York City Walls are also often referred to as the Bar Walls or the Roman Walls, although very little of the extant stonework is of Roman origin, with many sections having been substantially altered since Roman times. However, the walls remain the most complete example of medieval city walls still standing in England today, and there are some remains of earlier walls below, dating as far back as the Roman period.
With such a historic pedigree, both construction and age-related wear and tear is inevitable, with some significant voiding discovered beneath one of the sets of steps leading up to the rampart at the Monk Bar gatehouse entrance to the walls. This voiding beneath the steps had begun to impact on their stability, causing the steps to loosen with the potential for them to collapse. Not only would this have been dangerous from a health and safety perspective but would also have impacted on the historic appearance of this much visited tourist attraction.
York City Council, who manage the walls, required a permanent solution that would effectively fill the void beneath the steps, both stabilising and supporting them, yet any such solution had to have its methodology and materials passed by the Historic Buildings Council to ensure they would have no deleterious effect on the steps or wall.
In addition, as a busy tourist attraction, as well as being highly trafficked, any solution had to be quick and efficient and minimally disruptive.
The historic sensitivity of the site limited the available options, as well as the need to keep disruption to a minimum. Traditional fill material could not be used to fill the void as it posed a number of problems, one being its potential to pressurise the containing vertical wall and therefore there was a need for a lightweight material inside the void to support the steps without putting any pressure on the structure.
Any proposed solution also had to go through a process of evaluation and approval by the Historic Buildings Council, in order to be passed as acceptable and not deleterious to the existing stonework or structure as well as being a permanent solution.
Geobear, was chosen as the solution it presented met all the criteria required to permanently fill the void and provide the necessary support for the steps. The Geobear solution was also fast to install, which would limit the time the steps and wall section would be out of use to the absolute minimum.
Our geopolymer was accepted by the Historic Buildings Council, meeting its strict criteria of preserving the steps and walls appearance and integrity, whilst providing a permanent solution to the voiding issue.
We worked alongside a team of stonemasons, who had been appointed by York City Council, to address the physical aspects of the step’s repair, the stonemasons provided their expert input into Geobear’s solution as required.
The works only required us to be on-site for half a day, injecting geopolymer resin – a lightweight bulk void filler – into the void below the steps, filling it to provide the required support the steps and a permanent long-term solution.
Geobear successfully completed the project, on-time and to budget and fully to the demanding criteria of the Historic Buildings Council and York City Council.