CASE STUDY: Chester City Walls

22 September 2011

Client - Cheshire West & Chester Council 
Design Team Architect - Giffords, Chester
Build Team Main Contractor - Maysand

Overview of the Project
Chester's Walls are the most complete circuit of walls in Britain, forming a remarkable 2-mile periphery around this historic city, so that Chester is quite rightly renowned as 'The Walled City.'  The Walls originate from Roman times, although they have experienced a rich history since including; Saxon and medieval rebuilding and extensions, Civil War conflict and Georgian elegance.
Maysand were appointed to restore a 30 metre section of the walkway which had collapsed on 3 April 2008 close to the Eastgate Clock.
The project meant re-using as much of the original masonry as possible, and every stone that was taken down had to be individually numbered and catalogued to ensure that it was put in its right position.
Maysand worked very closely with archaeologists, engineers and English Heritage to provide a bespoke restoration of the Roman Wall.  This included Maysand inspectors abseiling down many other parts of the wall to survey the extent of the damage.

The heritage project was a fascinating mix of engineering, archaeology and investigative work.

Innovation
The initial phase of the project called for specialist stabilisation work. This included installing props and anchors to support the internal face of the wall.  Maysand used 'CINTEC' who have developed an anchor system, which is installed entirely within the fabric of the structure, leaving no visible change to the outward appearance, a feature particularly liked by heritage authorities. CINTEC was previously used in both Windsor Castle and restoration work to Buckingham Palace.

The 'CINTEC' system comprises a steel section in a mesh fabric sleeve, into which a specially developed cementitious grout is injected under pressure. The flexible sleeve of woven polyester restrains the flow and expands to about twice its normal diameter, moulding itself into the shape and spaces within the walls, providing a mechanical as well as chemical bond.  The large surface area of the anchor, in conjunction with the pressurised grout, creates an anchor system that dispenses with the need for unsightly patress plates on the exterior of the structure, creating an invisible mend.

Integration
Maysand worked hand in hand with a number of bodies to ensure a successful project, including English Heritage, Giffords, Chester Renaissance and the council archaeologist. The latter was based on the site throughout the project.

The nature of the project was such that the inconvenience to the public caused by the work on a major tourist attraction had to be balanced with the importance of the site to the nation's heritage.

It had to be a team effort and much of the on site strategy fell into place with a series of pre-planning meetings, where roles, objectives and processes were clearly defined. That led to a very harmonious site.

Knowledge Management
Before work on site commenced there was a great deal of pre-planning and then, throughout the process, there was lots of recording being done which helped enormously. The big lesson: the more you have recorded up front the smoother the project.

The other big lesson was around communication. On such a nationally important monument, which is a major tourist draw it was important that the public were kept informed about what was happening, timescales and the nature of the work itself.

In addition to regular PR and signage, a web cam was installed that offered real time images of the work in progress. This of course meant that site operatives had to have an awareness throughout that there every move could be seen by the public. Toolkit talks were given about the detailed nature of the work.