Slate Flooring Tiles at Cardiff Central Library

Around 320m² of native Welsh slate has been used to create a high quality, durable floor for the reception area and main staircase at the new Central Library in the Welsh capital, Cardiff.

Specialist flooring contractor Vetter UK – a subsidiary of the project’s main contractor Laing O’Rourke – used the Dark Blue-Grey stone from Welsh//Slate’s Cwt-y-Bugail quarry to satisfy architect Building Design Partnership’s requirement for a traditional, durable finish.

Welsh//Slate is one of the world’s hardest-wearing slates and the 240 mm x 500 mm hand split riven tiles used at the new Central Library were ideal for the reception area with its heavy footfall.

The Welsh//Slate flooring tiles were fixed onto an 80 mm screed laid over the concrete floor slab and incorporating underfloor heating. “To accommodate any differential movement, we included 4 mm mastic-filled expansion joints in every 30 sq m of floor” says Mark Mooney, pre-construction manager with Vetter UK.

“The tile bedding was an unbonded system laid over a polyethylene membrane to allow the flooring to move independently of the concrete slab” continues Mr Mooney. “We included the expansion joints to coincide with the joints within the floor slab, with additional joints inserted to satisfy the requirements for a heated floor system”.

The 80 mm screed included an SBR47 additive to increase flexural strength and further resist cracking, explains Mr Mooney. The tiles themselves were fixed using PCI’s Floorfast 20 cement-based solid-bedding adhesive.

A proprietary sealant applied in several coats to the finished floor protects the slate against marking or staining, but no other surface finish was required to achieve the required slip-resistance.

“The riven finish has a natural slip resistance, but we still tested the product in three planes – it passed every test comfortably” says Mr Mooney.

As well as the floor, Welsh//Slate’s Cwt-y-Bugail tiles were used for the treads and risers on the staircase leading to the library’s mezzanine floor. Here, a polished aluminium nosing was introduced into the edge of every step to improve visibility, while the slate used for the risers has a polished, instead of riven, finish.