Barn and Two Adjoining Engine Houses Approximately 10 Metres North of Trewithen Farmhouse

This is a barn with two adjoining engine houses, located approximately 10 meters north of Trewithen Farmhouse. The barn dates from the 18th century, while the horse engine house was built around 1800, and the steam engine house was added in 1811. The structure features Flemish bond brickwork over a stone plinth and has a hipped roof made of Delabole slate. It is a rectangular barn with a horse engine house at the rear and a steam engine house in the angle, both of which are two storeys high and consist of six bays. The barn has slightly arched openings and dove holes beneath wide eaves. The south end wall includes a flight of granite steps with an iron handrail leading to a loading door.

Inside the main barn, there is a pegged tie beam and collar rafter roof structure. The steam engine, which was installed for Sir Christopher Hawkins in 1811, was designed by Richard Trevithick and built at the Hayle Foundry. This engine is notable for being the first steam engine made for threshing and is recognized as the earliest surviving agricultural steam engine in the world. It is currently stored at the Science Museum in Kensington. The engine was exhibited at the Royal Agricultural Society Show in Kilburn in 1879 and was presented to the Science Museum by the Royal Agricultural Society that same year. The Trevithick engine is a single acting high pressure non-condensing steam engine, with a boiler that is a later replacement, possibly from 1854.