Knapsack Viaduct, Lapstone | NSW Environment & Heritage

Culture and heritage


Knapsack Viaduct, Lapstone

Item details

Name of item: Knapsack Viaduct, Lapstone
Other name/s: RTA Bridge No. 967
Type of item: Built
Group/Collection: Transport - Land
Category: Road Bridge
Location: Lat: -33.75861111111111 Long: 150.64027777777778
Primary address: Great Western Highway (former alignment), Lapstone, NSW 2773
Local govt. area: Blue Mountains
All addresses
Street AddressSuburb/townLGAParishCountyType
Great Western Highway (former alignment)LapstoneBlue Mountains   Primary Address


Organisation NameOwner CategoryDate Ownership Updated
Roads and Maritime ServicesState Government 

Statement of significance:

The Knapsack Viaduct has a high level of historic, associative, aesthetic and technical significance at the State level. It is an impressive and attractive structure which is highly articulate about the technical challenges involved in the construction of the rail across the Blue Mountains, the high level of technical achievement embodied in Whitton's design and the construction of the line and the interaction between the railway and the landscape. As a key component of the line, the viaduct contributed to the economic and social development of the Blue Mountains and the agricultural areas and settlements to the west of the range. The viaduct is held in high esteem by the local community, railway enthusiasts, and the wider community, amongst whom there is widespread recognition of its historic, associative, aesthetic and technical qualities. The viaduct has rarity value as probably the most impressive structure of its type, as well as the capacity to represent the key characteristics of the small class of similar structures built in association with the railway projects of the nineteenth century.
Note: The State Heritage Inventory provides information about heritage items listed by local and State government agencies. The State Heritage Inventory is continually being updated by local and State agencies as new information becomes available. Read the OEH copyright and disclaimer.


Designer/Maker: John Whitton - NSW Railways
Builder/Maker: W Watkins
Construction years: 1863-1867
Physical description: In John Whitton's words, the bridge 'consisted of five spans of fifty feet and two of twenty feet each, built in masonry . . . for a single line of railway on an incline of 1 in 30'. This primary description failed to convey the majesty of the block sandstone viaduct sweeping across Jamisons Creek, a deep sandstone gully, with maximum pier heights of 38m, and excellent stonemasonry. The tall ribbed piers taper with height and are topped with classical semi-circular sandstone arches built on corbels at the spring lines. The current configuration incorporates sandstone faced reinforced concrete cross beams at each pier which cantilever to support a reinforced concrete road deck edged with sandstone faced parapets. This current deck has a road width of 30 feet (9.1m). The bridge terminates in traditional sandstone abutments which have been widened to accommodate the revised road width. The bridge now sits on a disused road, but services a pedestrian/bikeway which has been constructed along this old road alignment
Physical condition and/or
Archaeological potential:
The bridge is in very sound condition. The general condition of the sandstone appears good. However, much of this has been surfaced with different types of surface preservative which render the original colours rather unnaturally. Presumably this surfacing was installed as a result of some fretting of the sandstone. There is also some evidence of leaching/staining on the underside of the arches. This is unlikely to be of structural consequence. Having started life as a rail bridge as part of the zig-zag up the Blue Mountains, the bridge is part of a system of grades which have progressively developed to provide higher level s of service and safety. Remnants of old cuttings, culverts etc may be observed on these alignments.
Modifications and dates: 1913 - relieved of railway traffic
1926 - The bridge was adapted for use as a road bridge, the inside faces of the parapets were trimmed, and resurfacing would have been necessary.
1939 - widened to 30ft by means of a reinforced concrete cantilevered deck.
1993 - relieved of road traffic Pedestrian/cycleway path installed post 1993
Current use: Road bridge
Former use: Rail Bridge


Historical notes: The Knapsack Viaduct was designed by and built under the direction of John Whitton, second Engineer-in-Chief for Railways. Its purpose was to carry the original Western Railway Line across Knapsack Gully at the head of Jamison Creek. It formed part of the Little Zig Zag, which climbed the eastern escarpment from Emu Plains to today's Glenbrook. Whitton repeated this Zig Zag to descend the western escarpment of the mountains, incorporating similar stone viaducts. The Victoria Bridge across the Nepean River at Penrith was also designed by Whitton as part of the same programme, as were the Springwood Railway Station (1884) and the Bowenfels Railway Station Group (1869). (Palmer, n/d p. 10)

The building of the railway over the mountains was a major design and construction undertaking. Three possible routes for the line were investigated. A route following Bells Line of Road via Mount Tomah was discarded as it was considered too steep, and a second possible route through the Grose Valley was deemed unsuitable due to the unstable terrain. The third route was favoured by Whitton and follows the approximate route of the final line. Various methods of ascending the Lapstone Hill were suggested to Whitton including a horse tramway laid on existing roads, which the then Governor, Sir William Denison, advocated for the whole of New South Wales. Passengers would leave the tram at the bottom or top of a hill and walk up or down as required. Another suggestion, proffered by the Rev. Dunmore Lang also suggested that passengers walk up or down the hill on a long staircase while a stationary engine at the top or bottom of the escarpment lifted and lowered goods. Whitton himself would have preferred to make use of tunnels to achieve the ascent of Lapstone Hill, but was forced into compromise by the limited funds made available for the project. The little Zig Zag, presenting steeper grades than Whitton would have liked, and Knapsack Viaduct resulted. (Rowland, 1954, pp. 249-50; Blue Mountains Historical Society Inc, Correspondence, 14 July, 2004; P. Belbin & D Burke, 1981, p. 38)

The contract for construction of the Knapsack Gully Viaduct was let to W. Watkins in March 1863, who also completed the stone piers of the Victoria Bridge at Penrith, also constructed as part of the railway project. Work was completed in 1865. The bridge was constructed of sandstone quarried in the neighbourhood, and carried a single rail line. (Palmer, n/d p. 10) The construction of the railway brought hundreds of people to Lapstone, and later, employees of the railways to service it. The construction workers camped near their work sites, often with their families, although the exact locations of the camps are not known. (Aston, 1988, p. 12)

Traversing the Lapstone Zig Zag by train was a distinctive experience. Ascending or descending, the trains travelled forward on the top and bottom 'roads' and backward on the middle one; at each junction the train paused in a 'Dead End' and a set of points were changed. The gradients on the hill were steep and C.C. Singleton of the Australian Railway Historical Society records the memory of a train driver descending the hill, 'wooden brake blocks ablaze and the engine in back gear'. In March 1886 a train lost control on the descent and 15 were injured. The buffer system and Zig Zag junction points were altered in an attempt to prevent a reoccurrence. The Railway Guide of New South Wales, 1879 described the journey toward the viaduct from Penrith, and then the structure itself, rather more romantically, 'the Railway may be seen winding upwards - past huge rocks and steep declivities, alternating with dense woods; the noble viaduct across Knapsack Gully being hence already distinguishable . . . You have by this time arrived at the Knapsack Gully Viaduct - boldly erected across a steep and stony gorge by the genius of the Engineer in Chief, John Whitton. This admirable and imposing structure (which Imperial Rome . . . might have been proud to claim) consists of seven successive arches'. Nell Aston in 1988 imagined the view from the train as it crossed the Knapsack Viaduct before ascending the Zig Zag writing, 'it must have seemed like flying'. (Singleton, 1956, p. 124, Aston, 1988, p. 21, The Railway Guide of New South Wales, 1879, p. 34)

The completion of the rail line made trips to the mountains comparatively quick and easy for Sydneysiders, and many built 'weekenders' in the lower mountains which overlooked Sydney and enjoyed fresh mountain air. (Aston, 1988, p.11) The Blue Mountains area was generally opened up to development, and the rail line revolutionised transport of people, goods and supplies between Sydney and the agricultural areas developing to the west of the range, the railway reaching Bathurst in 1876.

The viaduct fell into disuse in 1913 on completion of the Glenbrook Gorge Deviation, to the south of the zig-zag, which incorporated a similar viaduct and followed an easier gradient. In 1926, after over a decade of disuse, the Knapsack Viaduct was taken over by the Main Roads Board. The Board sought to improve on the steep gradients of the Great Western Highway between Emu Plains and Blaxland and found that a suitable line was presented by part of the old zig-zag railway formation, including the Knapsack Gully Bridge. The viaduct's carriageway was widened from the original sixteen to eighteen feet by trimming back the inside face of the stone parapets. The new road was opened by Governor Sir Dudley de Chair on 23rd October 1926 (Blue Mountains City Library, photo file: PF 354/1 and P/F 354/3; Main Roads Journal, May 1939, pp. 92-4, Main Roads Board Annual Report, 1926, p. 21)

The viaduct was widened in 1939, with the construction of a reinforced concrete cantilevered deck, designed to be aesthetically sympathetic to the original structure, to accommodate increasing traffic volumes. The widening was undertaken by contractor Hardy Davis, Ltd. (RTA File 5/44.11221 Part 2, Main Roads Journal, Vol. 10, No. 1, November 1938) Further widening of the bridge was considered in the late 1970s, but the construction of a sympathetic parallel structure at some distance from the bridge was considered greatly preferable (RTA File 5/44.11221 Part 2)

The deviation of the Great Western Highway (M4 Motorway) around the gully relieved the structure of the burden of traffic in June 1993. Penrith Council, the Roads and Traffic Authority and the Federal Government collaborated to adapt the area for tourist access to the Viaduct so that it might be viewed and appreciated by the public. In 1995 the bridge was reopened along with the John Whitton Memorial Reserve, by Member for Macquarie, Maggie Deahm (Penrith Press, 12th December, 1995).

Historic themes

Australian theme (abbrev)New South Wales themeLocal theme
3. Economy-Developing local, regional and national economies Transport-Activities associated with the moving of people and goods from one place to another, and systems for the provision of such movements (none)-

Assessment of significance

SHR Criteria a)
[Historical significance]
The Knapsack Viaduct is of historic significance, having formed a vital component in the rail line over the Blue Mountains constructed in the 1860-70s. The construction of the Lapstone ascent and this monumental and labour intensive viaduct, was a significant event, altering the Blue Mountains landscape permanently and shaping the history of nearby local communities over several decades. The story of the bridge - its life as a rail bridge for three decades, subsequent disuse for over a decade, reuse as a road bridge from the late 1920s, and its more recent adaptation for tourist access, has shaped the form of the bridge itself and makes it a highly articulate structure in the wider story of rail and road transport over the mountains, which has shaped the history of the wider Sydney area and its relationship with the State's west.
SHR Criteria b)
[Associative significance]
The Knapsack Viaduct has a strong association with John Whitton, second Engineer-in-Chief for Railways, who designed and supervised the construction of the bridge itself and the ascent of the Lapstone Hill of which it is a part. The route of the rail line, the viaducts and Zig Zag ascent and descent of the range reflect his solution both to the formidable terrain of the range and the funding limitations imposed on the project. Although Whitton was responsible for many significant rail projects across the State, the Knapsack Viaduct is widely regarded amongst railway enthusiasts and the wider community as having the capacity to express Whitton's genius, his masterpiece.
SHR Criteria c)
[Aesthetic significance]
The Knapsack Viaduct has a high degree of aesthetic significance, being a commanding and beautiful structure. It was a landmark on train and road journeys across the range for almost 130 years, and is now visited by sightseers and locals. The viaduct has inspired much photographic art and some painting. Its design and construction represent a creative and technical achievement, as the largest viaduct on the two Zig Zags that formed Whitton's innovative solution to a formidable engineering problem. It was reputed to be largest stone viaduct in New South Wales at the time of its construction.
SHR Criteria d)
[Social significance]
The structure is widely appreciated by the contemporary community for its cultural and aesthetic values. This high degree of esteem is evidenced in the concern of the local community regarding the future of the viaduct since its decommissioning as a road bridge, and in the high level of interest in the history of the bridge on the part of local writers and railway enthusiasts alike.
SHR Criteria e)
[Research potential]
The area adjacent to the bridge holds much evidence of prior usage by various rail alignments and roadways, including graded inclines and stone culverts. As a central element of these routes, the viaduct has potential, with other remnants, to yield information about the history and technical properties of lines of road and rail negotiating the Lapstone Hill.
SHR Criteria f)
The Knapsack Viaduct has rarity value as a stone arched viaduct. It is one of a small number on this ex-rail route, and a small number surviving across the State, and unique for its size.
SHR Criteria g)
The viaduct has the capacity to demonstrate the key characteristics of the group of stone arch viaducts constructed for rail projects in Australia in nineteenth century, a limited number of which survive, and is also of rarity value for this reason.
Integrity/Intactness: High
Assessment criteria: Items are assessed against the PDF State Heritage Register (SHR) Criteria to determine the level of significance. Refer to the Listings below for the level of statutory protection.

Recommended management:

Continued sympathetic management and increased emphasis on interpretation of the historic, technical and aesthetic properties of the structure to the public.


Heritage ListingListing TitleListing NumberGazette DateGazette NumberGazette Page
Heritage Act - s.170 NSW State agency heritage register     

Study details

TitleYearNumberAuthorInspected byGuidelines used
Study of Heritage Significance of a Group of RTA Controlled Bridges & Ferries2004 HAAH - Sue Rosen and Associates  Yes

References, internet links & images

TypeAuthorYearTitleInternet Links
Written 1995Penrith Press, 12th December, 1995
Written 1926Great Western Highway road deviation opening, 23 October 1926
Written 1926The Governor Sir Dudley De Chair opening the road deviation at Blaxland, 23 October 1926
WrittenAston, Nell, for the Glenbrook Public School Centenary Committee1988Rails, Roads and Ridges. History of Lapstone Hill- Glenbrook
WrittenBlue Mountains Historical Society Inc.2004Correspondence Joan Smith, Research Officer
WrittenDepartment of Main Roads1938Main Roads Journal, Vol. 10, No. 1, and No. 3
WrittenMain Roads Board1926Main Roads Board Annual Report, 30th June, 1926
WrittenP. Belbin & D Burke1981Full Steam Across the Mountains
WrittenPalmer, H. Some Bridges Around Penrith
WrittenPublished: Thomas Richards, Government Printer1879The Railway Guide of New South Wales
WrittenRoads and Traffic Authority RTA File 5/44.11221 Part 2
WrittenRowland, E.C.1954'The Story of the New South Wales Railways', Royal Australian Historical Society and Proceedings, Vol XL, Part V
WrittenSingleton, C.C.1956'Ascents of Lapstone Hill' Australian Railway Historical Society Bulletin No. 227 – September 1956

Note: internet links may be to web pages, documents or images.

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Data source

The information for this entry comes from the following source:
Name: State Government
Database number: 4301012

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