The following text is from the original listed building designation:
FAVERSHAM
TR 06 SW HAM ROAD
659/6/10014 Proof House approx. 10m SSW of Gate Ho
14-DEC-01 use, Marsh Works
GV II
Proof house at gunpowder works, disused. 1800-10. Brick with pyramidal slate roof.
PLAN: Square single-cell plan.
EXTERIOR: Segmental-arched doorway and flanking windows with sashes. Roof has a lantern on top.
INTERIOR: Not inspected.
HISTORY: The Marsh works were part of the Royal Gunpowder Factory which was established outside Faversham in 1786 after an explosion in the town, to remove some of the more dangerous processes. They played an important part in the improvement of British gunpowder leading up to and during the Napoleonic Wars, under William Congreve. The saltpetre refinery which was built in 1789 as part of Congreve's successful drive to improve the ingredients of British powder. This included dedicated proof houses, the first of which were built in 1804, and this is probably the oldest example. It was privatised after the war, and closed in the 1920s.
The proof house, a type of laboratory for testing powder by flashing it, was added in the early C19 refurbishment of the refinery. The roof lantern was intended to admit light and let out the fumes. Associated with the late C18-early C19 saltpetre refinery at the Marsh Works (qv), the best preserved of this type in the country and comparable with French and Swedish examples.
(Wayne Cocroft, Dangerous Energy. The archaeology of gunpowder and military explosives manufacture. Swindon (English Heritage), 2000, pp. 54-67)

In 2019 an historic building recording of the former Marsh Gunpowder Works buildings now situated within the former Oare Mineral Works, Faversham, Kent was completed in advance of works to the designated and non- designated heritage assets. (2)

<1> English Heritage, List of Buildings of Special Architectural or Historic Interest (Map). SKE16160.

<2> Headland Archaeology (UK) Ltd, 2019, Historic Building Recording of the Marsh Gunpowder Works within the Former Oare Mineral Works, Faversham, Kent (Unpublished document). SKE54278.