Back from the Brink
The belfry of St Andrew’s, Leighterton with cement-rendered
panels and rotting timberwork before restoration (below left)
and after (above)
St Andrews is a Grade II* listed church that stands in the village of Leighterton in the Diocese of Gloucester and the Parish of Boxwell with Leighterton. The church, built in the Cotswold vernacular tradition, has been a central feature of village community life for generations, with the building’s nave, south porch and tower dating back to the 13th century.
A substantial range of additions and restoration works was carried out to this charming medieval church in 1877, including the removal of the upper part of the tower and the construction of a timber-framed belfry with a steep, timber shingle spire roof. But, after more than 130 years’ service, a close inspection of the belfry proved it to be in a state of disrepair and suffering wet rot. The challenge was to restore the structure and ensure the stability and structural integrity of its 19th-century timber frame.
From the outset of the project there was a strong commitment to retaining as much of the original structure as possible and replacing only those timber members which were defective and affecting the integrity of the structure. The plan was to remove all previous inappropriate repairs and materials and to repair the structure using original methods, such as pegged timber joints and lime render infill panels, and to reinstate the original paint finish on the timber frame.
Key to this restoration work was the design of a method to jack up the whole roof structure high enough to allow the angling-in of new posts and sole plates.
The belfry consists of a structural timber frame with a decorative arrangement of braces, constructed mainly of softwood with oak sole plates. The tower is square in plan with the members in all four sides of the timber frame arranged in the same way. In the centre of each side is a full height panel of louvres constructed with oak shingles. The timber frame is in-filled with render panels.
The belfry was identified as being a particular matter for concern during the quinquennial inspection of the church in 2007, which was the first inspection of St Andrews undertaken by the author. It was apparent that the frame had been repaired several times in the recent past and an oak ‘skirting’ board had been added to the outer face of the sole plates on the south and west sides. Some of the repairs had involved the use of ferrous bolts and nail fixings, which were showing signs of considerable rusting and deterioration. In addition, some of the timber members, mainly posts, had areas that had been cut back and re-faced. These repairs had seemingly been carried out to deal with the advancing effects of wet rot in the timbers.
The inspection of the belfry timbers was limited because it was not possible to get sufficiently close to them externally. Access was available up the tower internally, but here the timbers of the frame appeared to be acceptably sound and dry. From the inside it was also possible to observe that most of the original render panels had been replaced in the recent past. The few surviving original panels were formed with riven oak laths, but the replacement panels had been formed by the removal of the original oak laths and replaced with galvanised expanded metal lathing on softwood battens backed with reinforced bituminous roofing felt and finished externally with a hard cement-based render. One of these replacement panels had fallen out and was found lying on ground. When inspected it was clear that the expanded metal lathing had rusted and failed.
In March 2008, Verity and Beverley was provided with the opportunity to inspect the belfry timbers from the outside using a cherrypicker. The parochial church council (PCC) had arranged for the hire of the machine to clear gutters by Forrester Access under a scheme promoted by the Diocese of Gloucester called GutterClear. This inspection indicated that wet rot in the lower sections of the frame on the south and west sides was fairly well advanced and that this had clearly been accelerated by the use of cement render for the panels. It could be seen that the render panels had shrunk away from the timber frames, allowing an easy passage for the entry and trapping of water in the resulting voids. The use of cement render was preventing the drying out that would have been achieved with the original lime-based render. With the prevailing wind from the southwest, the south and west sides of the frame were those most affected.
|Separation between the frame and the cement-rendered panels provided an easy route
for driving rain to enter the structure causing timber to decay and the metal lath to rust
|The belfry jacked up to allow new and repaired timbers to be swung in|
ASSEMBLING THE RESTORATION TEAM
In May 2008, Carpenter Oak & Woodland, a locally based specialist in the repair and restoration of historic timber structures, was consulted regarding repair methods. Structural engineer James Birdwood of BTA Design in Shipton Moyne, Gloucestershire, was appointed as part of the restoration team. Verity and Beverley was to act as CDM co-ordinator for the project, in addition to being the project architects. An analysis of the quotations received had indicated that it would be most cost-effective for a conservation contractor to carry out all the repairs and works. However, being a small parish, the PCC did not have sufficient available funds to be able to commit to a contract and the team was instructed to do nothing further until funding could be secured.
By July 2009 the PCC had obtained a faculty approval from the Diocese of Gloucester to carry out the works using the information provided by the restoration team. With help from the diocese in obtaining supporting grants and funding, the PCC was in a position, in December 2009, to instruct the team to proceed with the project. The selected contractor, Ward & Co (Building Conservation) Ltd, was appointed and the team waited until early spring to start work to avoid the possible effects of bad weather and frost, with works arranged to commence on 6 April 2010 and complete on 25 June 2010.
ON SITE AND JACKING UP THE TIMBERS
|A new frame member being finished on site by Peter Mellish of Ward & Co to match the original profile|
Following the erection of the scaffolding during the first week of the contract, the render infill panels were dismantled and the boards that had been applied to the face of the sole plates were removed. This gave the team full access to the exterior of the belfry, enabling a more detailed inspection of the timber frame.
A method was devised for the insertion of the new frame members which entailed releasing four original holding-down bolts, one in each corner, and jacking up the whole roof structure with jack props off the top of the inner masonry sill of the tower. To minimise the possibility of any damage to the roof structure and its stability, the roof would be raised only enough to be able to allow the ‘angling’ in of new posts and sole plates. The contractors proceeded with opening up and removing the rotted sections of the timber frame.
During earlier inspections, remnants of an original brown paint finish to the frame had been discovered under the protection of the eaves of the tower roof. It was felt that this should be reinstated as it was the original intention of the architects to finish the timber frame with paint. In addition to providing a weatherproof finish, this would also unify the patchwork of repairs that would result from the works.
Analysis of the paint indicated that it was a standard lead-based oil paint typical of the 1880s but it was decided that, for health and safety reasons, a lead-based paint would not be used. Instead, a water-based paint with a similar appearance and durability was specified. This was particularly important in consideration of its suitability for future maintenance. Although the original paint material was not exactly replicated it was felt that the reinstatement of a paint finish to the timber frame was still compatible with the spirit and philosophy of the restoration.
Works proceeded with the formation of the new frame members, all of which were formed on site by skilled craftsmen. The frame joints were required to exactly match the originals where they were being replaced, and were fixed together in the traditional manner with tapered timber pegs. It was agreed with the structural engineer that the additional use of angled stainless steel dowel pins would be prudent at the junction of the corner post and sole plate in one location due to the condition of the original timbers.
From a study of the surviving timber lathing it was clear how the original infill panel had been constructed. Grooves in the original timbers had provided a weathering key for the render panels, and these were exactly replicated in the new timbers. New riven oak laths were fixed to match the existing, and the infill panels were finished externally with a smooth lime render flush with the face of the timber frame, and internally with lime render torching to the back of the laths.
PROJECT COST AND COMPLETION
|Finished belfry with shingle louvres, lime-rendered panels and newly painted timbers|
The contract account had been closely managed throughout with the adjustments costs for all variations being reported to the client. The works were valued at four-weekly intervals and interim certificates issued to the client for progress payments to the contractor. By closely working with the contractor to agree variations to details of repair, and by the careful management of the costs, the project was completed for a little below the contract sum.
Following completion there was a three-month defects liability period at the end of which the completed work was inspected. There were no significant defects to attend to but instructions were given to return to site to check and finally tighten the four corner holding-down bolts.
Restoring St Andrews’ belfry has been a hugely engaging experience involving some very specific technical challenges, particularly jacking up the roof. By thoroughly inspecting and understanding the problems suffered by the structure, and carefully considering the methods of its original craftsmen, the restoration team has ensured the structural integrity of the belfry. This in turn ensures the continued life and use of a historic building that is a central focus, both visually and socially, within the village of Leighterton, and of cultural importance to us all.