C O N T E X T 9 9 : M A Y 2 0 0 7 SUPPORTING COLUMNS Dealing with delaminating walls It is possible to restore the faces of walls that delaminate, writes engineer Brian Morton, but care and ingenuity are necessary. Walls of historic buildings that are constructed of two skins (either of brickwork, stone or flint) which are not bonded together are generally something of a problem when bulges start to appear. On occasions, particularly in Victorian times when churches were re-ordered, a new flint face was applied. Sometimes there was a different, generally harder, mortar mix to the original. No attention was paid to any bonding between the old and the new face. The mortar packed against the old flint was the bonding agent. It had a limited life, of course. Some walls built with a rubble infill, with limited bonding stones through the thickness, are also prone to bulging. If the wall is not to be demolished and rebuilt, the engineer has to come up with a solution to save as much of the existing form of construction as possible. Historically, I have found that problems occur particularly with flint walls which, in this form, are usually built with rubble infill, whether they have been re-faced by the Victorians, or simply rely on the original form of construction. This would normally be perhaps a flint face of 150mm maximum on the internal and external faces. In the case of the east wall of the Suffolk church (pictured above), the wall had been re-faced, probably by a benefactor in Victorian times. The hard mortar and flint material of the external face had allowed water penetration through the cracks, eventually washing the lime mortar backing at the top of the wall down to a lower level of the wall, causing the wall to bulge and subsequently fail. The process seems to be that water gets in, saturating the lime mortar backing, and the sun then shines causing this to dry out, breaking down the lime mortar into dust. This then migrates down behind the face. In the case of a house with a flint face, the gable end was simply constructed of two skins of rubble flint, a The east wall of this Suffolk church had been refaced, probably in Victorian times. Two skins of flint, with a void between them, form the wall of a house.
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