: Slate Development

As the National Slate Museum continues its major redevelopment programme, an important community of residents remains very much at the heart of our plans - our bats! 

Working closely with ecologist Carola Hoskins of SK Environmental Solutions ltd, we’ve been carefully monitoring and protecting ten known bat roosts across the site. 

These roosts are home mainly to common and soprano pipistrelle bats, two of the smallest bat species in the UK. 

Seven of the roosts are used by individual males or non-breeding females, but one is particularly special - a soprano pipistrelle maternity roost that supports around 65 bats at its Summer peak.

A Safe Place for New Life

Although the colony is currently winter hibernating elsewhere, by late April the bats will begin to return. 

At this time around 35 females will settle into the maternity roost and by late May or early June, each Mother gives birth to a single pup doubling the colony size almost overnight. While 65 bats might sound like a lot, it’s a relatively small maternity colony for soprano pipistrelles, making every individual important.

One of Nature’s Cleverest Adaptations

“Bats have many remarkable traits, but one of the most fascinating is delayed fertilisation." said Carola. "Female bats mate in autumn, but they delay pregnancy until spring, storing sperm through the winter months. This ensures that pups are born at exactly the right time when warmth, food, and safe roosting conditions give them the best chance of survival. It’s one of the many reasons these tiny mammals are so well adapted to life in the UK."

Conservation at the Heart of Our Redevelopment

Because bats and their roosts are legally protected, all redevelopment work involving the roofs at the Naional Slate Museum or potential bat habitat is carried out under licence, and only during winter while the bats are away. 

Carola is working alongside our Museum and Construction teams to guide every step of this process, by ensuring that roost entrances remain open, structures remain suitable, and the bats can return safely each spring.  This careful approach allows us to progress with essential redevelopment while safeguarding a species that has lived alongside the museum buildings for generations.

The National Slate Museum redevelopment project is funded by The National Lottery Heritage Fund, UK Government via Cyngor Gwynedd as part of the Llewyrch o'r Llechi project, Welsh Government including the Community Facilities Programme, the Wolfson Foundation, Garfield Weston Foundation and other funders. We are extremely grateful to all our funders for their support.      

National Slate Museum Slate Quarrymen swap Industrial workshops for Castle splendour!  

For the first time in history slate quarrymen are working at Penrhyn Castle – the home of one of the wealthiest Slate Quarry owners in North Wales.  

Our demonstrating Slate Quarrymen, who usually hold demonstrations at the Museum in Llanberis, are instead demonstrating their skills and craftsmanship at the Castle.  

This astounding turning point comes as we are temporarily close to the public for redevelopment but we didn't want to stop telling our story so decided to take our story to other locations important to the story of slate and which are part of the World Heritage designation for the Slate Landscape of Northwest Wales.  

Penrhyn Slate Quarry established by the Pennant family, dominated the Welsh slate industry for almost 150 years and was notorious for its harsh working conditions. In 1900, over 2000 workers went on strike for better wages and working conditions - a culmination of several years of dissatisfaction and unrest. 

Known locally as the Penrhyn Lockout, the strike lasted for over three years and was one of the longest and most bitter industrial disputes in British history. It caused incredible hardship for the Quarrymen and their families and ripped apart a community, dividing it into strike ‘faithful’s’ who remained on strike or left to find other work elsewhere, and ‘bradwrs’ (traitors) who returned to work. 

Many in the local community still regard the Castle as a symbol of wealth and oppression. Historically, Quarrymen would not have crossed the threshold to the Castle and many of their families have struggled to do so since then. 

Now managed by National Trust Cymru, Penrhyn Castle and Garden have been working with artists and the local community for over a decade to share more about this history and re-engage with its local community as Ceri Williams, General Manager at Penrhyn Castle explained: 

“Over the last decade and more we’ve been working to re-address the way we share our industrial and colonial connections at Penrhyn Castle. Each year, we've achieved new milestones, but welcoming the Quarrymen into the castle marks a significant leap forward in reconnecting the community with this historic site. 

Already, crowds have been gathering to catch a glimpse of the live slate-splitting demonstration that not only celebrates local craftmanship but provides authentic experiences that resonates with the castle’s industrial history. As we continue to work with the National Slate Museum over coming months, we look forward to combining our offers and providing visitors with a unique and memorable visit to Penrhyn Castle.”

For us, the opportunity to have our Quarrymen demonstrating at Penrhyn Castle is a key feature of our redevelopment programme - in particular our Museum on the Move campaign in 2025 as Elen Roberts, Head of the National Slate Museum explained: 

“We’re very grateful to the team at Penrhyn Castle and to National Trust Cymru, for giving us this unique opportunity to work with them as part of our redevelopment programme for the National Slate Museum.  We’ve worked closely with the Trust over the years to share the story of slate and this opportunity to share our Quarrymen’s skills and stories is an enormous thing from both sides. Relocating here – and to other sites around the World Heritage designation during our Museum’s redevelopment - will allow us to engage with new audiences and ensure our story continues beyond the walls of the museum. 

Our staff will benefit from continuing to interact with the public which will enhance their knowledge of the slate story, and hopefully visitors will benefit from encountering Museum staff in new locations – which, alongside the National Trust’s existing offer to visitors at Penrhyn Castle, will offer a fresh perspective on the story of slate”

Both attractions are key parts of the World Heritage Site for the Slate Landscape of North West Wales. Lord Dafydd Wigley, Chair of the Llechi Cymru Partnership welcomed the development:

“Cyngor Gwynedd and its partners have worked together over many years to develop a strong partnership to deliver the Slate Landscape of Northwest Wales World Heritage nomination and subsequent inscription. The results of this strong and active partnership is now bearing fruit as we not only see significant investment of over £30m through the Llewyrch o’r Llechi programme of activities - such as those at Amgueddfa Lechi Cymru and others across the Slate Landscape; but we are also seeing new and innovative ways of working together to reach new audiences, provide new experiences and to share our monumental and global story of how north Wales roofed the world.”

The Quarrymen are at Penrhyn Castle on a daily basis during 2025.                                         

For more information about the history of Penrhyn Castle visit www.nationaltrust.org.uk/penrhyn-castle-and-garden

I know, archaeology is not something you would automatically associate with the Slate Museum – it’s usually geology! But in December, three volunteers joined us to take part with the archaeological surveying required for the enabling works of the redevelopment project at National Slate Museum, Llanberis.

Archaeology Wales were commissioned to survey and record two features at the Gilfach Ddu workshops, where the museum is based. They were recording a post-1970s staircase in the Foundry, and original railway tracks outside in the yard. This surveying is required due to the Gilfach Ddu workshops being a listed building, and to ensure anything changed during the redevelopment project is recorded. The staircase is being replaced with a more accessible and safer design, whereas the railway tracks will be replaced once drainage has been installed beneath them. 

Three volunteers, Nicola, Donna and Shay, joined buildings archaeologist Emily to draw and photograph these features, creating a permanent record for the future. This provided volunteers with a good base of knowledge of buildings archaeology and how to survey features by drawing and photographing. It also gave a great opportunity to learn about the Slate Museum redevelopment and the improvements being made. 

DIOLCH Nicola, Donna a Shay! 

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The project is funded by The National Lottery Heritage Fund, UK Government via Cyngor Gwynedd as part of the Llewyrch o'r Llechi project, Welsh Government including the Community Facilities Programme, the Wolfson Foundation and The Garfield Weston Foundation and other funders. We are extremely grateful to all our funders for their support. 

It's been an extraordinary twelve months for the National Slate Museum Redevelopment Project. 

Since we temporarily closed our doors in November 2024, the team has undertaken the incredible feat of preparing the museum for redevelopment. 

We've been successful with a hugely ambitious £12m grant from the National Lottery Heritage Fund. This, together with the investment from our other supporters, has finally enabled us to realise the full ambition of the project.  

We've safely packaged  and moved our collections to their temporary home at Llandygai Collections Centre and we've appointed MPH Ltd as lead contractor and started the exciting and highly specialised work of conservation and repair on site. 

During the enabling works phase, we've seen the demolition of the old shop and café buildings in preparation for the new developments on site. It has been incredible to see these parts of the site temporarily returned to how they looked when the workshops were in operation.

Our staff and collections have taken the museum experience beyond the museum walls into partner locations across the World Heritage Site with our ambitious 'Museum on the Move' campaign. Some of our staff are located at the Quarry Hospital here in Llanberis where we've introduced a new Museum character - Margaret the Matron!  Our slate quarrymen have made themselves at home in their temporary location at Penrhyn Castle, a powerful and symbolic moment for the story of slate and its place in the history of our local communities here in northwest Wales. Our Blacksmith meanwhile has a space at Crefft Migldi Magldi in the slate quay in Caernarfon working alongside another young Blacksmith. 

We've also been working very hard on designs for some of the key areas for reinterpretation in the Museum which has been very exciting. 

Below is a list of some of the things that have taken place thanks to the dedication of our extraordinary team and wider partners. 

• 123 people attended our Silent Spaces Tours of the Museum before closing. 
• 27,643 people have visited our semi-permanent locations
• We’ve been to 19 community events where we’ve met and engaged with 1068 people. 
• 1,115 children have enjoyed our digital and in person Learning activities including the Quarryman’s Day, the waterwheel challenge and 'Strike!' 
• We used 1,734 cable ties to label all the original nails in the walls of the Museum. 
• 165 objects have been boxed up at the Museum to protect them from damage.
• We've packed away 13,208 objects to our new collections centre in Llandygai by 
• The collections team have hosted 13 visits to the Llandygai Collections Centre and provided guided tours to 119 people.

It feels like a good time to pause, reflect and celebrate what we have achieved over the last year but the pace of the project shows no signs of slowing! 

Over the next two years we will continue to evolve the visitor experience on site including the exhibitions that will define a truly world-class gateway to the world heritage site of the Slate Landscapes of North-West Wales alongside our partners across this special region. Watch this space!