and the different cooling temperatures acted to make many different colours of slate in this very small area. It is world-renowned for this fact.
The slate in this region has been formed between 450 and 650 million years ago during the Cambrian and Ordovician Periods of the Palaeozoic Era.
The reason why slate is so widely dispersed throughout the world is due to plate tectonics. At one time, every continent on the earth was combined into one major landmass, Gondwanaland.
The relevant fact is the incredible similitude between the purple slate of Vermont and the purple slate of Wales!
There are 5.000 km between the 2 quarries but they’re similar:
Because the continents were all joined together, there were shared areas of similar rock formation.
For example, the slate in Vermont and New York has similar formation times and characteristics to the slate from Wales.
Nowadays, the Slate Valley is a large area that covers parts of two different states. It is in Rutland County, Vermont and Washington County, New York. Overall, it measures approximately thirty miles from north to south and about ten miles from east to west, a total area of about 300 square miles.
For centuries, the Welsh Blue Bangor slate has been the benchmark for quality and aesthetics on Ireland’s most cherished buildings. Now, SIG Roofing is providing a direct and certified equivalent that offers the same unique beauty and performance required for both sensitive restoration and new premium construction.
The Unmistakable Equivalence: Vermont Purple vs. Welsh Blue Bangor
The traditional Welsh Blue Bangor slate, quarried from Penrhyn, is renowned for its “Heather Blue” or “Penrhyn Purple” colour—a sumptuous, unfading purple with subtle, dark plum tones. This distinctive s
hade has graced iconic buildings worldwide, including St. Patrick’s Cathedral in Dublin.
Vermont Purple Slate is sourced from the prestigious “Slate Valley” region of Vermont, USA, which shares a geological kinship with the Welsh quarries. The result is a slate that delivers a near-identical aesthetic and technical profile:
Colour Match
Vermont Purple is a majestic, unfading deep plum/burgundy that perfectly mirrors the famed ‘Heather Blue’ appearance of Penrhyn slate. It often includes occasional minor green markings, adding to the unique, natural character—a look long associated with traditional Welsh slate roofs.
Technical Performance: Vermont slate is consistently tested to the highest European standards (BS EN 12326), achieving top-tier classifications (often A1, S1, T1 and W1). This rigorous testing ensures its technical properties are comparable to Welsh slate, guaranteeing outstanding:
- Durability and Strength: With a predicted service life of a century or more.
- Low Water Absorption (W1): Crucial for preventing freeze-thaw damage in the Irish climate.
- Resistance to Thermal Cycling (T1) and SO2 Exposure (S1): Ensuring its rich colour and integrity are maintained over time.
For architects, conservation officers, and homeowners, this equivalence means that Vermont Purple Slate can be specified with confidence as a technically and aesthetically faithful alternative to the traditional Welsh slate for all heritage work.
Quality and Appearance: The Vermont Advantage
Unfading Beauty
Vermont Purple is classified as an Unfading slate. This is a critical distinction, meaning the colour will remain true and vibrant for the life of the roof, unlike ‘weathering’ slates which change colour significantly over time. The deep, rich purple/plum hue, sometimes mottled with striking green inclusions, ensures the roof will be a timeless architectural feature.
Benefits
Vermont slate is exceptionally dense, tough, and durable. Its robust properties make it an outstanding choice for the harsh, rain-swept Irish environment:
Consistency and Availability
Through SIG Roofing, the Vermont Purple Slate is available in a variety of traditional and contemporary sizes (e.g., 508 x 305mm, 500 x 250mm). This ensures ease of installation and the ability to match existing roof patterns on restoration projects.
The Ideal Choice for Irish Heritage
By launching the Vermont Purple Slate, SIG Roofing Ireland is offering the market a proven, premium, and reliable alternative to the traditional Welsh slate, backed by a robust warranty of up to 75 years.
The aesthetic integrity, unmatched durability, and superior technical performance of Vermont Purple Slate make it the logical and compelling choice for all conservation and premium new-build projects seeking the timeless beauty of a purple-toned, high-performance natural slate roof.
Embrace the heritage aesthetic and secure the future of your roof with Vermont Purple Slate.
The Old National School, Cluain Fhia Paorach, Holycross — a heritage restoration project
Tramore Railway Station — an example of Vermont Purple Slate in a conservation setting.
Contact us today to discuss your project or to request a sample.
