Historic Churches 2018

26 BCD SPECIAL REPORT ON HISTORIC CHURCHES 25 TH ANNUAL EDITION NEW OPENINGS AND OPPORTUNITIES Where new openings into the fabric of a listed building are required, these will need to be very carefully considered, fully justified and discussed in detail with the architect or surveyor. The works may well need formal approval from statutory bodies too. If the work is in a church or cathedral then it will be under the jurisdiction of the relevant body such as the Cathedrals Fabric Commission, diocesan advisory committee (DAC) or historic churches committee (HCC). Where normal listed building consent requirements apply then the conservation officer of the local planning authority should be consulted. Works in scheduled ancient monuments will of course require scheduled monument consent. Where any loss of historic fabric is inevitable, the investigative, opening up and reinstatement works should be taken as an opportunity to additionally survey, record and repair other services found. This can be an ideal opportunity to discover and record ancient artefacts or graffiti. During a recent project at St John’s College Cambridge, for example, a 300-year-old shoe was found in a wall after timber panelling had been removed to allow new emergency lighting cables to be installed. It is thought that the shoe was placed there to protect the Master of the College and its discovery provided valuable evidence of historic beliefs in ritual magic. After suitable records were made, the shoe was replaced in its original position along with a time capsule from the present day. BUILDERS’ WORKS The nature of historic buildings demands that all builders’ works must be carried out with far greater care than in general construction work. Specialist contractors are the key to a more satisfactory outcome. This often means that it takes longer to remove, replace or renew any building services installation in a historic building. Service routes may need to be longer or more convoluted to accommodate the structure. Where old services cannot be reused but retain a particular significance to the building, it is important to leave them in place. Equally, older or redundant services such as cables or pipework should not be removed if the removal is likely to cause further disruption to the historic fabric. This requires leaving them in an inert condition where services are disconnected, made safe or drained down and then recorded. Their removal should only be considered if they have no historic significance, the removal process is non-destructive, or if their retention might pose a future danger to the historic fabric, perhaps through rust or chemical deterioration. A practical example of the benefits of retaining older systems is the reuse of redundant gas pipes as electrical conduits (it was the early reuse of old gas pipework that gave rise to the idea of steel conduits for wiring in the first place). INSTALLING NEW CABLES AND RE-CONNECTING OLDER ONES Good practice dictates that, wherever possible, new continuous cables should be used throughout an installation to minimise the number of cable joints or in-line terminations. This dramatically reduces the risk of termination errors as well as the risk of fire from thermal cycling, the overheating and arcing of loose terminations. However, it may be necessary, for conservation reasons, to retain a buried cable or conduit if its wholesale removal and replacement would cause further unjustifiable damage to historic fabric. In this case it would be important to identify the location of re-termination points and ensure future accessibility. A comprehensive new lighting scheme at St Paul’s Cathedral was completed in 2007. As part of the initial investigative works, a significant number of existing heavy duty mineral insulated copper cables (MICCs) were tested. Installed in the late 1950s with an expected service life of 150 years, they were found to be in excellent condition and it was decided that they should be retained rather than replaced. Manufactured in the 1950s, the cable and its terminations were imperial rather than metric, so the main difficulty was in obtaining additional terminations for new joints. Eventually the contractors found a small stock holder and the modifications could take place with the older cables properly jointed to the new system. A similar problem often occurs where imperial conduits are retained and need to be connected to new systems. Generally, where older installed cables are to be retained and reconnected as part of a new installation, or where any other new junctions are required, all such terminations should only be made in fixed junction boxes with fixed-back terminals such as DIN rail or other appropriate connectors. The risks of thermal cycling for all cable types and terminations must be considered and all terminations should be made in easily accessible and suitable locations which should be identified and shown on new record drawings. Termination schedules for all intermediate junction boxes should also be included in the O&M manuals. CABLE TYPES AND CONTAINMENT Installations in historic buildings should be designed to have the longest service life that can reasonably be achieved, particularly where new openings in historic fabric are required, or where a scaffold is needed. For this reason, the use of any PVC or plastic cable containment is to be discouraged. For the majority of surface-fixed installations, MICC or ‘pyro’ cables should be used because they are more robust than almost all other normal cable types and are the most resistant to mechanical damage. The use of other proprietary ‘fire- resistant’ cabling for visible surface runs is not ideal because it is easily deformed by mechanical damage and does not normally dress as well as MICC around architectural mouldings and other details. However, fire-resistant cabling may be acceptable where it is not seen and is not at risk of mechanical damage. Steel wire armoured (SWA) cable, with its protective steel binding, is generally bulkier than MICC or proprietary fire-resistant cabling and is commonly used for power distribution (for example as a sub-main to a distribution board). Ideally, it should One of 38 bespoke electroliers designed by Light Perceptions for Lichfield Cathedral. The design is informed by the work of Sir George Gilbert Scott and Francis Skidmore in the cathedral's crossing screen and pulpit.