History in Structure

Former outbuilding of Plas Ynys Tywyn (attached to Co-op supermarket)

A Grade II Listed Building in Porthmadog, Gwynedd

More Photos »
Approximate Location Map
Large Map »


Latitude: 52.9257 / 52°55'32"N

Longitude: -4.1282 / 4°7'41"W

OS Eastings: 257033

OS Northings: 338595

OS Grid: SH570385

Mapcode National: GBR 5P.MRPN

Mapcode Global: WH55L.KQFG

Plus Code: 9C4QWVGC+7P

Entry Name: Former outbuilding of Plas Ynys Tywyn (attached to Co-op supermarket)

Listing Date: 1 April 1974

Last Amended: 26 September 2005

Grade: II

Source: Cadw

Source ID: 4429

Building Class: Industrial

ID on this website: 300004429

Location: Set back from the street and attached to the Co-op supermarket.

County: Gwynedd

Town: Porthmadog

Community: Porthmadog

Community: Porthmadog

Built-Up Area: Porthmadog

Traditional County: Caernarfonshire

Tagged with: Appendage

Find accommodation in


An outbuilding - probably a coach house - associated with Ynys Tywyn, the house and office built for John Williams, William Madocks' director of works for the Cob and later of Porthmadog harbour. It is shown on the 1842 Tithe map and is shown on the 1900 Ordnance Survey as part of a smithy. Now attached to a late C20 supermarket.


A lofted building of large slate-stone blocks laid in regular courses, and slate roof. The gable end has a bellcote over a replacement steel-framed small-pane loft window, beneath which is a similar but larger window. The L side wall has 3 open bays on slate-stone orthostats and lintels. In the R side wall is an inserted similar opening to make a pedestrian way through the building and enclosed within the open-fronted canopy across the Co-op supermarket, which is attached to the rear of the building.


Not inspected.

Reasons for Listing

Listed for its special interest as an early C19 building associated with the building of the Cob and harbour, notable for its distinctive use of local stone.

External Links

External links are from the relevant listing authority and, where applicable, Wikidata. Wikidata IDs may be related buildings as well as this specific building. If you want to add or update a link, you will need to do so by editing the Wikidata entry.

Recommended Books

Other nearby listed buildings

BritishListedBuildings.co.uk is an independent online resource and is not associated with any government department. All government data published here is used under licence. Please do not contact BritishListedBuildings.co.uk for any queries related to any individual listed building, planning permission related to listed buildings or the listing process itself.

British Listed Buildings is a Good Stuff website.