The Building Conservation Directory 2023

99 C AT H E D R A L C O M M U N I C AT I O N S T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 2 3 | C E L E B R AT I N G 3 0 Y E A R S M A S O N R Y 3.2 locally as can be seen in the illustration above. Also as one moves from one period to the next these choices reflect changing architectural styles, materials and craft practices. For example, stone copings reflecting the local geology can be found on Stuart, Georgian and Victorian brick walls in areas with good building stone where brick was a late arrival, particularly where the local stone could be easily split into flags and coping stones. In areas where the locally available stone was poor, brick and terracotta copings and cappings are likely to be most common. Both plain and ornamental terracotta designs were popular, although standard bricks laid in a variety of configurations, and particularly specially shaped bricks, purpose-moulded to shed water, were very highly favoured. As all copings and cappings will suffer periods of saturation, in former times suitable locally-made bricks were selected by empirical knowledge and pragmatic experience, to minimise the risk of frost action and, in some cases, the liberation of soluble salts too. Today, local knowledge and experience is supplemented by selecting clay bricks known to be suitable for designated exposure levels ranging from ‘sheltered’ or ‘moderate’ exposure to ‘severe’ or ‘very severe’, according to which part of the country you are working in. Modern bricks must satisfy declared frost-resistance ratings of F2 (which is the highest of three categories – F0 being non-frost-resistant and F1 being moderately resistant), and a declared soluble salt content designated of S2 (the category with the lowest active soluble salt content). Although it is important to complement the original brickwork, generally brick copings and cappings should be dense, preferably with a smooth finish to repel the water, or engineering bricks should be used. Copings and cappings come in three basic shapes: • Saddle-back or ‘twice-weathered’ • Feather-edged, ‘splayed’ or ‘once-weathered’ • Half-round – or ‘segmental’. STONE COPINGS AND CAPPINGS Traditionally, stone copings and cappings were fully bedded in a lime-rich mortar applied straight onto the topmost course of bricks, but modern codes of practice deem that they should be bedded on a specified type of flexible DPC, such as high-bond bitumen polymer, to prevent moisture movement seeping down into the brickwork below through micro cracks that might develop within the connecting cross joints. Polyethylene DPCs are prohibited because they will not bond with the mortar leading to displacement of the masonry above. Nonetheless, where any DPC is used it is essential to prevent a slip-plane by sandwiching the full width of the DPC between two beds of mortar, and by immediately bedding copings or cappings onto it to gain maximum action and bond strength. Adding weight A ‘brick-on-edge’ capping to an 1898 free-standing garden wall A ‘Staffordshire blue’ coping detail of saddlebacks set on plinth mouldings, d 1910 A fired clay ‘saddleback’ coping on an 1875 brick wall and (right) a detail of its throating Roof tiled copings are common: left, two bonded courses of clay ‘creasing tiles’ set with fine mortar joints and surmounted with ‘half-round’ ridge tiles laid in mortar; right, several courses of roof tiles topped with ridge tiles, set in mortar. (All Photos: Gerard Lynch) on top will also help with adhesion. All connecting cross joints should be fully- and tightly-jointed to ensure solidity and to minimise the possibility of cracking: and the joints should be finished flush. For extra security the copings or cappings are sometimes fixed together with non-ferrous cramps set into appropriately sized pre-cut slots in the top, particularly on sloping sections of walling. BRICK COPINGS AND CAPPINGS Historically, clay bricks have been used very successfully for copings and cappings on free-standing walls. Frequently these were the local brickmaker’s special-shaped bricks, often bespoke-made and oversized to suit the designer’s requirements. The advent of a nationwide network of canals and then railways saw the introduction of more robust bricks for this purpose across the UK, like the famous ’Staffordshire blue’ engineering brick. Transport improvements also saw stronger classes of building limes becoming more widely available too. COPINGS AND CAPPINGS FROM STANDARD BRICKS The artistic skill of traditional bricklayers is sometimes seen on the finish to thick- walled construction through the careful manipulation of standard bricks, set to bond at 45o, to form an attractive saddle-back coping; the stopped-ends of which demand great accuracy and skill to measure, cut and set to terminate the brickwork correctly. In later years a more basic brick-on-edge became popular, comprising evenly-sized bricks set to gauge, laid with fully-filled joints, termed ‘buttered’ within the craft, when applied from the trowel onto the brick held in the