Dinorwic Slate Quarry Workshops (Welsh Slate Museum Buildings)

This vast industrial complex, constructed of high-quality slatestone, forms a quadrangular plan around a central courtyard, longer on its east and west sides than on the north and south. The buildings date from the mid to late 19th century, with the giant water wheel installed in 1870 and various machinery additions continuing into the early 20th century.

Layout and Function

The north (entrance) range contains, from east to west, the engine and carriage repair shed, the chief engineer's house (now presented to the public in its circa 1911 form), and west of the entrance archway, the clerk's office and stores. The east range divides into four areas comprising, from north to south, an exhibition room, a reconstructed mess room (caban), and further exhibition rooms. The south range houses, from east to west, the maintenance workshop, sleeper grooving shed, vertical saw shed, engine shed, welding shed, and iron and brass foundry, with a first floor at the eastern end containing a store, pattern maker's workshop, and pattern store. The west range contains, from south to north, a store, blacksmiths' shop, repair shop, and fitting shop, the latter including a projection to the west. Approximately halfway along this range, projecting into the yard, stands the cropping machine shed. A short range at right angles to the western end of the south range contains a pattern store and links through to a circular saw shed running parallel with the south range. Directly adjoining the saw shed is the massive rectangular structure housing the giant water wheel. Access to the top of the wheel pit, formerly achieved by wooden staircase, is now via a 1990s steel staircase or by lift.

Construction and Materials

The buildings are predominantly constructed of high-quality, tightly jointed snecked slatestone. The eastern third of the central entrance block has a different appearance from the remainder, apparently resulting from repointing. Tightly-jointed voussoirs form the doorways and windows on the north elevation, while all other doors and windows, including those facing the courtyard, have slatestone lintels and quoins. The cropping machine shed uses slate slab construction. Slate roofs cover the entire complex: hipped to the central entrance block and cropping machine shed, pyramidal to the corner towers on the north front, and gable-ended to the remainder.

Architectural Character

Architecturally, the buildings present a dignified Classical form in plan and appearance. However, Gothic detailing is used throughout for the cast-iron windows, which were purpose-made for the structure in the foundry. This combination creates a distinctive and unique character.

External Elevations

North Elevation

The north elevation presents a symmetrical composition comprising a two-storey central entrance block flanked by high walls linking to square corner towers. The entrance block features a central round-headed archway with boarded double doors filling the lower section and a diamond-shaped slate clock directly above. Round-arched windows are symmetrically spaced, with two on either side of the archway on the first floor and in the outer bays only on the ground floor. A central timber cupola with bell and weathervane sits on the ridge, and tall integral end stacks with moulded capping stand at each end.

The left linking wall has a tall round-headed boarded door (to the carriage repair shed) on the left and a round-arched window to the right. The right linking wall has an identical window to the left and two grouped together in a round-arched recess on the right. Both corner towers feature octagonal louvres with spiked caps to their pyramidal roofs and three narrow round-arched windows on the upper floor. The eastern tower has a round-headed boarded door (to the engine shed) on the ground floor, while the western tower has paired round-arched windows in a round-headed recess at ground floor level.

West Elevation

The west elevation displays a tall round-headed arch with cast-iron window to the corner tower, with to its right a twin-gabled projection forming part of the fitting shop. The long range features smithy chimneys and ten tall integral lateral ashlar stacks with capping and slate pots—the leftmost isolated, the remainder regularly spaced. Blind panels appear in the wall, and two lean-tos stand towards the right end near the junction with the projecting gable of the south range. This gable has a wooden first-floor platform above the 4 foot (1.2192 metre) gauge railway track running alongside.

East Elevation

The east elevation shows blind panels to the long range, similar to those on the west side.

Wheel House

The wheel house is a tall rectangular structure with an iron water tank on top and a lower gabled building attached to its north side.

Internal (Courtyard) Elevations

North Side

The entrance block presents a symmetrical arrangement of two windows on each floor to either side of the central archway, appearing as three floors on this side, except for doorways to the inner bays on the ground floor—the left protected by a small gabled porch with adjoining lean-to, the right boarded with a narrow overlight. A small four-paned roundel sits above the central archway.

East of the entrance block, the gable end of the engine shed projects into the courtyard with a boarded door in the right corner. A low slate-slabbed structure with rooflights projects into the courtyard on the west side of the engine shed.

East Range

The single-storey east range comprises, from north, a window, door, window, door, three windows, door, four windows, door, two windows—all doors boarded and windows cast-iron. Slate ventilators sit near the ridge towards the southern end.

South Range

The two-storey south range has on the ground floor, from east, three boarded doors with narrow overlights, a wider doorway (for engines) with integral windows, and three further doors—the outer sliding, the central infilled. The first floor has seven evenly-spaced cast-iron windows. Four large rooflights appear near the ridge towards the western end, which projects beyond the west range. Squat integral end stacks complete this elevation.

West Range

The single-storey west range has, from south (left of the machine shed projection), a window, two doors, window, door, four windows, door. Under the projection are three windows, then to its right a further door, three windows, a door, and two windows. All doors are boarded double doors and all windows cast-iron. Three large rooflights align with the machine shed projection, with slate ventilators near the ridge immediately to their left.

The machine shed projection is open to both sides at the junction with the west range and has a further wide opening to the right on its southern side. A large rooflight occupies the eastern roof slope. A low gable-ended slate-slabbed shed abuts the south-eastern corner of the machine shed, with a boarded door and small four-paned window in its south gable end and a large rooflight in the eastern roof slope.

Courtyard

The yard is crossed by several 4 foot (1.2192 metre) gauge railway tracks, on which a variety of slate wagons are displayed. A large steam-driven crane stands to the south of the cropping machine shed.

Interior

North Range

Inspection of the engine and carriage repair sheds, belonging to Llanberis Lake Railway, was not possible at the time of survey. The chief engineer's house is presented to the public as it was fitted and furnished circa 1911 (until recently it served as the museum shop and provided staff accommodation) and also contains museum offices.

East Range

The east range is largely devoted to museum displays and has a reconstructed caban.

South Range

The foundry is dominated by a huge furnace, crane (dated 1872), and jib. A selection of patterns made of yellow pine are on display, along with a small brass founding furnace. A staircase leads to the pattern store and workshop. The sleeper grooving shed and vertical saw shed also retain their original equipment.

West Range

The area now demonstrating slate splitting and dressing was once part of the blacksmiths' shed and later a welding shop. Four hearths remain in the present blacksmiths' shop, all cast in the foundry, out of an original total of at least twelve. Racks of tongs, pincers, and swages are present, along with a forging hammer of circa 1900 and a pneumatic hammer of circa 1924. A large grinding wheel stands at one end, and strong, heavily-worn benches with vices attached run along the walls. Double doors lead to the cropping shed.

The fitting shop retains original machinery, including two lathes installed circa 1900.

The cropping machine shed projecting into the yard contains a combined punching and slotting machine, a cold saw, and a compressor—the latter not in situ and brought down from the quarry.

Saw Shed and Wheel House

South of the yard, the saw shed adjoining the wheel house retains original equipment and fittings, including circular saw, saw table, and pit. The wheel house itself contains the original huge iron water wheel, 15.4 metres (50 feet 5 inches) in diameter, built by the De Winton Company of Caernarfon in 1870. At the foot of the staircase to this wheel stands its replacement, the Pelton wheel installed in 1925 and still in use.