Llechwedd Slate Quarry floor 7 mill is a two-bay functioning slate mill of 1935, which exemplifies the end of the tradition of building the traditional slate mill that can be traced back to the 1850s and the Diffyws Quarry mill (NPRN 415671). The floor 7 mill is traditional in having a slate roof but is innovative in its use of steel as a constructional material.   

A functioning slate mill on floor 7 of Llechwedd Quarry, constructed in 1935 to the design of the quarry engineer, Captain Williams Ellis. Though it has a slate roof, its framework is of steel and the walls of corrugated iron. It was built for electrical operation of the saw tables, and now functions with modern processing plant. It forms a prominent skyline feature for visitors to the quarry’s visitor-attractions. 

The mill is now served by road lorries; the inclined plane which formerly hauled slate and waste rock out of the workings is disused but the gable profile of the winding house forms part of the prospect of the horizon. 

Sources:  

• Louise Barker & Dr David Gwyn, March 2018. Slate Landscapes of North-West Wales World Heritage Bid Statements of Significance. (Unpublished Report: Project 401b for Gwynedd Archaeological Trust)

Hannah Genders Boyd, RCAHMW, February 2022