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Allanton Bridge
River Whiteadder, Allanton, Scottish Borders, UK
associated engineer
Robert Stevenson & Sons
date  4th August 1840 - 27th March 1842
era  Victorian  |  category  Bridge  |  reference  NT863546
An imposing two-span masonry bridge over Whiteadder Water at Allanton, designed by Robert Stevenson & Sons the family firm famous for its connection with Scottish lighthouses. The bridge remains in use and now carries the B6437 road.
Allanton Bridge crosses the Whiteadder just below its junction with Blackadder Water. Both waters eventually join the River Tweed. The bridge was built at the behest of Miss Boswell of the Blackadder estate, who was concerned that the road passing Allanton was often rendered impassable by flooding.
The bridge is 6.7m wide overall, with a 4.6m wide carriageway set between parapets 6.1m apart. The two segmental arches have equal spans of 22.9m with a low rise of 3.5m. The arch stones are 915mm deep at the springings and 760mm at the crown, with their joints radiating across the spandrels. The central bridge pier and the abutments are founded on sandstone bedrock.
The masonry is of broached ashlar, except for the pilasters, frieze, cornice, impost courses, and the base and coping of the parapet. The stone is generally soft red sandstone sourced locally, though stone for the springing courses is from Dalachy Quarry (NT209863) near Aberdour in Fife.
When the centring (formwork) for the arches was removed, once the mortar had set, it was reported that one arch settled by 60mm and the other by 67mm.
Allanton Bridge cost 6,058 to construct. It became Category B listed in June 1971.
It is likely that Robert Stevenson & Sons also designed the nearby Blackadder Bridge (NT864545). It was built in 1851 and has two elliptical arch spans of yellow sandstone.
Resident engineer: John Thomas Syme
Resident inspector: Mr Watson
Contractor: Mr Balfour, Balsillie
Research: ECPK
"Description of the Bridge over the river Whitadder, at Allanton (Berwick)" by John Thomas Syme, in Minutes of ICE Proceedings, Vol.3, pp.101-102, London, January 1844
reference sources   CEH SLB

Allanton Bridge