Stone repairs were made to the building only when it was absolutely necessary. The authentic character of the building took precedence over all considerations except that of prolonging the life of the structure and materials. It was found that the predominant stone, limestone, may be cleaned with a soft brush and running water. This minimises damage to its white outer crust. There were many problems faced in cleaning the sandstone octagon on top of the main tower. A protective natural crust [of 2-3 cm] develops on sandstone after prolonged exposure to the air. This layer was accepted as the aged surface and no attempt was made to attain the colour of an original cut stone. Photo depicts the picturesque gothic bell tower under repair. (Photographer: Tony O'Connell).
A secondary micro layer of black deposits often forms on sandstone. This can be cleaned by using a powder developed for the cleaning of fine carvings within museum conservation. At St. Peter's, the octagon was dusted in a continuous layered manner to visually even the surface on which deposits had formed. Chemicals and harsh abrasives were avoided.
The repair and pointing of a building safeguards its longevity and structural efficiency. When repointing, mortar must be fully pressed into the joint, allowing no air gaps. Flush pointing was used throughout St. Peter's. Up to 150mm of mortar had to be pressed into the joints of the sandstone octagon. The stone was masked to prevent staining. Where necessary, old mortar was raked out to twice the depth of the width of a joint prior to reinstatement. Joints below 8mm were not raked out. Sands were sieved, cleaned and mixed to achieve a matching form to the original used.
Lime plaster allows a building to breathe. Lime is made by firing limestone which then releases carbon dioxide. In the plaster finish, the lime reabsorbs carbon dioxide and in time is turned back into limestone. It allows a small amount of moisture in but also allows trapped moisture to dry out. If a breathable plaster is not used externally in solid wall construction the results can be devastating as moisture is held within the wall. External walls were fully pointed in a sympathetic mix prior to plastering. In some areas more layers of plaster were used to match to stone architectural detail. All straight edges were finished by hand or with the aid of a timber guide. Photo depicts lime putty finish to the internal walls. (Photographer: Tony O'Connell).
The building was coloured with a traditional limewash to limit the contrast between the old and new plasterwork. The wash allows the building to breathe and has a life span of at least as much as an average modern paint. It is applied in thin layers and the final coat is oiled lightly with linseed oil. The wash is made from lime putty and water and has the rust colour of natural ferrous sulphate. Many earth pigments were used in the past, mainly in reds, yellows and browns. Three painters from different companies were trained and worked together on St. Peter's and then returned to their own companies with their new skills. Photo depicts the newly limewashed west elevation. (Photographer: Tony O'Connell).
Prior to the building of the tower, a stone belfry was used, which now sits behind the sandstone octagon. It is formed of two uprights and a pedimented lintel, doweled together. As it is in poor condition, it was decided not to replace its elements or to cut out any areas for repair, but to replace steel doweling with stainless steel versions and to repoint the stonework. It was finally coated with copper sheeting as a protective measure. It remains in its original position, protected for future reference. Photo depicts the disused belfry wrapped in copper. (Photographer: Tony O'Connell).