page_title: Barmouth Bridge
section_title: Background and construction
hierarchical_section_title: Barmouth Bridge / History / Background and construction
context_page_description: Barmouth Bridge, or Barmouth Viaduct is a Grade II* listed single-track wooden railway viaduct across the estuary of the River Mawddach near Barmouth, Wales. It is 699 metres long and carries the Cambrian Line. It is the longest timber viaduct in Wales and one of the oldest in regular use in Britain.
  Barmouth Bridge was designed by and constructed for the Aberystwith and Welsh Coast Railway on its line between Aberystwyth and Pwllheli. Work was authorised in 1861 and commenced in 1864. On 10 October 1867, the completed bridge was officially opened. Following the discovery of severe corrosion on underwater sections of ironwork, an intensive restoration programme was performed between December 1899 and late 1902. By 1980, the viaduct was under attack by marine woodworm, which led to concerns that it would have to be closed and demolished. Because of its value to tourism, it was repaired between 1985 and 1986 when it was closed for six months. Since 2005, weight restriction on the bridge have been relaxed, allowing locomotive-hauled trains to cross for the first time in two decades.
context_section_description: A bridge across the Mawddach Estuary at Barmouth was proposed by the Aberystwith and Welsh Coast Railway, who constructed a line between Aberystwyth and Pwllheli. Authorisation for the railway was received in 1861 - 2 and the detailed design of the bridge was started.
  Barmouth Bridge was designed by the civil engineers Benjamin Piercy and Henry Conybeare. Conybeare wanted a timber viaduct because it was about four times cheaper to import wood from the Baltic by sea than to construct an iron bridge. The decision was influenced by the incorrect belief that the estuary was free from marine borers, which attack and weaken the timber over time. During this era, timber pile viaducts were commonplace on coastal railways, particularly in Wales, although the bridge at Barmouth would be longer than most.
  Construction began in 1864. The contractor was Thomas Savin, and the ironwork was produced by John Cochrane & Sons. Early on, progress was hindered by strong tidal currents which caused multiple failed attempts to sink the bridge's piers from barges. Between March and June 1866, staging was built from the northern abutment for the bridge, and the piers were dropped into the water and filled with concrete.
  Wooden trestles were built on screw piles 10 inches (250 mm)-14 inches (360 mm) wide with screw discs 36 inches (910 mm) in diameter in groups of three piles per pier. Timber trellis girders, 40 feet (12 m) long and 4 feet (1.2 m) deep, supported the deck, with driven piles as fenders. The water around the trestles had a maximum depth of 54 feet (16 m) at spring tides but the river bed was raised by tipping stones to protect the piles.
  The viaduct had a 47 feet (14 m) wooden drawbridge near its northern end allowing tall ships to pass upstream. The drawbridge span, which was carried on top of wrought iron piles, opened by tilting and rolling back over the track on four 4 feet (1.2 m) wheels, spaced 50 feet (15 m) apart, and nine steel rollers. When opened, there was a 36 feet (11 m) gap between the fenders. The drawbridge never regularly used as the opening of the railway effectively eliminated the need for traditional boat traffic.
  On 3 June 1867, horse-drawn carriages crossed the viaduct. On 10 October, the bridge was officially opened, and steam-hauled services started.
caption: A steam-hauled train traversing Barmouth Bridge, circa 1921
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