Ministry Of Defence Building L153 (Group D Incororating Mills)

ROYAL GUNPOWDER FACTORY TL3700 3/10021 MOD Building L153 (Group D Incorporating Mills) GV II*

Gunpowder Incorporating Mills. 1867-8, converted for cordite incorporation c1898-9; mid C20 additions. English bond yellow brick with hipped slate roofs to Engine House and Boiler House; cross wings have brick walls separating the bays which continue as coped gables breaking through the felt and slate roofs; mid C20 replacement walling to originally wood and canvas side walls. T-plan: central Engine House with 4-bay Boiler House at east end and 3-bay cross wings on its north and south sides for gunpowder incorporating mills. One storey, with taller Engine House to centre. Chamfered brick plinth and brick dentil cornice to Engine House and Boiler House. Boiler House of 4 x 1 bays, the bays articulated by brick pilasters and each originally with segmental brick arches over windows with blind rectangular panels below; the windows were sashes except in the westernmost bay on both elevations where they were blind, and have all now been replaced by larger mid C20 windows; east doorway widened and replaced in C20. Engine House has semi-circular arched window with keystone to upper part of each elevation (glazed to north and south, originally blind to east and west) and mid C20 inserted windows. Interior: Boiler House has 9 trusses with wrought-iron tension rods, king rods, and decorative cast-iron compression members. The Engine House carried a steam engine to drive the edge runners in the incorporating mills. Cross wings have composite timber and iron roofs, the relatively insubstantial fabric of both roof and walls being easily replaced should an explosion occur; a drenching apparatus, erected over each pair of runners, would also have been activated. The original gearing for the incorporating mills survives in a brick chamber below ground level. Cross-wing partition walls have cast-iron I-section girders and blocked openings in gables which belong to shafting for machinery which was probably installed for cordite manufacture. There was an open verandah along the west front. On the south side of the Boiler House was a coal yard containing a chimney at the centre of its wall. The building was served by a tramline to the west. Incorporation involved the combination of saltpetre, sulphur and charcoal to form gunpowder, the drive shaft and machinery transmitting power to the mills being passed underneath the building to minimise the risk of explosion. The incorporating mills each consisted of pair of large heavy edge runner, of iron, which revolved on a large circular bed. This mill is closely modelled on the earlier (1861) Group C Incorporating Mills, Building L157 (qv). (RCHME report, 1993).

Listing NGR: TL3771001232