Underfall Yard
The Underfall Yard is a historic boatyard on Spike Island serving Bristol Harbour, the harbour in the city of Bristol, England. Underfall Yard was commonly referred to as "The Underfalls" and takes its name from the underfall sluices. The original construction was in the early 19th century with revisions by Isambard Kingdom Brunel in the 1830s. Following restoration in the 1990s, this Victorian work yard is now a Scheduled Monument that includes several listed buildings. The harbour and its equipment are still actively maintained, and host a cooperative of boat builders.

In the early nineteenth century, the engineer William Jessop was engaged by the Bristol Dock Company to create a non-tidal Floating Harbour to combat continuing problems with ships being grounded at low tide. With his system, which was completed in 1809, water was trapped behind lock gates so ships could remain floating at all times, unaffected by the state of the tide on the river. Part of the project included building a dam at the Underfall Yard with a weir to allow surplus river water to flow into the New Cut, an excavation that by-passed the Floating Harbour and joined the River Avon near Temple Meads. The docks' maintenance facility was established on the land exposed by the damming of the river to construct the harbour and remains sited at this location to the present day. By the 1830s the Floating Harbour was suffering from severe silting and Isambard Kingdom Brunel devised the underfall sluices as a solution. The Bristol Docks Company never achieved commercial success and was taken over by Bristol City Council in 1848. In 1880 the Council bought the Slipway and yard to enlarge the docks' maintenance facilities. The 'Underfall' system was re-built in the 1880s, with longer sluices, and the yard above was enlarged. Brunel's method of silt disposal is still in operation today, but the silt is carried in mud barges or pumped to the sluices through a quayside pipe system from the more efficient modern 'Cutter-Suction' dredgers. During the 20th century the western parts of the yard were leased to P & A Campbell Ltd, operators of the White Funnel Line of paddle steamers as a maintenance base. The yards have been little altered recently except for the replacement of the three-storey 'A' block over the sluice paddle room resulting from bomb damage in World War II. Underfall Yard has been refurbished under the management of the Underfall Restoration Trust thanks to Lottery money, European funding and financial support from Bristol City Council. Since the 1990s £500,000 has been spent on regenerating the slip and restoring buildings around the boatyard. Based at the yard at the moment are two wooden boat builders, a blacksmith, a ship rigger, a composites specialist (GRP, Carbonfibre), a narrow boat outfitter and a joiner.

Underfall sluices
Jessop's original designs for the harbour included a dam with an 'overfall', with the level of the water determined by the height of the dam's crest. As a result of the accumulation of mud and silt in the harbour, ships entering the narrow harbour were frequently being grounded. In 1832 Brunel was called upon to provide the solution to this problem and designed the sluice system, still in use today, to remove excesses of foul-smelling silt and mud. In place of the Overfall he constructed three shallow sluices and one deep scouring sluice, between the harbour and the New Cut, together with a dredging vessel, known as a drag boat, to scrape the silt away from the quay walls. Sluices 1 and 2 ('shallow') are used to control the water level, while sluices 3 and 4 ('deep') remove the silt. When the deep sluices are opened at low tide, a powerful undertow is created which sucks the silt out of the harbour and into the river. In March 1988, the sluice control was computerised and automated.

Most of the buildings and engineering installations at the yard were constructed between 1880 and 1890 under the direction of John Ward Girdlestone. Many of them have been designated by English Heritage as listed buildings. The original blacksmiths' and engineering workshops remain in use while the shipwrights' shop is now used as a carpentry workshop.

Hydraulic Engine House
The octagonal brick and terracotta chimney of the engine house dates from 1888, and is grade II* listed, as is the hydraulic engine house itself. It replaced the original pumping house which is now The Pump House public house. It is built of red brick with a slate roof and originally contained two steam engines. These were replaced in 1907 by the current electric machines from Fullerton, Hodgart and Barclay of Paisley. It powers the docks hydraulic system of cranes, bridges and locks. The tower houses an hydraulic accumulator which stores the hydraulic energy ensuring a smooth delivery of pressure and meaning that the pumps do not need to be running the whole time. The external accumulator was added about 1920. The water is pumped from the harbour into a header tank and then fed by gravity to the pumps. The working pressure is 750 lbf/in² (5.2 MPa).

Dock maintenance workshops
The dock maintenance workshops are also survivors from the 1880s but were extended in the early 20th century. The brick building is topped with a tiled double-pile hipped roof with corbelled eaves. It has sliding doors at each end, giving access to the boiler and engine houses, blacksmith's and engineer's shops. Much of the original machinery survives, including steam-powered plant from the mid 1880s, these include a Whitworth planing machine, a Whitworth slotting machine, punching-and-shearing machines, a long-bed lathe and a steam hammer. There is also wall-mounted line-shafting and a Tangye horizontal engine and Cornish boiler.

Pattern maker's shop
The former pattern-maker's shop and stores date from the same period and are grade II listed, The shop is currently occupied by RB Boatbuilding Ltd, a small business dedicated to the re-creation of classic, late 19th century, wooden working boats, including the Bristol Channel Pilot Cutter. . The Slipway Co-operative Ltd manages the slipping of boats. They build, repair and restore a variety of wooden craft including the 14 feet (4 m) Bristol Jolly Boat.

The original slipway was built by John Ward Girdlestone in 1890 which had replaced a predecessor built in the 1850s by boatbuilders Ross and Sage. It used a system in which the ship is floated onto the cradle and secured. The cradle is then drawn out of the water with a steam-driven winch. The device was a low-cost alternative to dry docks for maintenance and repair work. This became known as the Patent Slipway or 'Heave-up Slip' and was patented in 1819 by shipbuilder Thomas Morton of Leith in Scotland. The 1890 replacement was originally driven by an hydraulic engine powered by the dock's hydraulic system. In 1924, an electric motor was installed which still operates today. The Bristol slipway is relatively small with a cradle of 100 feet (30 m) and a runway of 265 feet (81 m) and could lift vessels up to 250 tons (250 tonnes). It fell into disuse by 1974. By the 1990s this was becoming rotted and was rebuilt by members of the Slipway Co-operative and Underfall Trust in 1998-99. The restoration required the complete renewal of the underwater runway with steel piling to replace the previous timber, iron and masonry supports. The above-water track was re-laid, reusing the original cast iron centre rails with their integral ratchets. The cradle was completely rebuilt on the original pattern. The functioning of the slipway was essential for the long-term preservation of the restored Underfall Yard as a historic industrial monument, as it provided the Underfall Restoration Trust with funds to maintain slipway and buildings, and the tenants of those buildings with boats to earn a living.

Shipwright's shop
The shipwrights' shop dates from 1885 when it contained a mortar mill and circular saw powered by the engine in the machine shop. It is now used as a carpentry shop.

Waterside Forge
The Waterside Forge workshop can be found within Underfall Yard, alongside the slipway. The forge offers welding, fabricating and hull repairs. In addition, gates, railings, security grilles and ornamental iron work are also made from stainless steel, steel, aluminum and wrought iron.

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