A mid-nineteenth century slate warehouse, depicted on an 1871 estate map, built on Oakeley's Wharf (nprn 34160). It is a long, low building, stone walled with a slated gabled roof; the east side was originally open, divided into ten bays by coursed stone piers. The building now houses the Porthmadog Maritime Museum where ship models, pictures, documents, tools and other equipment show the importance of local shipbuilding and the export of Welsh slate in the fine Porthmadog topsail schooners.
The slate shipping manager's house and office (nprn 16619) adjoin on the north.
RCAHMW, 30 September 2010.