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For centuries bricks were moulded by hand in wooden moulds. These were four sided and rectangular in shape with no base or lid. Moulds were placed either directly on the ground or on a roughly made brickmakers table. Bricks made on the ground are generally pre 19th cent. They were known as 'place' bricks and often contain grass impressions. From the 19th cent rectangular block of wood, smaller than the mould dimensions, would be screwed on the table which created the brick's 'frog'. Sometimes letters were carved in the frog to identify the brickyard owner. With the advent of steam power brickmaking became mechanized wherever volume justified it. Steam driven extrusion plants with nine overhead wire cutters produced ten bricks every few minutes.One of the oldest methods of firing is by clamp. A clamp is a temporary construction of unfired or green bricks which is dismantled after firing and could be erected near the clay source. Clamps varied from yard to yard but there were general rules which most followed. The floor had to be level and was made of burnt brick. Channels were often made in the floor and filled with fuel, usually breeze (crushed coke) but any fuel would suffice and wood, furze, charcoal were also used. Next came three or four layers of green bricks which were placed on edge and then another layer of fuel was added. After this, green bricks were packed closely together to a height of 14 or 15 feet. The bricks were 'dished' or tilted inward to prevent injury to workmen during firing. Sometimes the outside was sealed with wet pug. Most clamp bricks had a small percentage of breeze added to the clay during manufacture. This helped to 'self fire' them and ensured that a good temperature was reached. Clamps contained 30,000 to 150,000 bricks. An average size would take two or three weeks to burn out, although larger ones could take as much as ten or twelve weeks. Updraught kilns may be as old as clamps. These were known as Scotch kilns and were permanent structures with one or more firing chambers.The kilns were built of burnt brick. Flues ran under the perforated floor from one end to the other. Green bricks were stacked on the chamber floor with small gaps between them to allow the heat to circulate. The open top was covered with old burnt bricks and turf or pug to help conserve the heat and prevent draughts that would cause uneven firing. The kilns had to be stoked regularly day and night for at least three or four days. It was quite common to see flames rising from the top of these kilns when firing. The death knell sounded for many small yards in 1939 when Blackout Regulations were brought into force. A later development came to be known as a Suffolk kiln. These were fired on the same principle but smaller and set into a bank. One reason for this was to provide ease of access for loading or setting, another was for insulation. The downdraught kiln was far more efficient than the Scotch or Suffolk. Firing was much easier to control. They were often circular in structure with about eight fire holes. Inside the fireholes were baffles or 'bag' of firebricks. It had a domed roof and a perforated floor under which ran a flue leading to the chimney stack. The circular or 'beehive' kiln had a capacity of about 12,000 green bricks. Coal was lit inside the firehole grates and hot gases were directed upward from the baffles and then downwards from the underside of the dome and through the stacked bricks by the draught from the chimney. Altogether it took fourteen days or so to operate, with two days for loading or setting, three days for 'curing', two days for heating to full temperature, one day at full heat, then another three or four days to cool down and a further day to unload or draw.

Sydney, Mar 23, 2010 (ABN Newswire) - Brickworks Limited (ASX:BKW) announce, Australia's leading brick company Austral Bricks(TM), today unveiled Australia's largest tribute to US President, Barack Obama, at Horsley Park on the M7, despite the postponement of his visit. Austral Bricks(TM) went ahead with the 100 square metre construction of the mural in the lead-up to the visit and following the postponement was announced, added the sign "Where the bloody hell are ya?" The wall will be still in place in June, the next scheduled date of the president's much anticipated visit. More than 6,000 glazed bricks were laid over a five day period by J&M Langon Bricklayers and features Austral Bricks(TM) Burlesque(R) and Dynasty(R) ranges. Austral Bricks' national marketing manager, Brett Ward said, "We decided to finish the construction of the wall and the sign with our tongues firmly in our cheeks. We are using Aussie humour as a token of the friendship between our two countries and commemorate the 70th anniversary of our alliance. "We hope our humour is taken the right way by our friends in the US and we will take down the sign as soon as the president steps foot on our shores mid-year", he added."The Brick Art(TM) mural demonstrates the versatility and contemporary nature of what can be achieved with bricks. Austral Bricks is excited about the opportunities that Brick Art(TM) can play in the creation of unique and interesting murals for architects and designers", said Mr Mark Ellenor, NSW General Manager of Austral Bricks.The Barack Obama wall is the latest Brick Art(TM) mural by the company, following on from the Michael Jackson Tribute that was built in September last year. The glazed bricks used in the mural are in colours not normally associated with bricks, including green, white, blue, leather and black from both the Burlesque(R) and Dynasty(R) ranges. Seven of the 10 available brick colours were used to create the impressive art piece.

Madonna To Lay Bricks Of New Malawi School

2:31pm UK, Monday April 05, 2010 Hazel Tyldesley, Sky News Online

Madonna has arrived in Malawi to lay the first brickof a new school funded by her charity, which supports poverty-stricken children in the southern African country. Madonna and her adopted children during a visit to Malawi last year.The Raising Malawi Academy for Girls promises to be a family and support centre, allowing female students to attend regular classes as well as giving them access to medical care and regular meals."The Academy will be much more than just a school — in a country where one million children have been orphaned due to Aids, the Academy will educate, protect, and empower young girls," the charity said.

Madonna will be joined by economist Jeffrey Sachs, a development affairs expert who recently entered the debate over the so-called Robin Hood tax, saying it could help boost aid to Africa.The first item on the pop singer's itinerary in Malawi is a trip to a UN community initiative called the Millennium Village, which promotes sustainable development. Madonna has donated millions of pounds towards projects in Malawi and has also adopted two children from the impoverished nation.She won a court battle that had initially blocked her adoption of toddler Mercy James last year, but met criticism from children's charities that suggested the girl could be better cared for in her home country.The singer's £10m centre, located on the outskirts of the country's capital Lilongwe is set to open in 2011.

21 February 2010 7000-year-old bricks discovered in China

Bricks dating back 5,000 to 7,000 years have been unearthed in northwest China's Shaanxi Province, adding between 1,000 to 2,000 years onto Chinese brick-making history, archaeologists claimed. "The five calcined bricks were unearthed from a site of the Yangshao Culture Period dating 5,000 to 7,000 years ago. Previously, the oldest known bricks in the country were more than 4,000 years old," Shaanxi Provincial Institute of Archaeology researcher Yang Yachang said. Only parts of the bricks, including three red ones and two gray ones, have been recovered, Yang said.

Yangshao Culture is a Neolithic culture that flourished along the Yellow River, which runs across China from west to east. The culture was named after Yangshao, the name of the first village discovered of the culture, in 1921 in central China's Henan Province. Archaeologists used to believe the ceramics were applied to architecture in the Shang Dynasty (1600 BCE-1100 BCE), which had been proved wrong by the new discovery, Yang said.

The smooth surface and rough surface of most well preserved red bricks are vertical to each other, and the rough surface was designed to be stuck to other materials, Yang said. "It is still unknown whether the bricks were in a square or rectangle shape as none of them are complete," he said.

The site, covering an area of more than 200,000 square meters, was to be cut through by a new highway, said Shao Jing, assistant researcher of the institute. The salvage excavation was launched in August 2009. As of February, more than 2,300 square meters had been excavated, Shao added. More than 150 sites, including houses, ash pits, ash grooves and kilns, had been found in the area, Shao said. "The bricks were all discovered in ash pits, which were garbage containers for the ancient people. For the modern archaeologist, these garbage containers are treasure troves of artifacts," she said.

The world's oldest unearthed bricks date back 8,000 to 10,000 years. They were discovered in Middle East and they were adobes which had not been calcined. Thus, the brick-making history of human kind should be about 10,000 years, Yang Yachang said.

Source: CRIemglish (20 February 2010) http://www.stonepages.com/news/archives/003731.html

by Stephanie sd249707@ohio.edu March 1st 2010

Bare on the Bricks was not a normal fundraising event. If you were anywhere near Court Street, a5hens county in the US on Saturday at noon, you know that. Hundreds of people ran down the busy street in barely anything for a great cause. The event's overall goal was to raise funds and donations of clothes for local Athens clothing banks and the relief efforts in Haiti.

A seven-year-old boy, Roman, sorts bricks at the Sadat brick factory in Kabul where he works every day from 8am to 5pm. Child labour is common in Afghanistan's brick factories where adult workers, desperate to make more money, enlist their children to help with some of the easier jobs.

Stone is a material of variety, nuance and unrivalled durability. Used appropriately and with regard to its nature it can enhance the architectural style of a building and last thousands of years. Geological Consultant, Francis Dimes of www.BuildingConservation.com outlines the geological characteristics of the material and the principles of its selection for use in conservation and restoration work

Often considered the aristocrat of building materials, stone is arguably the traditional building material of Great Britain. Stonehenge, of a quartzitic sandstone known as sarsen, dates back to about 1800 BC, a lasting testament to its durability. Yet this was a relatively late arrival compared with the magnificent limestone temples of Malta which date back to before 4000 BC, or the stone houses near Jericho, constructed in about 6000 BC.

Any rock, anywhere, has been used for building if only on a restricted local scale. A study of the geological map of Great Britain shows that the country has a great variety of rocks. But not every rock may be used successfully. Thought must be given to its weathering properties and to its nature, which may allow the rock to be worked to a fine surface and detail. It follows that some knowledge of the local geology will be of help in understanding the relationship of a building, the country in which it stands and the stone of which it is built.

Any stone can be placed geologically (and thus scientifically) into one of three groups. Only when the nature of the rocks in these groups is known can the stone be properly used.

Igneous rocks are those which cooled and consolidated from a fluid melt (magma) of rock material. The magma may have cooled quickly to give fine-grained rocks or slowly, to produce coarse-grained crystalline rocks. The nature will depend also on their chemical composition.

Many have been found in Great Britain, but only one - granite - has been used on any scale. South-West England and Scotland are the great granite producing areas for building.

Sedimentary rocks were originally deposits of sediment (the eroded material from pre-existing rocks) laid down, mostly, on old sea-floors. When compacted and cemented, sedimentary rocks result. Their composition depends on the nature of the original sediment, but only sandstones (composed of quartz grains) and limestones (chiefly of calcium carbonate) have been used on any scale. In general terms, limestone predominates in southern Britain and sandstone in the north, but some limestones such as Portland stone have been used ubiquitously; and some sandstones, for example York stone are widely used especially for paving.

Metamorphic rocks result from the modification of pre-existing rocks by heat, pressure or both. The one which has been most widely used in Britain is slate. Other indigenous metamorphic rocks have been little used. Slate is found chiefly in Scotland, the Lake District, North Wales and Cornwall.

There are constraints inherent in stone which demand that the material is properly used in accordance with its unique characteristics. Igneous rocks may contain minerals which on exposure to the atmosphere may break down with consequent damage to the stone. Rising salts, also, may cause spalling. Of prime importance with sedimentary rocks is the placing of the bedding plane so that it is at right angles to the thrust imposed upon it. Metamorphic rocks may have deleterious (harmful) minerals present. The greatest restraint in the use of stone is that of the jointing. All rocks are jointed and the size of a block that can be wrought from a quarry is controlled by joints.

Such constraints are minor compared with the benefits: Stone from all these groups, whether used in classical idiom or in contemporary form, will have a durability other materials cannot match, provided it is properly chosen and properly used.

STONE FOR CONSERVATION AND RESTORATION WORK

The first requirement when a stone building is considered for conservation or restoration is to determine the nature of the stone. Many historic buildings will have archival records which should be scanned for references to the source. Where that does not produce any answers a geologist should be consulted to determine the nature of the stone. The next stage, the determination of the 'provenance', the source of the stone, may be much more difficult. Again it is best referred to a geologist with specialist knowledge of the geology of stone for building and decoration.

Once the provenance is established (which may not always be possible), a search of the area for still working quarries then follows. Those quarries in Great Britain known to be producing dimensional stone are listed in The Natural Stone Directory (see Recommended Reading). If the stone is still available, can it be obtained within the time-frame for restoration?; and can it be obtained in suitable sizes? It must also be recognised that stone from a present day quarry, whilst geologically the same, may in fact present a slightly different appearance from stone quarried in the past. Nevertheless, to preserve the integrity of the building, the same geological stone is always to be preferred.

However, it is not always possible to find the stone required. In that event a geologically appropriate stone should be sought, and the re-use of original or reclaimed stone should be considered. Although many masons object to 'second-hand' stone, there appears to be no scientific reasons why the material should not be re-used, provided that bedding and other criteria are observed.

The matching of stone from a provenance other than the original is a specialist task. Again, advice should be sought from geologists with experience in this field. It may be necessary at this stage, for thin-sections to be cut for microscopical study, or for X-ray diffraction techniques to be used. Guidance will be given by the specialist.

 Brickwork: Historic Development, Decay, Conservation and Repairhttp://www.buildingconservation.com/articles/brick/brickwork.html

Gerard Lynch

Previously considered to be an inferior material to stone, brick construction was rarely used in Britain until the close of the Middle Ages. Gerard Lynch looks at its historical development over the last 600 years and its conservation and repair.

TUDOR BRICKWORK 1485-1603

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 lack of local stone, an increasing shortage of good timber, and the influence of Europe where brickwork was used extensively.

By the Tudor period the brick-makers and bricklayers had emerged as separate craftsmen well able to rival the masons. From unsophisticated early work, brick building entered its heyday, rivalling stone in its popularity as a structural material.

Bricks were generally made on site in wood, heather or turf 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 renown.

The Tudors further patterned their brickwork by inserting headers of over burnt or vitrified bricks into the walling. These dark surfaces ranging from deep purple to slate in colour, 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 irregular in size and shape and therefore thick (15-25mm) mortar joints were necessary to even these out. The slow setting mortar was of matured non-hydraulic lime (often containing particles of the fuel used in its production), and coarse sand in a ratio varying from 1:2-1:5, the joints being finished flush from the laying trowel.

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.

THE GEORGIAN PERIOD 1714-1830

The late 17th and early 18th centuries were a high point in the use of brick. Their manufacture was much improved, with blended clay, better moulding and more even firing which lead to greater consistency in shape and size. The colours of bricks changed in popularity from red, purple or grey bricks fashionable in the late 17th century until 1730, when brownish or pinkish grey stocks replaced the 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 classical facade.

Brickwork was generally of a very high standard, in mainly Flemish bond although header bond was also popular in the early 18th century.

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. 'Tuck' pointing was the ultimate development in this quest.

A more expensive solution was to use 'gauged' brickwork popularised by Wren using a facade of fine, colour-matched bricks cut and rubbed to exact units, and laid in thin lime putty joints. However after 1730 this was considered too expensive and was reserved for window arches, aprons and other ornamentation only.

VICTORIAN BRICKWORK 1830-1914

This was a period of revivalism in domestic architecture and industrial building. The former seeking a return to 'medievalism' and other exotic building forms as a relief from the unspirituality of the Machine Age. The latter, for the infrastructure of factories, warehouses, railway bridges and so on, all largely met through the cheap use of bricks.

During this period, a greater number of bricks were made and laid than during all the previous periods. Brick manufacturing methods had improved in all respects including quality accuracy, regularity and in range of colours available. From the mid 18th 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.

Improvements in the production of mortar also occurred during the late 18th century through the use of washed and graded aggregates, often with colouring. Also, the development of natural cements including Roman cement and other hydraulic limes, which set quicker and stronger, were vital to the speed of construction that the Industrial Age demanded. Portland Cement appeared in the mid 19th century.

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, whilst English bond was favoured industrially.

In all matters of brickwork, the Victorian desire for enrichment was readily achieved by the use of often garish polychromatic work, and the lavishing of ornamentation by detailing mass produced purpose moulded 'specials' 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.

Poor Detailing can also contribute to failure through construction defects such as:

• Decayed bond timbers, joists, timber lintels, plates or bearers which have been embedded or built in to the masonry.
• The expansion of rust on corroding iron and steel structural members, wall ties or reinforcement embedded in the brickwork.
• Failure of arches and lintels from inadequate bearings, or abutments.
• Poor bonding and inadequate or even non-existent tying-in of brickwork. This can be due to a habit in the 18th and 19th centuries of 'snapping' headers leading to a wall of two skins, instead of one mass. Alternatively failure can occur at the junctions between walls, particularly where front and rear walls are insufficiently tied to the cross walls.
• 'Corbelling' (over projecting brickwork) and oversailing are especially prone to being insufficiently tailed-in to the main walling. They are also susceptible to water penetration due to inadequate, or non-existent protective weathering.
• Sulphate attack occurs when water is present with cement based mortars, producing slow steady expansion of sulphate crystals within the mortar or the bricks as the water evaporates. It 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.
• Poorly designed parapet copings without damp proof courses, inadequate overhangs, and poor jointing techniques, which encourage damp penetration.

• Consolidants should only be applied to decaying brickwork as a last resort. Although predictably effective on soft porous bricks their use is still in its infancy, and the long term affects of new techniques is less certain. The consolidated brick face may behave in a different manner from the base through thermal movement, resulting in eventual separation.
• Sealants may induce similar problems. By sealing the surface they may inhibit or reduce surface evaporation leading to a build up of moisture. This can result in concentrating evaporation in other areas where crystallisation and frost damage may be exacerbated. Sealants should only be used in localised areas to prevent problems such as the staining which occurs from water run-off from limestone dressings, where it may be used after removal of the deposits.
• The introduction of hard mortars is one of the most common causes of failure in historic brickwork, leading to a failure of the mortar and of the brickwork itself.

Vegetation although often attractive, is generally harmful to older brick walls of traditional construction. Many types of ivy can cause serious damage to brickwork particularly if it is in poor repair, or constructed of soft, possibly spalling, bricks bedded in soft lime mortar where the pointing is defective.

If not carefully removed, ivy should at the least, be heavily controlled and never allowed to reach eaves level where it might block gutters and downpipes. In a strong wind, vegetation can also transfer additional wind-load, pulling out guttering, parapets, and even a chimney-stack.

Pigeons can also present problems, especially in city centres. Not only can they force up loose roof coverings, but they will block up gutters and downpipes with feathers, detritus and excrement, causing water penetration and consequent decay. The faeces rapidly deface the external (as well as internal) fabric, and may damage porous brickwork. Removal is difficult and expensive.

Control is therefore imperative, and can involve bird nets, repellent gels, poisons, traps and even shooting.

Recommended Reading

• · J Ashurst and N Ashurst, Practical Building Conservation, Volume 2: Brick, Terracotta and Earth, Gower Technical Press, Aldershot, 1988
• · TG Bidwell, The Conservation of Brick Buildings, Brick Development Association, Windsor, 1977
• · RW Brunskill, Brick Building In Britain, Victor Gollancz Ltd, London, 1990
• · N Lloyd, A History of English Brickwork, H Greville Montgomery, London, 1925
• · GCJ Lynch, Gauged Brickwork: A Technical Handbook, Gower Technical Press, Aldershot, 1990
• · J Woodforde, Bricks To Build a Brick House, Routledge & Kegan Paul, London, 1976

Clay-tiled Roofs

Stephen Boniface and Tony Redman

http://www.buildingconservation.com/articles/claytile/claytile.htm

There is plenty of evidence that the Romans used clay tiles extensively on their properties. Although the use of clay tiles diminished somewhat during the Saxon period, by the 12th century there are records of clay tile use being encouraged particularly in place
of thatch for fire safety. The size of tile (10½" x 6½" x ½") was standardised in 1477.

In the early years the use of clay tiles, like many other building materials, was limited by cost. Nonetheless, for those who could afford it, clay tile was often the material of choice.

Another limiting factor was transport. Prior to the advent of mass transportation systems it was rare for clay tiles (or any other materials) to be transported any significant distance, typically not more than a day’s cart journey. Exceptions were made for the roofing of churches and the homes of the very rich, who often had access to clay fields and kilns further afield, and employed the labour, which made the costs much cheaper.

As a result the pattern of clay tile usage correlates closely with the areas in which clay and ‘brick earth’ are found, and it is perhaps not surprising to find that the manufacture of clay tile from the later medieval period was closely aligned to that of brick-making.

By the late medieval period a more stable social, economic and political climate resulted in an increase in wealth, generally enabling more people to afford materials such as brick, glass and indeed clay tiles.

From the 17th century clay tile became the ubiquitous roofing material for large parts of the country where the raw material was close at hand – mainly the southeast and east of England and the Midlands.

Greater wealth in the 19th century, improved transportation and the introduction of taxation on fired building products such as tiles and bricks to fund the Napoleonic wars led to a reduction in the use of clay tiles and the increasing use of other roofing materials, particularly slate. However, it was the advent of the railway more than anything else that caused the roof map of England to change from red to grey. During the 19th century slate tended to be cheaper and thus it overtook clay tiles as the roof material of choice for the rapidly developing urban landscape.

During the 20th century mass-production of machine-made clay tiles resulted in a resurgence of clay-tiled roofs, particularly during the inter-war period. However, increase in competition from man-made tiles such as concrete tiles and man-made slate resulted once again in a downturn in the use of natural clay tiles. In more recent years homeowners have rediscovered the beauty of the material and there has been something of a resurgence in the use of handmade clay tiles.

The tile typically found throughout this period is the double-lap tile (one where the overlap between courses of tiles is greater than the length of a tile) but one should not forget the single-lap tile where the tiles interlock at edges only. Although today we are used to seeing the single lap tile in the form of concrete roofing materials, the history of single lap tiling goes back many centuries. The most common form is what we generically refer to as ‘pantiles’. These should not be confused with genuine Roman tiling, which in fact has not reappeared in any significant manner in this country since the 4th century AD.

The use of pantiles is not as widespread as clay tiling generally and it tended to focus on the eastern side of the country. Records indicate that pantiles arrived somewhere around the 17th century, with home-produced pantiles appearing from about 1700. Because the tiles were originally imported, their distribution tends to focus on the ports of the eastern seaboard. The exception is Bridgewater in Somerset, where pantiles were certainly established by the late 1750s and where a prolific pantile-making industry later emerged, supplying tiles throughout Somerset and the neighbouring counties.

MANUFACTURE

The manufacture of clay tiles is relatively straightforward. Traditional handmade tiles are a mixture of clay with aggregates rolled out and cut or moulded to simple rectangles (sometimes shaped) with two holes at one end for fixing. These are then fired in a kiln. Sometimes the ends were extended at right angles to form a nib, but the majority of clay roofing for many centuries was simply a baked clay rectangle.

Due to the firing, flat tiles would come out slightly convex and this added to their character. Uneven temperatures in the kiln and the nature of the hand-making process also contributed to variations in shape and form, and the quality of the clay resulted in rough and therefore textured surfaces. The colour would be determined partly by the clay and the mix of aggregates but also by the temperature and length of firing in the kiln.

Sometimes shaped tiles were produced and occasionally glazed tiles and pantiles can be seen. During the Victorian period there was much experimentation and occasionally one comes across multi-coloured examples. With modern machine-made tiles, dyes are added to bring greater consistency of colour.

FIXING

Plain clay tiles are laid in regular courses with each tile lapping two others, leaving approximately four inches exposed. The precise method of fixing depends on the nature of the tile itself. In the case of the more basic form of tile, simple tapered wooden pegs were pushed through the two holes at the top of the tile so that the tile could be hung over battens fixed horizontally across the tops of the roof rafters. The tops of the pegs would be trimmed flush to the surface of the tiles so that the next course would lie flat.

Lime mortar, sometimes with straw and other aggregates, would often be applied to the internal face of the tiles to fill the gaps and help improve the general fixing of the tile. This mortar fillet is often referred to as ‘torching’. On many roofs the pegs would be limited to only one per tile. Indeed, roofs can often be seen with no pegs at all, or at least pegs only in occasional courses. Although this can be due to the pegs rotting away, sometimes tiles were laid bedded in lime mortar with no pegs. In such
situations the fixing of the tile relied as much on friction and the weight of tiles above as on any torching or mortar bed.

If a tile had been made with nibs these would be used to hang the tile over the batten, and pegs would not be required. With modern tiling the nibs themselves have holes to enable nail fixing to the battens, although not every course is nailed in place.

As the use of slate increased, the need for nails to fix them also increased. The consequent increase in the production of nails resulted in their increasing use to fix clay tiles as well: nailing was quicker and avoided the need to trim the timber peg before laying the next course.

Today we find a wide variety of tiles available to us, including traditional peg tiles but also handmade tiles with nibs to facilitate fixing.

TYPICAL DEFECTS AND REPAIRS

It is often said that clay tiles have a limited life of up to 60 years or thereabouts. However, walking around the countryside you will often come across peg-tiled roofs that are several hundreds of years old, so this is clearly not a reliable guide.

The failure of the tile itself will depend on many different factors, including the original manufacture, the make-up of the material within the tile and its firing in the kiln.

Because tiles are much thinner in section than brick, they are less susceptible to variations in firing. Nonetheless, there will always be some tiles that are from the cooler parts of the kiln and therefore more vulnerable to early failure, particularly as a result of frost damage. That said, as a rule handmade tiles tend to have great durability and, if well-fired, tend not to be particularly vulnerable to frost damage. Only after many years will the best examples eventually weather, exposing the softer and more porous clay body below to frost damage.

Other factors which can influence the longevity of tiles (and, in fact, any roof covering) will be the orientation of a building, the steepness of the roof and indeed the microclimate around the building. Clay tiles are best used on roof pitches of 40° but some single lap tiles can be used down to 25° pitches.

Other more controllable factors include such matters as tree branches brushing up against the roof covering and dislodging or breaking tiles, climbing plants being allowed to grow over and into tiling to dislodge and damage it, and clumsy workmen treading on the tiles.

Due to the rough texture of a clay tile surface it is likely to harbour lichens and mosses. These plants should not necessarily be regarded as harmful. Although lichens produce acidic secretions and moss can hold moisture and lead to frost damage, they are unlikely to cause much damage. Indeed moss can provide a protective layer and lichens contribute to the characteristic colouring of tiled roofs. However, significant moss growth can increase the weight on the roof structure generally, and when it dies and rolls into the gutter it can cause quite serious gutter blockages.

If moss is to be removed, care should be taken. Simply pulling moss from the roof surface is more likely to cause damage than by letting it die naturally or by appropriate chemical removal means (biocidal treatment). However, care should be taken with chemical removal methods to ensure that the chemicals do not run down to the gutter and into the surface water system.

The defects that most often affect tiled roof coverings are in fact the sort of defects that affect all roof coverings: failure of battens (rot, woodworm etc); failure of the batten fixings (nail corrosion); deterioration of the tile fixings (rotting pegs, corroding nails or crumbling torching); failure of or defects to the roof frame; defects to perimeter details (soakers, flashings, etc); defects to roof details (valleys, verges, eaves, etc); and wind uplift.

Problems that can affect the tile surfaces, apart from those rare occasions when moss or lichen cause damage, are usually brought about by matters such as pollution, the premature failure of poor quality tiles, saturation from leaking pipes or drips from overhanging details such as TV aerials.

Frost damage can occur where moisture is retained on the surface and this sometimes happens at the laps. Sometimes localised frost damage can cause a tile to break at the head lap. Machine-made tiles are particularly prone to frost damage as the surfaces are more even and regular, enabling moisture to be trapped on the underside. Handmade tiles on the other hand have a natural variation which is both less moisture-retentive and more pleasing to the eye.

Other problems can arise due to poor laying in the first instance. Such problems include inappropriate detailing at verges and hips, poor setting and laying of the ridge and poor detailing of abutments such as chimneys and walls. Abutments need particular care. Local vernacular may dictate the use of tile creasings, or else mortar fillets, or lead. Lead flashings are usually the more reliable and mortar fillets the least. Whichever detail is used, lead soakers should always be incorporated between each tile to resist the passage of rainwater horizontally.

Another common failure with clay-tiled roofs is brought about by the failure of the fixings or battens due to rot or rusting. The battens often use sapwood, which is much more vulnerable to decay than heartwood. Pressure-treated battens should always be used for repair and replacement. If care is taken, many of the tiles themselves can usually be salvaged and reused. A word of warning, however: because peg tiles tend not to be pegged every course and therefore rely on friction and/or the torching, there is a risk of mass failure and slippage if a careless roofer steps onto the roof. Before attempting to repair a clay tile roof it is important to check the fixings below in case the attempt at repair itself causes more damage.

When repairing a tiled roof it is important to obtain as close a match as possible to the original in terms of texture and colouring. Non-ferrous fixings should be used to reduce corrosion risks. Any lime torching should be continued across new areas of work, and with the existing torching properly reinstated.

Most roofs can be satisfactorily patch-repaired rather than having to be completely stripped and re-covered. However, if complete re-covering is to take place, every attempt should be made to salvage the tiles and as a rule of thumb one would hope to salvage approximately 70 per cent.

Complete stripping and re-covering requires the new work to comply with building regulations, and this would often mean the use of a lining over the rafters beneath the battens and tiles. Such linings restrict airflow into the roof space, and the roof space then has to be positively ventilated or a modern breathable lining used.

It should be noted that where there is a double-lap roof covering, a lining is not strictly necessary for weathering purposes. Homeowners often attempt to line a roof because they believe it to be appropriate or perhaps to stop unnecessary draughts. However, attempting to line a roof from the underside (within the roof space) can lead to a number of problems. Because the lining is then not laid over the rafters it will direct any penetrating water into the eaves where it will cause rot and damage. Careful thought and installation is needed with regard to retrospective lining and it is best avoided.

In recent years there has been an increase in the use of expanded foam applications to the undersides of tiles. These are often marketed as providing a solution to insulation problems, securing loose tiles in place and reducing draughts. However, the use of such material should be viewed warily and it is suggested that such material should be regarded as a last resort only, particularly for historic buildings. Foam stuck to the underside of the tiles means the tiles cannot be salvaged for re-use at a later date. The practice also makes it very difficult to undertake patch repair in future because of the difficulty in getting individual tiles out. There is also a possibility of reducing the life of the tiles or slates if they are a bit porous, as it reduces the evaporative surface area: water absorbed when it rains will no longer be able to evaporate from the lower surface. The risk of frost damage is therefore greater.

Spray-on foams also perform poorly as a means of insulating roofs. The blocking up of ventilation and the lack of a moisture barrier can lead to condensation problems. Building regulations require a ventilation gap above insulation or a vapour membrane under the insulation, but with spray-on foams neither are provided.

From an aesthetic point of view these foams can also be a problem, as it is often difficult to prevent the foam spilling out between gaps in the tiles (particularly pantiles). Such foams are therefore a short-term form of repair that could increase the long-term cost of later work. If tiles are slipping it is better to undertake a proper repair.

Of course these negatives should always be balanced against the difficulty of access and perhaps the expected future lifespan of the roof. If the building is listed, however, such work would require consent and many conservation officers would probably refuse consent for use of such products.

Traditional clay tiles create beautiful roof coverings that are full of character due to the individual nature of the tiles. Provided they are carefully and properly maintained there is no reason to expect them to perform poorly. Many of the typical problems found can be resolved without loss of the tile itself. Before embarking on any work to a roof seek professional advice on what is required. If altering or extending the roof of a listed building, ensure the appropriate consent has been obtained.

An Inspirational Story with Wisdom
Stopped By A Brick
by Author Unknown

About ten years ago, a young and very successful executive named Josh was traveling down a Chicago neighborhood street. He was going a bit too fast in his sleek, black, Jaguar, which was only two months old. He was watching for kids darting out from between parked cars and slowed down when he thought he saw something. As his car passed, no child darted out, but a brick sailed out and - WHUMP! - it smashed into the Jag's shiny black side door! SCREECH...!!!! Brakes slammed! Gears ground into reverse, and tires madly spun the Jaguar back to the spot from where the brick had been thrown.

Josh jumped out of the car, grabbed the kid and pushed him up against a parked car. He shouted at the kid, "What was that all about and who are you? Just what the heck are you doing?!" Building up a head of steam, he went on. "That's my new Jag, that brick you threw is gonna cost you a lot of money. Why did you throw it?"

"Please, mister, please...I'm sorry! I didn't know what else to do!" pleaded the youngster. "I threw the brick because no one else would stop!"

Tears were dripping down the boy's chin as he pointed around the parked car. "It's my brother, Mister," he said. "He rolled off the curb and fell out of his wheelchair and I can't lift him up." Sobbing, the boy asked the executive, "Would you please help me get him back into his wheelchair? He's hurt and he's too heavy for me."

Moved beyond words, the young executive tried desperately to swallow the rapidly swelling lump in his throat.

Straining, he lifted the young man back into the wheelchair and took out his handkerchief and wiped the scrapes and cuts, checking to see that everything was going to be OK. He then watched the younger brother push him down the sidewalk toward their home. It was a long walk back to the sleek, black, shining, Jaguar - a long and slow walk.

Josh never did fix the side door of his Jaguar. He kept the dent to remind him not to go through life so fast that someone has to throw a brick at him to get his attention.

Don't let the bricks in life hit you, be sensitive to those around you

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