Avon Crescent Substation

Summary

Electricity substation, 1905-1906, by L G Mouchel of the Hennebique Concrete Company.

Reasons for Designation

The Avon Crescent Substation, 1905-1906, is listed at Grade II, for the following principal reasons:

Architectural interest:

* as one of the earliest examples in England of the technologically-innovative and highly influential Hennebique system of reinforced concrete construction; * applying a classical architectural treatment to a modern new material, using concrete to mimic architectural devices such as keystones and architraves, and adopting classicism’s associations of tradition and reliability; * retaining features from an extravagant scheme of internal fittings, intended to be visible externally and appropriate to accommodate modern electrical equipment; * a rare example of the building type dating from an early period of municipal electricity supply.

Historic interest:

* along with several buildings in the Underfall Yard, providing evidence of the metamorphosis of power systems in the period 1884-1950.

Group value:

* with the Underfall Yard’s group of listed buildings and the hydraulic engine house particularly, which was equipped with electric pumps soon after the substation came into use; * with a wider group of listed buildings in and around the Floating Harbour which received power from the substation, such as the Bonded Warehouses and Ashton Swing Bridge.

History

The substation on Avon Crescent was commissioned to provide an electrical power supply to the City Docks in 1905. Power had previously been generated by the ageing steam boilers in the Hydraulic Engine House at the Underfall Yard (listed at Grade II*). These were the source of the power for an extensive hydraulic network extending across the length of the Floating Harbour, driving lock gates and swing bridges, as well as industrial processes within the corporation granary; the proposed addition of the Ashton Swing Bridge (listed at Grade II) to the hydraulic network would have pushed its capacity to the limit. A new rotary substation was proposed to the convert the AC power generated at the City’s Avonbank Power Station, Feeder Road, to a DC supply at 365 volts for the Docks. In addition to the hydraulic system, the substation provided power for cranes and hoists at the new GWR Goods Shed at Canon’s Marsh, the Bonded Tobacco Warehouses, and arc lamps in Clifton (all listed at Grade II). Plans for the substation were approved in 1905, and operation began in 1906.

The building is an early example of the Hennebique system of reinforced concrete construction. A letter from the City Electrical Engineer, H Faraday Proctor, to the City Engineer sought approval to use the new ferro-concrete system, and plans were drawn up by Louis Gustave Mouchel of the Hennebique Concrete Company. This innovative system brought the separate elements of post and beam into a single continuous structural framework. The building was equipped with three rotary converters, with provision for another three, and was opulently fitted out with decorative ironwork, oak joinery and tiling, while the exterior was given a classical treatment. The interior was lit from a glazed roof, and tall windows, now blocked, would have provided a view of the modern technology within. The original converters have been removed.

Details

Electricity substation, 1905-1906, by L G Mouchel of the Hennebique Concrete Company.

MATERIALS: a concrete building: a reinforced concrete internal framework on the Hennebique system, with shuttered concrete elevations. A corrugated roof covering has replaced the original patent glazing.

PLAN: the building has an irregular footprint of a right-angle triangle with a slightly concave hypotenuse, optimising its constrained plot between Avon Crescent and Cumberland Road.

EXTERIOR: the substation is a double-height building with a carefully-composed and fenestrated classical façade with ashlar scoring, with other elevations largely plain and blind, bearing the shutter marks of the construction. The principal elevation, facing north-east onto Cumberland Road and the Underfall Yard to the rear, is a symmetrical composition with five, double-height Renaissance-arched window openings, now blocked, with hood moulds, keystones and sills in concrete. To either side is a wide, slightly projecting bay with a flat-arched doorway; that to the right retains a roller shutter and is missing its keystone, and each has a blocked arched window above. There is a cornice and parapet. The elevation continues as a single storey to the left, and has an oeil de boeuf window, blocked, and a second such window on the corner elevation facing the road junction. The cornice continues along the curved south-west elevation. The building has a pitched roof above the machine hall, originally glazed, and flat roofs at the angles. A conical ventilator survives on the roof.

INTERIOR: it is understood that the main machine hall is a lofty space, originally lit from above by patent glazing, and by the large arched windows of the principal elevation. The machine hall floor is said to retain evidence of the six low platforms for the converters, with wrought iron grilles set above the cable and transformer subways. A concrete framework providing the horizontal members to support a manually operated gantry crane. Cantilevered concrete galleries, linked by a steel bridge, housed the switch gear; these are believed to retain some decorative wrought iron balustrades and oak handrails. Elsewhere, areas of the white and green tiling of the original scheme are understood to survive, as do some internal doors, and that the roof is supported on a series of steel trusses.

Sources

Books and journals
Lamb, Peter, Electricity in Bristol 1863-1948, (1981)
Lord, J, Southam, J, The Floating Harbour: a landscape history of Bristol City Docks, (1983), 99
'Electricity Supply in Bristol' in The Electrical Review, , Vol. 64, (19 February 1909), 305-309
Martyn, D, 'Industrial heritage recognised on the local List' in BIAS Journal, (2020, No 5), 55-57
Websites
Know Your Place Bristol: Historic Mapping and Monument records for Avon Crescent Substation, accessed 20/02/2023 from https://maps.bristol.gov.uk/kyp/?edition=
Other
Bristol City Council, Local List Review Report, 2019
Draft Conservation Management Plan: The Underfall Yard, Keystone, May 2013

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