At Somerset Reclamation, we often get asked about the difference between Pennant and Lias stone — two types of local building materials commonly seen across Somerset and the West Country. Both have been used for centuries, but they’re quite different in how they were formed, how they look, and how they perform.
Geological Background
The key difference comes down to age and composition.
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Pennant is a Carboniferous sandstone, formed roughly 300 million years ago.
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Lias, on the other hand, is much younger — from the Early Jurassic and Late Triassic periods, around 180–205 million years ago.
That means Pennant is older, harder, and generally more resistant to weathering, while Lias tends to have a finer texture and can vary more in hardness depending on the layer.
Pennant Stone
Pennant is a hard, durable sandstone made mostly of quartz grains and fragments of other silica-based rocks such as schist and quartzite. It formed in high-energy environments like river channels and floodplains — areas with lots of erosion and sediment movement.
Because of this, Pennant is very dense and strong, making it ideal for building, paving, walling, and civil engineering. It’s often blue-grey, green-grey, or brown in colour, with a naturally riven or grainy surface.
That natural texture gives Pennant a distinctive, traditional look that suits both historic restorations and new builds looking for a bit of character.
Lias Stone
Lias is quite different. It’s a mix of limestone and mudstone layers, formed in warm, shallow seas full of marine life. The stone often contains fossils and has a high calcium carbonate content.
It’s usually blue-grey, sometimes with darker bands from the mudstone layers, and can be smoother and flatter than Pennant. While still durable, it can be softer in places and may require rendering or sealing when used externally.
Historically, Lias was also burned to make lime mortar, which was widely used in traditional building work across Somerset.
Which Should You Use?
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Pennant – Best for paving, external walling, garden features, and anywhere that needs strength and weather resistance.
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Lias – Suited to internal floors, walling, lime production, and areas where a traditional Somerset look is preferred.
Both stones have their place in local building and landscaping. Choosing between them often depends on the look you want and the job you’re doing.