Description from record TQ 76 NE 110 :
(TQ 7603 6943) SAM No. 232 [former working Mast Houseand Mould Loft: scheduled]. (1) Construction of the building was authorised in 1753 as a mast house. A mould loft was incorporated into the design, creating an uniterupted working floor 55 ft x 119 ft. Six sawpits were excavated in the masthouse. The building was complete in 1755. (2)

The following text is from the original listed building designation:
TQ 76 NE CHATHAM MAIN ROAD
(East side) Chatham Dockyard
762-1/8/75
Former Mast House and Mould Loft
GV I
Mast house and mould loft, now museum. 1753-55, altered 1833. Weather-boarded timber frame and slate roof. PLAN: rectangular open plan with mould loft to 3 middle bays. EXTERIOR: single storey with second storey to middle 3 ranges, and attic to middle. Near-symmetrical range of 5 gables with a further W range, the middle one taller, with raking
.roof across to flanking bay above the mould loft. Ground-floor of continuos garage doors, and wide windows above with glazing bars. Middle range has 7 first-floor 6/9-pane sashes, and 5 attic 9-pane windows, flanking ranges have 2 first-floor 6/6-pane sashes. Middle range has large flat-headed dormers and 3 small ridge louvres, flat roof lights to other ranges, the end ones with 4 dormers.
INTERIOR: an extensive open internal space, the mould loft supported by large posts with diagonal and ships' knee braces, a king post roof to outer sections, and central mould loft floor with a 13-bay collared queen post roof.
HISTORY: used for shaping and storing masts on the ground floor, and for drawing out plans in the wide space of the first-floor loft. The mould loft was extended 1833 to include part of the flanking bays, and was used to layout HMS Victory in 1759, and HMS Achilles in 1860, the first all metal warship in the world. From 1855 it was used as a store.
The last surviving timber mast house in a naval yard, providing evidence in the joints and members of ship-builders' techniques applied to building construction, and part of a fine group of naval buildings within a complete Georgian dockyard.
(Sources: Coad J: Historic Architecture of Chatham Dockyard 1700-1850: London: 1982: 153 ; Coad J: The Royal Dockyards 1690-1850: Aldershot: 1989: 159-161 ; MacDougall P: The Chatham Dockyard Story: Rainham: 1987: 61).
Listing NGR: TQ7602569431 (3)

Additional reference (4)

<1> English Heritage 1:1250 SAM location maplet (OS Card Reference). SKE41612.

<2> Jonathan G Coad, 1989, The royal dockyards 1690-1850: architecture and engineering works of the sailing navy. No.1, Page Nos. 159-161, Plate Nos. 138-140 (Bibliographic reference). SKE6362.

<3> English Heritage, List of Buildings of Special Architectural or Historic Interest (Map). SKE16160.

<4> Coad, J., 1982, Historic Architecture of Chatham Dockyard 1700-1850 (Article in serial). SWX7760.