Brick by Brick
or, how St Clement's got built
Building on clay
Unlike in some earlier centuries, by the time the foundations were laid for St Barnabas Chapel in 1820, it was understood that a large building like the church needed deep foundations. Not least in clay, which was the underlying rock type that could shrink and crack. Just look at the north side of St Luke's, Old Street (facing Toffee Park) and you'll see the problems earlier builders had in our part of London. Dug out by hand (legend has it, by French prisoners of war) the trenches went down several metres to provide a solid start to the new building.
In these trenches the first bricks were possibly laid on gravel footings. Products of a burgeoning local industry, these bricks were probably fired locally from clay dug out of the many pits that surrounded London in the 18th and 19th Century. Central Street, just to the east of the church, was formerly known as Brick Lane. And there was even a clay pit recorded at the corner of Lever Street and Goswell Road, where King Square park begins, recorded on 18th Century maps!
Back in the early 19th century brick making began with the preparation of clay to remove large stones and similar contaminates, which was then mixed to the right consistency. A process made easier in the late 18th century with the invention of the horse driven pug mill (an upside down metal cone equipped with turning knives which automatically processed the raw clay).
The clay was then shaped to form bricks by a procedure that was often based on pallet moulding. In this process, a four sided box made from wood or metal with no lid or bottom was placed in front of the brick maker on a base or ‘stock board’. This board had a raised block or ‘lack’ on it to create the hollow, or ‘frog’ conventionally seen on the top surface of the brick. The brick maker would sprinkle the stock board with sand to prevent sticking and then fold his clay mixture into a short fat sausage shape before throwing it into the mould with just enough force to fill it completely and expel any trapped air. He would then use a wire bow to remove any excess clay from the top of the mould before smoothing the cut face with a stick or ‘strike’. Thereafter, a wooden board was placed on top of the mould before it was turned upside down and removed in order to reveal the brick.
Once made, the bricks were turned onto pallets for the slow drying process until ‘white’ hard. This would take about one week in the summer months. At that point they were then ready to be heated to a great temperature - ‘fired’ - to permanently harden them, probably in our case in a ‘clamp’ (a large temporary construction made primarily of the pre-fired bricks and the fuel to fire them). The main advantage of clamp firing was that it could be done on the building site without the need to fabricate a kiln.
When a clamp was made the earth was first levelled, often with old defective, discarded, bricks. Then channels were built across the ground using a combination of first old, and then new white hard bricks, and these were filled with fuel which could be wood, coal or charcoal. Half a dozen layers of newly made bricks were then placed on top and interspersed with more fuel, before finally more un-fired bricks were packed in layers to a total height of 4-5m. The stacking of the bricks was done carefully to aid the passage of superheated air throughout the construction and force air upwards from the channels below. The clamp bricks were not stacked vertically but tilted gently inward and ‘battered’ at the sides to improve the stability of the structure. There could easily be 30,000 to 45,000 bricks in one clamp. The bricks would take from three to twelve weeks to fire, depending on the size of the clamp. Clamps produced a great deal of smoke as well as a foul smell from the initial burning of the organic matter within the clay. People living nearby often complained. It not just 21st century London that had to deal with construction nuisance!
The colour of the brick produced was determined by several factors including the fuel used to fire the bricks and the levels of oxygen available in the clamp during the firing process. However, the most important factor is the chemical composition of the clay. The chemical which most commonly effects the colour of brick is iron oxide, which usually gives the brick a red colour. Blue is produced when iron oxide is present in very high quantities, while if limestone and chalk are added to iron contaminated clay it produces a buff or yellowish colour, as in our bricks. If there is little or no iron or other oxides present in the clay it fires to a white colour.
Bricks were manufactured to a statute which required that they should be twice as long as they were broad, normally being 8 by 4 1/2 inches or 9 x 4 1/2 inches. The long side of the brick is called the ‘stretcher’ face, the short side, the ‘header’ face, while the breadth of the brick when laid is a 'half brick’.
The job of the bricklayer was to select the bricks for use and to lay them, vertically in rows, to a specified height and ‘bond’, a term used to describe the pattern and sequence in which the bricks are laid. Bonding is extremely important, since, for the wall to be sturdy enough to support the structure of the building, bricks were ‘bonded’ into a continuous load-bearing wall rather than acting as a collection of individual bricks. By alternating the use of header and stretcher bricks in different ways, walls could be built with different ‘bonds’. The most common bond at that time – and the one we find at St Clement’s - was the 'Flemish' pattern. Also contributing to effective bonding were good mortar and, sometimes, ‘bonding timbers’ that ran horizontally through the brick courses. The bricklayer jointed and spaced his bricks with pug, a long established generic term used to describe a wide variety of lime mortar mixes. Bricks are traditionally set on a less than 1/2 bed of mortar and this can be cut or ‘struck off’ as laying proceeds, or it can be raked out to about 1/2 in depth and subsequently filled. The effect was, as close as possible, to mimic both the colour and regularity of stone-work. But was much less expensive.
Cleaned around thirty years ago, the brickwork still glows from a distance like a Cotswold stone on a sunny day. Close up, despite the bomb blast damage visible on the south side of the west front, the quality of the work, with its even joints and flushed mortaring, still testifies to the skills of the original workmen.
However, for the most visible parts of the new church the architect insisted on stone, both for the columned portico and for the tower and spire. Like much of the stone used in London buildings in the eighteen and nineteenth centuries, this stone came from quarries in the southwest of England, around Bath and on the Dorset coast at the Isle of Portland.
The excavation of the stone was achieved using a hand saw, ‘plugs and feathers’, a ‘walling hammer’ and a ‘Jadd Pick’. It was heavy and laborious work, which along with the transport cost in the days before railways, made stone an expensive choice for building. St Clement’s building stone probably came by boat to the Port of London or by barge along the Regent’s Canal. Just a hundred metres to the east of the church lay the City Road basin completed around the time the church's foundations were being laid.
The transformation of the stone from hewn block to finished product was undertaken by masons with various levels of skill and might involve the ‘stone mason’, the ‘banker mason’ and the ‘fixer mason’. The skill of the mason when making stone blocks was to ‘dress’ them square and true, so that they would fit together with tight joints of less than 1/4”. Looking at the joints inside the portico of the church even today the quality and preciseness of the work can be easily seen.
Carving stone needs to be of a fine grain, and sufficiently soft to admit easy working, but strong enough to cope with the weather over decades and centuries. The bottom layers of Jurassic limestone are fine grained and therefore suited to carving. The Bath stones of England and the Caen stone of France have often been used for internal work, while Oolitic Limestone is suitable for external carving. St Clement’s has examples of both.
Raising the Roof
A visit up the ladder into St Clement’s roof space you look up into a series of sloping timbers known as rafters fixed, at the top to a ridge board, and at the bottom to a wall plate. Ceiling joists support the ceiling and act as a tie to the rafters - to stop the rafter feet from spreading. In the middle, spaced at intervals, and providing the framework are king post trusses whose beams (the horizontal section) are almost 50cm x 50cm thick. Usually of oak or ash, these massive timbers were discovered to be still in good repair, allowing the roof to be replaced with new slates relatively easily.
Roofers and carpenters worked with hand tools to shape the ends of the beams and joists before they were placed in positions. They were fixed together with iron nails and studs, and the king posts trusses were mortared into prepared slots in the top of the walls. These trusses, 15m from end to end were winched by hand into place!
Roofs in London were usually tiled until the nineteenth century, as thatch was largely forbidden and slate difficult and expensive to bring to London via ship from Wales or south-west England. However, slate had the advantage, for larger roofs, of being thinner and therefore lighter than tile, and improvements to transport (such as the new canal system) meant that slate was much more obtainable and used for an increasing proportion of London buildings by the 1820’s. Quarried for centuries, and still made with wooden mallet and sharpened steel slate-splitting chisel, millions of slates were produced for an increasingly national and international market through the 18th and early 19th centuries. Welsh slate brought from quarries in Snowdonia was most common and was almost certainly used here (see A Welsh Pilgrimage).
These slates were fixed from the base of the roof slopes in descending order of size up to the roof peak, giving a distinctive pattern to the roof slates, used again in the current project. Each slate was secured to horizontal wooden laths with copper ties, each row (course) of slates slightly smaller – but overlapping with – the one below. This is one job that is still done by hand in the 21st century as it was done in the 19th. With skill and precision to prevent any gaps which would let in the elements.
An earlier project in 2008 replaced the asphalt of the internal parapets with stepped lead sheets, carefully designed to drain water into the magnificent cast-iron rainwater hoppers and drainpipes at the church’s corners.
Looking backwards and forwards
The church has now experienced nearly two centuries of London pollution and English weather, been neglected, damaged by wartime bombs and refurbished in the post-War period with sometimes substandard materials. However, those original workmen could certainly be proud that their handiwork had stood the test of time so well. Their skills, honed by generations of architects, surveyors and builders of every specialism building London, served them and us well. With newer techniques (though an equal amount of human skill and ingenuity) we’ve ensured that this handiwork and will be secure for generations to come.