Welsh & Spanish Slate; What’s the Difference?

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Welsh & Spanish Slate; What’s the Difference?

What is the difference between Welsh & Spanish slate; is possibly the most popular question we are asked at self-build shows across Ireland and the UK.  Other questions people frequently ask the LBS Team include Is local Welsh slate superior? Does Spanish slate pale in comparison?

Today’s post will cover the distinct differences between the two types of slate.

Spanish Slate Discoloration

Rusting & discoloured Spanish Slate

Spanish slate dates back to Ordovician period, roughly 400 million years ago. In comparison, Welsh Penrhyn slate is much older, dating back to the Cambrian era, which was over 600 million years ago. Essentially, Welsh Penrhyn slate has been inside the earth for much longer period of time, giving it very different properties than the younger Spanish slate.

Most notably, the Welsh slate’s age has made it denser, which means it is stronger and more durable. It is also much less susceptible to iron sulphide deposits, which are also known as pyrites. Spanish slates, however, are susceptible to pyrites, and in some cases where quality is poor, they can react in a way that causes rust, discolouration and disintegration. In time, these problems can result in slate roof failure.

In use today
Welsh slate has been used in Ireland for generations, and its distinct blue hue has become synonymous with the Irish landscape and many important governmental and ecclesiastical buildings. Because of its renowned strength, durability and distinctive colour, it has stood the test of time and garnered an excellent reputation. In addition to its unique and gorgeous blue hue, Welsh slate is renowned for being waterproof, highly resistant to extreme temperature fluctuations, acids, alkalis and UV light. Welsh slate can last hundreds of years. It can even be removed, redressed and reused many times, meaning it is more of a long-term investment.

Bangor Blue Slate, Welsh Slate, Purple Slate,

Welsh Slate Colours are Timeless

In comparison, the quality of Spanish slate varies widely. Because of the abundance of Spanish quarries, a huge amount of Spanish slate is imported to the UK and Ireland each year. Some of it is of poor quality, and some slate roofs that have been installed using Spanish slate have failed in mere decades. However, not all Spanish slate is poor quality. It simply depends on the Spanish quarry that has produced it. Thus, it is important to check the slate’s provenance and purchase Spanish slate only from reputable suppliers.

In conclusion
Generally speaking, some cheaper Spanish slate simply isn’t as resilient and durable as the eye-catching Penryhn Welsh slates. However, although some of the Spanish slate that is imported to Ireland the UK is less durable and more susceptible to rusting, discolouration and failure, quality Spanish slate does exist. You simply need to find a reputable supplier who sources from quarries with a reputation for excellence.

LBS understand the difference.
As Ireland’s leading supplier of slate, LBS source from the finest Spanish quarries and operate and own the renowned Welsh Penrhyn quarry. Whether you’d rather opt for durable Welsh slate or quality Spanish slate, we would be delighted to walk you through what we offer.

Click here to find out more from the LBS Team


Susan Burrows works for Lagan Building Solutions, based in Head Office, Lisburn, Northern Ireland – with 15 years experience in both the concrete roof tile and slating sectors.


LBS are owners of the Penrhyn Bangor Blue quarry in Wales and are Ireland’s largest independent supplier of natural slate and clay roofing products. They have offices in Lisburn, Dublin and Belfast and have a helpful friendly team of technical reps covering all 32 counties.