Conservation work to take place on City Walls in Chester

This month Northgate Bridge will see two of its parapet stones replaced as part of a conservation project on Chester’s historic City Walls.

The steps onto the City Walls at this point will be closed for around four weeks from Sunday 11 August. However, the wall walkway and the Northgate Street footway will only be closed for a couple of days at each end of the project, while the scaffold is built and dismantled, and while the new stones are lifted into position.

The Council’s Bridges and Structures team has been monitoring the condition of one of the stones in the parapet on the approach to Northgate Bridge for a number of years, and the erosion has now reached a point where the stone is less than 100mm thick in places and is in need of replacement.

The next stone along is in slightly better condition but will be replaced at the same time because it is also deteriorating rapidly.

The Council’s Deputy Leader and Cabinet Member for Environment, Transport and Highways, Councillor Karen Shore said: “The sandstone used in the construction of Chester’s City Walls was laid down in layers over thousands of years, and ideally, in the construction of a wall, stones would be cut and laid in such a way that the layers are stacked on top of each other.

“Sometimes though, where taller stones were needed, stones had to be laid sideways on, so the layers are prone to peeling away over time, rather like the layers of an onion. That is what has happened on the approach to the Northgate Bridge.

“The City Walls are a legally protected Scheduled Monument, which means that all the work we do must be granted consent by Historic England. The Council has negotiated an agreement with Historic England that allows us to carry out carefully defined minor routine maintenance work without the need for consent each time.”

The amount of stone to be replaced for this project is quite large compared to normal minor work, so engineers have worked with the Council’s Conservation Officers to confirm that it falls within the limits of the agreement.

The Conservation Team has also approved the source of the new stone to make sure it matches, as closely as possible, the properties of the original.

Stonemasons working on the project have used laser scanning technology to carefully map the shape of the parapet, and of each of the stones, which are curved to follow the curve of the wall below.

They have used the scans to create drawings and a template to guide the cutting of the new stones so that they should fit into place perfectly. Time on site, and therefore cost and disruption, is minimised by cutting and shaping the stones as much as possible beforehand.

While the scaffold access is in place, stonemasons will take the opportunity to check the security of the other parapet stones, remove any loose material and repoint the wall next to the steps.

The schedule for the work is for the scaffold to be built and the old stone will be carefully chipped away. The new stone will then be lifted in the following week.

The most disruptive work will be done on each Monday when a neighbouring restaurant is closed to avoid affecting their business.