Architectural Joinery

The Challenge of St Vincent Street

Sarah Gerrish


	The pulpit platform, stair and ‘aedicule’ framed doorway (Photo: George Crawford/www.croftglenimages.co.uk)

St Vincent Street Church, Glasgow was designed by the great Scottish architect Alexander ‘Greek’ Thomson. Completed in 1859, it is believed to be his only intact surviving church and it remains in ecclesiastical use today. In 1997 the category A listed church was transferred to the Alexander ‘Greek’ Thomson Trust and was put on the World Monuments Fund’s watch list of 100 most endangered sites.

Glasgow City Council initiated a programme of repairs to the church and Page & Park Architects was invited to prepare proposals and a specification for the works, which included essential repairs to the roof. Conservation works to the tower were completed as phase one in 2000, with phase two of the conservation work, dealing with the main and side aisle roofs, also now complete.

In 2007 Sarah Gerrish Conservation was approached by Page & Park Architects to act as a consultant advising on the treatment of the historic wooden interior of this unique church. To facilitate the roof works, which required the structural reinforcement of the three roof trusses, an internal scaffold was needed to provide access to the perimeter of the three main timber roof trusses and to provide temporary support for each of the trusses while repairs were carried out to the truss ends. The main contractor gave careful consideration to the design, installation and type of scaffolding to be used in this process. Practical constraints were balanced with the need to preserve the interior as far as possible.

To allow the scaffold to be constructed, some of the pews and floorboards on the ground floor and gallery level had to be removed to allow the scaffolding poles to pass through to the undercroft below. It was necessary to remove the undercroft ceiling and take up the undercroft floor to allow the scaffolding poles to be sunk into the ground beneath.

Although the church’s original woodwork looked robust, it was highly vulnerable and care was taken at every stage of the conservation process to ensure progress was maintained at a slow and steady pace.

THE CONSERVATION APPROACH

The approach at St Vincent’s emphasised conservation rather than restoration. The aim was to preserve and stabilise as much of the original wood as possible using treatments that are technically reversible. This means using only materials that have been thoroughly researched and tested so that their behaviours in different environments can be predicted. Furthermore, it should always be possible to remove or ‘reverse’ a treatment at some point in the future without causing undue damage to the original artefact, if a better conservation method or a more appropriate material is discovered.


	The interior seen from gallery level (Photo: Phil Sayer, licensor www.rcahms.gov.uk)

Documentation is another key aspect of the conservation approach, including condition surveys, treatment reports and photographic documentation showing the artefact before, during and after treatment. These records also enable conservators working on the artefacts in the future to establish how best to proceed.

While the principles of conservation governed all aspects of the work at St Vincent’s, the complex nature of the roof works dictated a more invasive approach to the architectural joinery of the interior than would ideally be chosen. The timber conservation proposals (outlining what was to be done) and method statements (outlining how it was to be done) ensured a minimally interventive approach for the long term protection of this historically important interior and its furnishings.

AGENTS OF DETERIORATION

A crucial element of the conservator’s task is protecting fabric and artefacts from identified agents of deterioration. The agents affecting timber commonly include:

sunlight (UV radiation)
physical or mechanical damage caused during handling and cleaning, or by acts of vandalism, etc
biological decay caused by fungi (dry rot for example) and insects (woodworm for example) etc
environmental damage such as warping and splitting joinery, due to movement caused by high, low or fluctuating temperature, and changes in relative humidity
water damage caused by leaks, spillages, etc
fire or smoke damage.

There was no evidence of insect damage or rot in the pews and floorboards at St Vincent’s, although in many places the roof had been leaking for long periods of time. However, the patina and surface finish of the pews had suffered water damage in places from prolonged leaks in the ceiling.

THE PULPIT PLATFORM

In order to provide a method statement for the removal of the selected timber elements, it was necessary to understand how they had been constructed. The scaffold was designed to minimise disturbance to the existing architectural joinery. However, due to practical constraints, the timbers along the front line of the pulpit platform had to be removed. The platform has steps on either side leading up to the pulpit, and the bottom step was removed to allow five scaffold poles to pass through into the undercroft below.


	Internal scaffold in front of the organ and the pulpit

By crawling into the cavity under the platform it was possible to examine the construction and decide how best to remove the step. It was important to try to remove it without having to dismantle the whole structure. The carpet was carefully rolled back to reveal the steps, which were built on a wooden framework to which the treads and sides were nailed. Having marked the floorboard to be lifted it was possible to push the board up from the underside to ease it upwards. From the outside of the platform the nails securing the boards to the frame were cut along the front edge where the step met the riser using a very fine toothed saw and taking care not to mark the wood.

From underneath the platform, wedges were hammered in to lift the boards and the floorboard was prised from above at the same time using blocks, taking care not to bruise the front of the boards. Working systematically from above and below in this way along the length of the board ensured even lifting and prevented the board from splitting. At the mitres, the pins holding the boards down were punched through using a nail punch, which enabled the board to be gently prised up from the upper surface and wedged from underneath for an even lift.

Once the board had been removed, the framework of joists under the platform was exposed. It became clear that one element of the joist lay in the path of one of the scaffold poles. It was not possible to remove the joist to allow the scaffold poles a free path without dismantling the whole framework and platform above, which was considered too invasive and not feasible. The organ had also been built into the platform, so this structure, built in 1904, would have had to be removed too. The solution, although not ideal, was to cut a notch out of the joist and to retain the piece to re-fit after the works were completed.

The floorboards running under the platform and pulpit appeared to have no joints in them where the boards to be removed were located. The platform was built over the floorboards, which should ideally be lifted at a natural joint. However, this too would have involved dismantling the platform so it was necessary, using a very fine toothed Japanese saw, to cut a section of floorboard to enable the scaffold pole to pass through, the pieces were retained to be replaced after removal of the scaffolding. The floorboards in this area are not usually seen as they are located under the platform.

THE GALLERY


	Gallery fascia with cast-iron column capital (Photo: George Crawford/www.croftglenimages.co.uk)

The scaffold poles also had to pass through the gallery, which involved removing one row of pews and the floor so that a core drill could be used to pierce the floor of the gallery and the plasterwork ceiling, allowing access for the scaffold poles. Initially, it was thought that pew number 127 would have to be removed from the gallery along with the floorboard beneath it. The pews were jointed into the floor so it was necessary to remove the floorboards before the pews. The pews were built into a wooden framework that runs under floor level. They are an integral part of the construction of the tiered gallery and the floor and so it would have been a major operation to remove the pew without interfering with other structures. Ultimately, after very careful measurement and consultation of the scaffold plans, it proved possible to remove the floorboards and construct the scaffold without removing pew 127.

The implications were double-edged: unnecessary dismantling of the pews was prevented but the scaffolders would have to be very accurate when locating the required five poles as they would only have the smallest possible hole through which to insert the long poles.

It was suggested that a jig should be used to help with the pole location because if the poles were to slip, damage would be caused to the wooden structures and plasterwork. The floorboard consisted of one long run so the five poles were located in that area to prevent the need to lift any further floorboards on the curved sections of the pews. The pew’s book-rest was very near the area where the poles penetrated so it was necessary to protect the book-rest and back of the pew while the scaffold was erected using plywood sheets and bubble wrap.

THE PEWS

Five pews in the main body of the church had to be removed to allow the scaffold to be erected. From surveying the existing pews it was determined that every second leg support of the pews was nail fixed through the flooring to the joist below. Using hardwood wedges each leg support was carefully released. The centre joint of the pews was butt jointed with timber dowels. Using the same method with wedges, one side of the pew was released and then, by moving the pew sideways, the dowelled joint was freed. The left hand section of the pews, facing the front of the church, also had a central mortise and tenon joint. Once the pew was free from its leg fixing, the mortise and tenon joint could be freed.

ENVIRONMENTAL CONDITIONS

Once removed, the pews were carefully packed in bubble wrap and stored at the back of the church. It was decided not to remove them for several reasons, principally because placing them in storage would have meant exposing them to a different set of environmental conditions that could have adversely affected them. The ideal conditions for the woodwork would be a temperature of 18-20°C and relative humidity of 50-55 per cent plus or minus 5 per cent. While the church itself does not present ideal environmental conditions (it is quite cold and damp during the winter months) it is the fluctuation of temperature and relative humidity that is especially damaging, potentially causing wood to shrink, split or warp. Transporting the pews, which are over 20 feet long, would also have been both awkward and unnecessary. The more artefacts are handled the more likely it is that they will incur damage.

REPLACING THE HISTORIC TIMBERWORK

All fixings were retained during the removal of the pews and floorboards and, wherever possible, these were re-used in the original fixing holes to avoid drilling into original timber unnecessarily. The brass umbrella stands and holders attached to the pew ends were removed and labelled before they were dismantled and the screws retained to ensure that they were replaced on the correct pew and using the original fixings on completion.

All the elements that were removed to enable the scaffold to be built were carefully labelled and wrapped and care was taken to replace them in the correct aspect on their return.


	Thomson's elegantly curved pews (Photo: George Crawford/ www.croftglenimages. co.uk)

Every effort was made to protect the pews, pulpit/organ ensemble and other wooden elements that remained in situ throughout the works by encasing them in free-standing plywood boxing and plastic sheeting to protect from building dust and mechanical damage. Nevertheless, it was inevitable that the woodwork became very dusty. Proposals were drawn up for cleaning the woodwork that involved vacuum cleaning all excess dirt and dust, a controlled wet clean, tinting in areas which had been water damaged, and protecting the woodwork with wax polish. The protective boarding covering the pews and scaffold planks were all vacuumed before disassembly to prevent building dust falling onto the historic woodwork as per the recommendations. The main contractor undertook the responsibility for the basic cleaning of the wooden elements after the scaffold was removed.

CHALLENGES AND REWARDS

Typically, the conservation of historic interiors is carried out in a complex and sensitive environment. The conservator has to work around the tight limitations imposed by the need to minimise the risk of harm to a large and diverse range of historic artefacts and fabric. Intervening to conserve one element of a historic interior, like the woodwork at St Vincent Street, often threatens to impact on a host of others, all equally deserving of respect. Conserving sensitively and responsibly under these conditions can be enormously challenging, but the rewards for all concerned are every bit as great.

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Author

SARAH GERRISH ACR is an accredited conservator and has been practising for 20 years. She has worked for the National Museums and Galleries of Wales and National Museums Scotland as a furniture and wooden artefacts conservator and now runs her own business, Sarah Gerrish Conservation, from her workshop in Edinburgh.

Email
sarahgerrishconservation
@hotmail.co.uk.