Chester Castle, Phase VI Conservation - Half Moon Tower & Frobisher's Workshops, for English Heritage, 2011

Stationed at the edge of Chester city centre like a sentry battling time, stands Chester Castle. The history and importance of this location is perhaps no longer noticed by the hundreds of shoppers, tourists and businessmen who pass by its gates every day, but this building has played a pivotal role in the history of our nation. Battles and wars have been won and lost on the surrounding pavements, roads and car parks. Men have fought and died here for Wales, for England, for Rome. The face of Chester has changed radically since then and continues to do so. The prosperous, civilised city that stands before us today is a far cry from the place in which the castle was built. One only has to look fifty yards across the road at the sparkling new glass and steel HQ hotel development to understand this change. Where our ancestors built colossal castles and curtain walls to keep people out, we answered history with gigantic architectural invitations to come on in.

The first castle, largely constructed of timber, was built on this site in 1069 by order of William the Conqueror, but it was on top of a Roman fort dating from 79AD overlooking a crossing point in the river Dee below. In the 1200s, a programme of building in stone began at the castle and the earliest of these buildings, the Agricola’s Tower, houses the chapel of St Mary de Castro where wall paintings from around 1220 were discovered during restoration work in the 1980s.  The rebuilding of the castle complex in stone was accelerated in 1237 by Henry III who commissioned several of the buildings we see standing today, including the Half Moon Tower and the giant masonry defensive walling, some 400m in length, both of which were included in the most recent phase of conservation work by Chester based historic building specialists Recclesia Ltd.

Also included in the conservation project was the rectangular building hitched onto the inner face of the Half Moon Tower, a building known as the Frobisher’s Workshops (from “Refurbisher”, where the repairs for the armoury were undertaken). Originally, this building was built for quite a different purpose. The 1690s bore witness to significant monetary problems in England thanks to years of war with France which resulted in the entire coin-based currency being melted down and reissued. In 1696 Edward Halley (of comet fame) established a mint at the castle in an effort to help refill the country’s purse. The mint did not last long, as the 1700s saw significant change at the castle as the Cheshire Regiment modified the fortifications for canon fire and added what was widely regarded as one of the most secure prisons in the land. The mint building, the only brick-built building still remaining on the site today, was turned into the armoury workshops and later on in its history it was changed again into the officers’ mess rooms when the square windows were punched through the outer walls of the adjoining Half Moon Tower by the Ministry of Defence.

The MOD left the Castle in the 1980s by which point the buildings were in a fairly muddled state. The military function of the buildings had taken precedent over the care of the building as a historical artefact and English Heritage were left with the task of trying to decipher the significance of each part of the castle complex. The inner courtyard had been filled with a variety of semi-permanent buildings, so the task of stripping these away to reveal some semblance of the original fabric cannot have been easy at all. Since the early 1990s, English Heritage has commissioned several phases of work to conserve and consolidate the original fabric. The latest of these was Phase VI, a £160,000+ contract wholly commissioned and financed by English Heritage’s in-house conservation funds. The project encompassed the Half Moon Tower and the Frobisher’s Workshop. Having been involved in several of the previous phases of work at the castle, it has to be said that this was one of the most complex to date.

The Half Moon Tower and the Frobisher’s Workshop are the only two buildings remaining that form part of the defensive walling of the castle itself. They are joined to each other quite crudely and built using completely different materials at very different points in time. The Half Moon Tower was built using inconsistent quality of stone and the weathering characteristics change by elevation. The Frobisher’s Workshop is brick-built and failing facing bricks were covered over in the last century with a hard cement based mortar, which only exacerbated the initial problems. Both buildings have suffered quite unapologetic modifications to their original layout and both had suffered the consequences of failing roofs. The objective of Phase VI works was to repair the external envelope of both buildings, along with internal structural work and timber repairs. The buildings are Grade I listed and Scheduled Ancient Monuments meaning that the work had to be of the highest standard and that the craftsmen and women involved in the project understood the conservation thinking behind the approach to even the most minor repair. As well as the safety briefings on site given by CPS Ltd of Shrewsbury, staff were given a history lesson explaining the background and importance of the castle buildings. Records were also extremely important and archaeologist Blair Poole of LV Archaeology in Chester was drafted in to undertake a detailed survey of the building from top to bottom.

A very carefully designed scaffolding was erected in September 2010, wrapping itself around the Half Moon Tower whilst standing on the steep slope of the outer bailey. The stripping of the slates and lead sheet roof areas was the first item programmed, revealing a fairly substantial problem with the roof timbers which were found to be in a much poorer state than originally anticipated. Worse was the fact that the three large trusses supporting the roofs above both buildings were found to be structurally unsound and rapid propping work was carried out to prevent their catastrophic failure. Lifting of the floors internally also revealed that the enormous eight metre spine beam which ran the length of the building from the medieval masonry of the defensive walls into the Frobisher’s Workshop was also quite seriously unsound. Further, many of the roof timbers – rafters, wall plates and purlins – were also in a bad way due to water ingress. All in all, the joiners were faced with a very difficult task of not only retaining as much of the original fabric as possible by splicing new to old, but doing it in a carefully planned sequence so as not to cause the wholesale collapse of the roof structure.

As the joinery repairs began up top, the task of carefully removing the cement render from the already delicate 1696 brickwork beneath began. This was a painstaking process taking many weeks, as the faces of the bricks simply fell to pieces as the render was drawn away – a well documented result of cement render being used to “solve” problems with brickwork. The condition of the bricks beneath was such that over four hundred individual bricks had to be replaced. Each irreparable brick was carefully cut out by hand and a new one slotted in until each elevation was sound enough to accept a new render coating. This time, the render was lime based and through-coloured on site using three coats of carefully gauged mixes of natural hydraulic lime and sands. Recclesia’s plasterwork specialist Matthew Bunn was responsible for tending to this element of the work, which was carried out whilst working around fairly cold conditions. This meant cocooning the scaffolding and wrapping up the freshly applied work without restricting air flow. His dedication to the task in tending to the render seven days a week, often until late into the night, meant that the frost was kept at bay and the render allowed to dry at the right rate.

Following lengthy discussions with English Heritage structural engineer Stuart Ellis, a design was produced for the insertion of three stainless steel supports to the roof trusses, which were fabricated off site and then expertly installed by Recclesia’s metalwork specialists Mike Batters and his apprentice Ben Austin. The three trusses were supported using large wheelbarrow type supports which transferred the forces exerted by the roof back onto the repaired wall plates above the thirteenth century masonry of the Half Moon Tower. It was a simple principle, but one which worked beautifully from the moment the propping below was removed. The spine beam was given additional support from beneath with the installation of a large steel stanchion.

As the timber repairs and structural works were completed, the roof began to go back on and work began on the conservation work to the masonry of the Half Moon Tower. The problems with the masonry were several-fold, exacerbated by the fact that stone of varying quality had been used in the original construction of the castle. It is possible that some of this may have been due to a possible rebuilding of the tower at some point in its distant past, but there is no documentary evidence to support this theory. Recclesia’s masonry conservation specialist Geoff Moore and architect Rob Green of Arrol and Snell Shrewsbury, carried out a detailed inspection of the masonry and a schedule of repairs required to each stone was drawn up. Recclesia stonemason Gordon Marsh was tasked with the intricate job of the delicate conservation work to the masonry which required extensive de-scaling, pinning, indenting, weather-shedding, and in some areas, replacement of ashlar back to its original plane. The masonry conservation exercise was followed by a general scheme of re-pointing using an hydraulic lime mortar.

As the works came together and the complex scaffolding was dropped from the outside elevation of the castle, the sad frowning face of the Half Moon Tower on show before works was finally chased away revealing a building which looked much prouder to be still standing. As the works to the inner elevations drew to a close and the rendered elevations of the Frobisher’s Workshops were unwrapped from their winter cocoon, a strikingly charming building emerged into the spring sunshine. With the building having been so thoroughly covered up for so long, even the team who had been working at the site day in day out were astonished by the immediate transformation that took place during the final few days of the project. Further, the entire complex of buildings inside the castle walls seemed to be lifted at the same time, making more sense of the historic site as a whole.

Today, the castle stands in a state of quiet limbo, but embryonic plans are being considered to find a new use for part of the site and it is with well placed and genuine optimism that we as a Chester based company and as Cestrians, wish this process well. In a city as rich as Chester is in historically significant assets and attractions the value of the castle in this respect is perhaps a little diluted, but it is nonetheless an extremely important tangible relic of English and Welsh military and social history. Like most historic structures the castle will require further conservation work in time, but this latest phase has been a decisive victory in the battle to protect the site as a proud reminder of the rich history Chester enjoys.