A museum which tells the story of how Welsh slate once roofed the world will see its new shop topped with metal, and a visitor shelter with corrugated sheets.

The National Slate Museum in Llanberis is located at the heart of the Slate Landscape of Northwest Wales in a UNESCO World Heritage location. Proposals submitted by Amgueddfa Cymru described internal and external alterations at the Grade I-listed Gilfach Ddu site, includng internal and external alterations, and was approved by the planning committee on 3 March.

The historic site was formerly the 19th century workshops of the Dinorwig slate quarry and has some of Britain’s best-preserved Victorian industrial buildings.

The proposal described how the existing shop was a circular shape but the new building would be square on the same footprint.

“It will have GRC cladding, namely reinforced concrete panels, coloured red with a grey metal roof. The windows and doors would also be in metal. Opposite the shop it is proposed to erect a new canopy that would function as a shelter for visitors. It will be in a square shape with a roof of red corrugated sheeting and the sides would all be open.”

The plans also noted new buildings had been “designed carefully” in relation to the existing site.

Cllr Gareth Jones said he was “supportive” of the application, especially regarding building a café and accessible facilities, but questioned why slate wasn’t used for the shop and visitor canopy roofs.

Planning officer Keira Sweenie said “sometimes excessive use of slate made new buildings more difficult to read and it will be easier to interpret as a modern addition rather than a traditional building”.

Cllr Elfed Williams said he had talked with Cllr Gwilym Evans and they have “no objection” to the plans, but asked for the character of the buildings to be maintained.