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Cof Cymru: National Historic Assets of Wales · Wales

Dam to SW of former Felin Fawr Slate Works

Llandygai, Gwynedd, Wales

The record

Designation
Listed building, Grade II
Broad class
Industrial
Date of designation
26 July 2001
Locality
Coed y parc
Community
Llandygai
Unitary authority
Gwynedd
Country
Wales
Coordinates
53.17476, -4.07489
Cadw reference
25606

Slide toward Today to fade the historical sheet and see the modern map underneath.

David Rumsey Map Collection, Stanford Libraries

Shown on 5 historical map sheets, the earliest the 1896 "Sheet 7. Ordnance Survey of England and Wales." (David Rumsey Map Collection, Stanford Libraries).

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This record in Cadw's own full report ↗

Cadw's description

The dam is the upper of two once-similar structures across the Galedffrwd, retaining a reservoir to the NW of the lane leading to Mynydd Llandegai, SW of the former slate works.

The Felin Fawr Slate Works complex was established at the beginning of the C19, serving the Penrhyn Slate Quarry - an early example of an industrialised slate sawing and dressing site relying on water power. The earliest surviving water-power system at the site (comprising a pair of dams forming a reservoir on the Galedffrwd, and a water wheel) appears to date from 1846-1848, associated with an early campaign of improvement on this key site. The lower of the two dams has been altered in recent years, but the upper dam remains virtually intact. The resultant reservoirs ultimately provided the water to operate both water wheels on site, together with a later turbine.

High dam wall constructed from massive slate blocks. The wall is roughly coursed and slightly battered, built on a slight curve across the valley floor. Two cast-iron sluices, and a brick-lined spillway in the centre of the dam wall. From the base of the dam, are the remains of 4 cast-iron pipes partially supported on a stone causeway, which formerly took water downstream to various areas of the slate works site.

Listed as a fine mid-C19 masonry dam, an important component in the exceptionally complete surviving water-powered slate works at Felin Fawr.

Nearby in the register

Other entries of the same register within about three miles of this one, by straight line.

Designated Historic Asset GIS Data, The Welsh Historic Environment Service (Cadw), 2026-09-07, licensed under the Open Government Licence http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ Cadw, the Welsh Historic Environment Service · Open Government Licence v3.0
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