Case Study: Monnow Bridge, Monmouth, Wales

The Monnow Bridge is the only remaining fortified river bridge in Great Britain with its gate tower standing on the bridge. The historical and architectural importance of the bridge and its rarity are reflected in its status as a Scheduled Monument and a Grade I listed building.

Patently unsuited for modern traffic and after repairs had to be undertaken in 1982 following a collision on 18 May in which a doubledecker bus struck the bridge, resulting in its closure for a month. Damage to the bridge and gate through accidents continued, and in the early 1990s, two drivers were prosecuted after crossing
the bridge with vehicles significantly exceeding the weight and height limits.

Given the importance and age of the structure and the nature of the construction, the materials used in construction and it’s location, Cintec International were invited by Monmouth County Council in 2012 to put forward a structural solution to stabilize the Gatehouse in such a way as to effectively and inconspicuously secure the future of the building.

Capita Symonds had issued a report in 2011 proposing structural repairs in general terms which after inspection were considered necessary by the client.

Cintec along with the County Engineer jointly surveyed and assessed the scope of structural repairs to the Gatehouse.

A scheme was devised and agreed with the client which was then the subject of an Ancient Monument consent application. This was granted without any amendments
being necessary and the work subsequently carried out in 2012.

The overall general condition of the masonry was reasonable apart from deteriorating pointing but there were some major areas of concern where cracks in the wall had developed indicating movement of parts of the structure and separation of individual elements.

Areas of concern were inspected and specific repairs for individual items identified were specified to ensure the long term stability of the structure for generations to come. All anchors were installed using diamond core drilling techniques with the anchors set within the walls with concealed entry points.