Brickwork: Historic Development, Decay, Conservation and Repair
Gerard Lynch
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| Victorian carved and gauged brick pilaster in South Kensington, London with fine joints of lime putty and silver sand, and (below) a similarly gauged brickwork crest carved in situ by the author. |
Previously considered to be an inferior material to stone, brick was rarely used in construction in Britain until the close of the Middle Ages. The popularity of the material can be traced to the revival of brick-making in eastern England in the late 13th and early 14th centuries. This was a direct result of the lack of good local building stone, an increasing shortage of good timber, and the influence of areas of continental Europe where brickwork was used extensively. By the Tudor period the bricklayers and particularly the brickmasons, skilled in working bricks to size and shape post-fired, had emerged as separate craftsmen well able to rival the stonemasons. From unsophisticated early work, brick, as a prestigious building material, entered its heyday, rivalling stone in its popularity as a structural material.
Tudor Brickwork
Bricks were generally made on site in wood, heather or turf (peat) fired clamps by itinerant workers. Not only were standard bricks produced but also many in extravagant and elaborate shapes, epitomised by those that formed the spiral twisted chimney stacks for which the period is renowned. The Tudors further patterned their brickwork by inserting flared headers of over burnt or vitrified bricks into the walling. These dark surfaces, stained by the potash from the wood fuel, ranged from deep purple to slate in colour. They were laid carefully in quarter brick offsets in mainly English bond or English cross-bond, to form a diaper or chequered pattern within the predominantly red brickwork.Tudor bricks were typically irregular in size and shape and therefore thick (15-25mm) mortar joints were necessary to even these out. The slow setting mortar was usually of matured quick lime (often containing particles of the fuel used in its production) and sand slaked together to yield a lime-rich ratio varying from 1:1-1:1.5, the joints being finished flush from the laying trowel, or profiled with a ‘struck’ or ‘double-struck’ profile. The facades typically finished with a colour wash of red ochre_ called ‘raddle’, with the joints picked out to a lesser scale, and a distemper applied with a thin brush in a process called ‘pencilling’. With the building of Hampton Court Palace we have not only the seal of royal approval, but a monument to the achievement of brick in this period.
Dutch Influence in the 17th Century
The use of brick dramatically increased following the Restoration of the monarchy in 1660. The court of Charles II brought new fashions from the Low Countries, including a taste for red brick architecture in particular. Once a prestigious material used by the wealthy for their castles and large mansions, brick became more affordable as production increased, and was increasingly common particularly in the capital city. There brick clay was cheaper and more accessible than building stone, and following the Great Fire of London in 1666, timber-framed construction was no longer acceptable in towns and cities.
The late Stuart and early Georgian periods, particularly between 1670 and 1760, was a high point in the skilful use of brickwork that was aided by big improvements in the manufacture of bricks, the skills of the craftsmen and by a great flowering of architecture under influential designers such as Hugh May (1621-84), Roger Pratt (1620-84), Robert Hooke (1635-1703) and Christopher Wren (1632-1723). Their influence was felt until well into the early 19th century.
A dramatic change in architectural style is evident from the late Gothic and vernacular styles of the Tudor, Elizabethan, Jacobean and early Stuart periods due to the increasing influence of Italy. Until the mid-17th century that influence was largely via Northern Europe, and particularly the Dutch styles. This was made popular by the proliferation of builders’ ‘pattern books’ often used by master builders as artisan architects. This contributed to a style of architecture that lasted up to the Commonwealth (1649-60) known as Artisan Mannerist because of the license the designs take with the rigid rules of Classical architecture. Kew Palace, originally called the Dutch House in Kew Gardens, London (1631) is an important influential example of this style.
From the viewpoint of brickwork technology, the Dutch House is worthy of further comment because it is the earliest known example in England of a whole facade set out and built using correct Flemish Bond – that is to say, one based on alternate stretchers and headers in the same course. It is also a good example of the transition of Gothic-styled enrichments of Tudor and Jacobean buildings to Classical details. These were created by brickmasons skilfully using the brick axe to cut-mould soft rubbing bricks’, post-firing, in an early form of gauged brickwork_ introduced from the Netherlands.
The architect Inigo Jones (1573-1652) looked to Italy to find the source of the Renaissance Classical tradition and to discover important innovations in materials and skills. He spent time there and was the first to become truly conversant with the architectural rules laid down by Andrea Palladio (1508-1580) in his four-volume work, ‘I quattro libri dell’architecttura’ (1570). These gave emphasis to the precise use of Classical ratio and proportion in all aspects of design and detailing. Inigo Jones’s discovery led to the development of the ‘Palladian’ style, and its widespread adoption in Britain and Ireland.
From this point onwards responsibility for the design and control of a new building started to shift from the traditional master builder to the architect, a non-practitioner. Some leading architects, like Hugh May, Roger Pratt, Robert Hooke and Christopher Wren would listen to their craft masters in matters of design detail, materials and application, but by the middle of the 18th century this practice had changed and increasingly architects insisted on master craftsmen interpreting working drawings faithfully with little, if any, room for individual license. This led to buildings being rather style-bound and lacking in the unique vitality created by the masters’ input of former years.
The Georgian Period 1714-1830
From a technical perspective, the late 17th and early 18th centuries were another high point in both brickmaking and their use. Their manufacture was much improved, with blended clay, better moulding and more even firing which led to greater consistency in shape and size. In hugely influential London the colours of bricks changed in popularity: red, purple or grey bricks were fashionable from the late 17th century until 1730, when brownish or pinkish grey stocks replaced the red, or ‘hot’ colours. These were followed in the mid-18th century by grey stocks, and by 1800 the production of yellow marl or malm London stocks, which were closer to the stone colour desired for a Palladian classical facade.
Face brickwork was generally of a very high standard, laid mainly Flemish bond, although header bond was also popular in the early 18th century.
Improvements in the materials and production of mortars also occurred throughout this period. The use of washed and graded aggregates began to appear during the late 18th century, and colouring was often added to pointing mortars. Parker’s ‘Roman’ cement was patented in 1796, and other branded natural cements and stronger classes of hydraulic limes soon followed. An early form of Portland cement, a blend of limestone and clay, fired and ground to make an artificial cement binder, appeared in 1824. These all set quicker and stronger and were vital to the speed of construction that the Industrial Age demanded.
Pointing was executed to a similar standard. As well as giving more protection to the weaker bedding mortar, fine detailing also helped to minimise the visual impact of the joints so that the classical details could be displayed more clearly. The highly skilled craft practice of 'Tuck' pointing was the ultimate development in this quest. A more expensive solution was to use cut and rubbed, and 'gauged' brickwork which was popularised by Wren. This used a facade of fine, colour-matched bricks cut and rubbed to exact units, laid in thin lime putty joints. After 1730 however, this was considered too expensive for complete facades and was generally reserved for window arches, aprons, niches and other architectural ornamentation only.
Victorian Brickwork 1830-1914
The 19th century introduced a period of revivalism in domestic architecture and industrial building. The former, led by architects, ultimately turned to 'medievalism' and other exotic building forms as a relief from the un-spirituality of the Machine Age. The latter, led by engineers, was largely met through the cheap use of bricks for the more utilitarian infrastructure such as factories, warehouses and railway bridges. During this period, more bricks were made and laid than during all the previous periods. Brick manufacturing methods had improved in all areas including quality, accuracy and regularity, and in a larger range of colours available.
From the mid-19th century onwards, the manufacturing process, like many others, was becoming mechanised. This enabled deeper clays to be used for pressing into dense bricks for use on civil engineering works. With improvements in travel and communications, bricks could be transported over wide areas which removed the traditional local variations in building materials, particularly in cities and towns with rail connections. Portland cement continued to develop in quality and strength, and by the second half of the 19th century this binder increasingly took a premier position over natural cements.
A particular factor in its rise was its highly successful use in the construction of the new brick-built sewers in London. Brickwork joints reduced to 0.3 inches (8mm) due to the accuracy of the machine pressed bricks, and continued to be finished in various profiles. These were popular from the 17th century, although the new 'weather-struck' and 'cut' style of joint became particularly popular. A variety of face bonds were now used, although in the main, Flemish bond predominated domestically, while English bond was favoured industrially. In all matters of brickwork, the Victorian desire for enrichment was readily achieved by the use of often garish multi-coloured or ‘polychromatic’ work, and the lavishing of ornamentation by detailing mass-produced, purpose moulded 'special-shaped bricks' or by gauged brickwork.
Decay, Conservation and Repair
Before considering the most appropriate method of repairing brickwork, correct diagnosis of the cause of failure is vital. Manufacturing defects in bricks can be the result of under-firing or impurities in the clay used. These bricks decay more rapidly than better burnt bricks, especially with frost action. They can also act as a point of entry for moisture, which in turn will affect the whole wall, leaving it open to damage from frost and chemical action.
Free standing walls, parapets and retaining walls are particularly vulnerable, and some judicious replacement may be necessary. Sulphate attack can occur when water is present with OP cement-based mortars, producing slow steady expansion of sulphate crystals within the mortar or the bricks as the water evaporates. It is a terminal condition in OPC mortars, and can result in damage and even failure of the masonry. This is particularly common in unlined chimney stacks, where sulphates have been introduced by the burning of sulphur-rich fossil fuels.
Where chimneys have been designed without bends, allowing rain straight down the flue, damp may appear on the chimney breast with a possible resultant salt problem. This can especially occur when the air is humid, or where the fireplace has been sealed without proper ventilation.
Recommended Reading
RW Brunskill, Brick Building In Britain
Victor Gollancz Ltd, London, 1990 Historic England
Practical Building Conservation Earth, Brick and Terracotta, Ashgate 2015
M Jenkins, Traditional Scottish Brickwork, Historic Environment Scotland, 2014
G Lynch, Tudor Brickwork, The Building Conservation Directory, Cathedral Communications, 2012
G Lynch, Joint Finishes on Historic Brickwork, The Building Conservation Directory, Cathedral Communications, 2016
G Lynch, Hot-mixed lime mortars and traditionally constructed brickwork, The Journal of The Building Limes Forum, 2017
G Lynch, Brickwork History, Technology and Practice, Rutledge, 1994
G Lynch, The Colour Washing and Pencilling of Historic English Brickwork, Journal of Architectural Conservation, Donhead Publishing, 2006
G Lynch, The History of Gauged Brickwork, Elsevier, 2007 N Lloyd, A History of English Brickwork, H Greville Montgomery, London, 1925
