SUPPORTINGCOLUMNS Questionsof stability StructuralengineerBrianMortondescribeshisapproachto the conservationof a redundant churchandsomealmshouses. A local authority had approached me with two problems. The first involved the possibility of issuing an emergency works notice on a redundant church where nothing had been done to maintain and protect the structure. The planner and conservation officer were both present at my inspection. Questions revolved around how much work needed to be done under an emergency works notice. The main issues were the condition of the flint work. Sections of the wall might need to be rebuilt, and holes in the peg tile roof were allowing water to penetrate. The flint wall had been re-faced by the Victorians when they inserted new windows. The problem was not a complete collapse of the wall but just the falling away of the outer skin of flint work in areas where water had been allowed to penetrate. The simple solution was to patch repair the structure of the outer face in these areas, perhaps using stainless steel anchors back into the main body of the wall. The question with regard to the roof was how far one can go with an emergency works notice. Initially I felt that we could perhaps agree to the partial stripping of some of the roof and then leaving it felted and battened. I subsequently decided that in a bad winter more tiles could blow off around existing hollow areas, resulting in the ruin of the internal plaster. The district council and the DAC were keen that no unnecessary works should be carried out which would be abortive if a purchaser was found. My recommendation was that the existing tiles over the whole area of roof should be stripped off and stored within the building, and that the roof should be felted and battened to the correct gauge to receive the tiles back again using a breathable felt. A further layer of untearable roofing felt, fixed down beneath counter battens, should be fixed on top of the battens to protect them. This would protect the permanent felt and battens for perhaps two or three years. I suggested that prior to issue of the notice, the proposed works were agreed with the DAC so that there were no delays in implementing them. The local authority had also asked me to look at a long, single-storey building built in 1908 as almshouses of soft red brick construction using a lime mortar putty. An engineer had inspected the building following the appearance of cracks in the cross walls, generally adjacent to the long external walls. The cracks were sometimes diagonal and sometimes were at the junction of the cross walls and the ceilings. There was generally little indicaCONTEXT 72 DECEMBER 2001 tion of cracks below eaves level on the inside face of the buildings. The engineers had thoroughly inspected the structure and come to the conclusion that vertical movement joints should be provided in the long external walls to divide the length of the wall into sections roughly to comply with modern code of practice requirements, where joints are required every 12 metres. The local authority was not happy about this proposal. When cracks occur to a building that is 80 years old, questions need to be asked about what has changed. It transpired that a row of conifers that had shaded the wall had been removed in 1987 after the hurricane. A brick pavior path that now runs the length of the building alongside the long wall had replaced a gravel path perhaps five years ago. The drains had been inspected and found not to be faulty. The ground conditions were generally non-cohesive material unlikely to be affected by wetting and drying. The architect had carried out surveys as to the plumb of the walls and had found that, particularly towards the end of the building, where there were most cracks in cross walls, there was a significant leaning out of the long wall. When cracks occur in the structure of walls, one considers thermal and moisture movement as well as foundation movement. I walked the length of the long walls and particularly inspected closely the wall facing west, which was fully exposed to the sun. There were no cracks at all of any significance in the long wall or to the return gable at the west end. The internal cracks did not seem to be in any way due to the thermal movement, so I questioned the proposed movement joints in the wall. It was explained to me that the engineer felt that the wall exposed to the sun was being forced to bow out by thermal expansion of the bricks and mortar, and effectively had pulled the cross walls away, causing the cracking in those walls. As I did not know the reason for the cracking and as the engineer had carried out a thorough investigation, I proposed that he and I should meet and decide on a solution agreeable to both parties which, if possible, would avoid the movement joints in the long wall. This might be by providing movement joints in the cross walls or, in extreme circumstances, perhaps dry lining the walls to cover the cracks. I did not consider the cracks to be a danger to the stability of the structure, but their appearance worries the inhabitants of the almshouses. A meeting is being arranged. Brian Morton is consultant to the Morton Partnership. 17
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