BOMEL Slaughterhouse / BAEB Bureau d’Architectes Emmanuel Bouffioux
BOMEL Slaughterhouse / BAEB Bureau d’Architectes Emmanuel Bouffioux
Allenmoos Schoolhouse II / Boltshauser Architekten AG
Allenmoos Schoolhouse II / Boltshauser Architekten AG
63 Compton Street / Doone Silver Architects
63 Compton Street / Doone Silver Architects
The Curving House / JOHO Architecture
The Curving House / JOHO Architecture
Chapel of St.Lawrence / Avanto Architects Ltd
Chapel of St.Lawrence / Avanto Architects Ltd
House Stein / Jan Rosler Architekten
House Stein / Jan Rosler Architekten
The History of Bricks and Brickmaking
Man has used brick for building purpose for thousands of years. Bricks date back to 7000 BC, which makes them one of the oldest known building materials. They were discovered in southern Turkey at the site of an ancient settlement around the city of Jericho.
The first bricks, made in areas with warm climates, were mud bricks dried in the sun for hardening.
Ancient Egyptian bricks were made of clay mixed with straw. The evidence of this can be seen today at ruins of Harappa Buhen and Mohenjo-daro. Paintings on the tomb walls of Thebes portray Egyptian slaves mixing, tempering and carrying clay for the sun dried bricks.
The greatest breakthrough came with the invention of fired brick in about 3,500 Bc. From this moment on, bricks could be made without the heat of sun and soon became popular in cooler climates.
The Romans prefered to make their bricks in spring, then they stored them for two years before selling or using them. They only used white or red clay to manufacture bricks.
The Romans succeeded in introducing fired bricks to the entire country thanks to mobile kilns. These were bricks stamped with the mark of the legion who supervised the brick production. Roman bricks differed in size and shape from other ancient bricks as they were more commonly round, square, oblong, triangular and rectangular. The kiln fired bricks measured 1 or 2 Roman feet by 1 Roman foot, and sometimes up to 3 Roman feet with larger ones. The Romans used brick for public and private buildings over the entire Roman empire. They built walls, forts, cultural centre, vaults, arches and faces of their aqueducts. The Herculaneum gate of Pompeii and the baths of Caracalla in Rome are examples of Roman brick structures.
During the period of the Roman Empire, the Romans spread the art of brickmaking throughout Europe and it continued to dominate during the medieval and Renaissance period.
When the Roman Empire fell, the art of brickmaking nearly vanished and it continued only in Italy and the Bizantine Empire. In the 11th century, brickmaking spread from these regions to France.
During the 12th century bricks were reintroduced to northern Germany from northern Italy. This created the brick gothic period with buildings mainly built from fired red clay bricks. The examples of the Brick Gothic style buildings can be found in the Baltic countries such as Sweden, Denmark, Poland, Germany, Finland, Lithuania, Latvia, Estonia, Belarus and Russia. This period lacks in figural architectural sculptures which had previously been carved from stone. The Gothic figures were virtually impossible to create out of bricks at that time, but could be identified by the use of split courses of bricks in varying colours, red bricks, glazed bricks and white lime plaster. Eventually custom built and shaped bricks were introduced which could imitate the architectural sculptures. In the 16th century, Brick Gothic was replaced by Brick Renaissance architecture.
In medieval times, the clay for making bricks often was kneaded by workers with their bare feet. They clay was shaped into brick by pushing it into a wooden frame placed on a table, which was covered with sand or straw to prevent the clay from sticking. After excess clay was wiped off with a stick, the brick was removed from the frame.
In England the remains of buildings prove that the art of brickmaking was highly advanced by the time of Henry VIII. After the great fire of London in 1666, the city was rebuilt with mainly bricks.
Adobe brick, which is sundried brick made of clay and straw, has been made for centuries in Central America, particularly in Mexico. Some Aztec adobe structures still exist, one example is the Pyramid of the Sun, built in the 15th century.
Bricks crossed the Atlantic with Dutch and British immigrants with some brickmasons among them. In Virginia brick structures were built as early as 1611. At that time it was common for brickmasons to make the bricks on the jobsite. It is known that bricks were transported from Virginia to Bermuda in 1621 in exchange for food and oil.
Many early American skyscrapers are clad in brick or terracotta. It took 10 million bricks to build the Empire State Building.
During the Renaissance and Baroque periods, exposed brick walls became less and less popular, consequently brickwork was covered in plaster. Only during the mid 18th century brick walls started to regain their popularity.
Bricks were made by hand until about 1885. Once the Industrial Revolution broke out, the brickmaking machinery was introduced. Consequently, the number of clays that could be made into brick was greatly increased which influenced the production capacity. Handmade brick production ranged up to 36,000 bricks per week but by 1925 a brickmaking machine made 12,000 bricks a day.
As brick structures could be built much quicker and cheaper, they replaced other raw materials like stone or rock.
During the building boom of the 19th century, when more than 10 billion bricks were produced annually, many American cities like Boston and New York favoured locally made bricks.
In Victorian London, due to the heavy fog, bright red bricks were chosen which made buildings much more visible. Although the amount of red pigment was reduced in bricks production, red remained the most desired colour for the brick and still does to this day.
It was used by some of the 20th century’s most famous architects like Le Corbusier, F. L. Wright and Louis Khan.
Nowadays, apart from wood, bricks seem to be commonly used building material. Consequently, brick and terracotta architecture is dominant in its field with a great development in brick industry.
Arches
The arch has long been used in masonry structures. In fact, a brick masonry arch found in the ruins of Ur in Mesopotamia dates back to 1400 B.C. Today, the brick arch is used in construction to span over wall openings and add aesthetics, as the arch is the consummate definition of form and function. This Brick Brief addresses design considerations for brick arches in veneer construction. Common arch terminology is shown in Figure 1. The first important consideration when designing a brick arch is whether the arch is structural or non-structural. That is, will the arch be required to transfer vertical loads to abutments or will it be fully supported by a steel angle. While this may seem obvious, confusion often develops because of the many configurations of arch construction.
Introduction
The arch has long been used in masonry structures. In fact, a brick masonry arch found in the ruins of Ur in Mesopotamia dates back to 1400 B.C. Today, the brick arch is used in construction to span over wall openings and add aesthetics, as the arch is the consummate definition of form and function. This Brick Brief addresses design considerations for brick arches in veneer construction. Common arch terminology is shown in Figure 1.
The first important consideration when designing a brick arch is whether the arch is structural or non-structural. That is, will the arch be required to transfer vertical loads to abutments or will it be fully supported by a steel angle. While this may seem obvious, confusion often develops because of the many configurations of arch construction. To answer this question, one must consider the two structural requirements necessary for a brick arch to adequately carry vertical loads. First, vertical loads must be carried by the arch and transferred to the abutments. Second, vertical load and lateral thrust from the arch must be resisted by the abutments. If either the arch or the abutment is deficient, the arch must be considered as non-structural and the arch and its tributary load must be fully supported by a steel angle or plates. Alternately, reinforcement may be used to increase the strength of either or both the arch and the abutments.
Structural Arches
Figure-1.-Arch-Terminology
Technical Notes 31, 31A and 31C address the structural design of brick masonry arches. Design methodology and example calculations are provided for jack, segmental and semi-circular arches. The reader should refer to these Technical Notes for specific design recommendations. This Brick Brief discusses structural arch design requirements with respect to common arch problems.
The Arch. There are three failure modes of an unreinforced brick arch: rotation of the arch about the abutment, sliding of the arch at the skewback, and crushing of the masonry. Rotation occurs when tension develops in
the arch. Tension can be reduced by increasing the depth or rise of the arch. If tension develops in the arch, reinforcement can be added to resist the tensile forces. Sliding of the arch will depend on the angle of skewback (measured from horizontal) and the vertical load carried by the arch. Reinforcement can be added to avoid sliding at the skewback, as the reinforcement acts as a shear key. Crushing will occur when compressive stresses in the arch exceed the compressive strength of the brick masonry. If compressive stresses are too large, the arch must be redesigned with a shorter span or a greater arch depth. Compression failure seldom occurs.
The Abutment. An abutment is typically a column, a wall, or a combination of wall and shelf angle. If a shelf angle is used to abut the arch, the shelf angle must be attached to a non-combustible material. Failure of an abutment occurs from excessive lateral movement or exceeding the flexural, compressive or shear strength of the abutment.
Lateral movement of the abutment is due to the horizontal thrust of the arch. This thrust develops in all arches except a catenary arch. The flatter the arch, the greater the horizontal thrust. This thrust must be sufficiently restrained so that lateral movement of the abutment does not cause cracking in the arch or its collapse.
A common lateral movement problem found in residential construction occurs when a porch arch spans between columns. These columns are often constructed of solid brick masonry or wood studs with brick masonry surround. The column is typically designed based on axial load requirements, overlooking horizontal arch thrust. The arch thrust causes the column to deflect laterally resulting in collapse of the arch. The solution to this problem is to stiffen the columns, provide an adjacent wall, or provide a tie between the columns.
Non-Structural Arches
Non-structural arches require support by other elements. Many arches used today are non-structural, built purely for aesthetics. Structural support of the arch may be required because of insufficient arch or abutment strength or the lack of a structural analysis of the arch. Support is provided by a lintel which spans the opening or by a shelf angle which is attached to non-combustible materials. Design recommendations for steel lintels are given in Technical Note 31B.
Expansion Joints
Expansion joints in brick masonry can cause problems when arches are used in the building. Residential construction often does not require expansion joints because continuous wall runs are short. However, if an expansion joint is required near an arch, care must be taken not to affect the integrity of the arch. This is a common problem for very long arches or runs of multiple arches along column abutments.
Vertical expansion joints should not be placed in the area directly above a structural arch. This region of masonry is in compression, so an expansion joint would simply close, causing vertical deflection and possible collapse of the arch. Also, vertical expansion joints should not be placed in the abutment near the arch. This is because the expansion joint will allow lateral movement of the abutment due to arch thrust, possibly causing the arch to collapse. For the particular case of multiple arches closely spaced, vertical expansion joints should only be placed at the ends and at a sufficient distance away from the end of the arch span so that horizontal arch thrusts are adequately resisted.
Flashing
In residential construction, the presence of eaves, overhangs and small wall areas above openings will reduce the potential for water penetration at arch locations. However, flashing at an arch is just as important as over any other wall opening. Flashing an arch can be difficult, depending on the type of arch and the type of flashing material.
Jack arches are the easiest to flash because they are flat. Flashing may be placed below the arch on the window framing for structural arches or above the steel lintel for non-structural arches. Alternately, flashing may be placed in the mortar joint above the arch or keystone. Attachment of the flashing to the backing and end dams should follow standard procedures.
A segmental or semi-circular arch is more difficult to flash properly. This is because flashing materials such as metal flashings are very rigid and may be hard to work around a curved arch. See Brick Brief „ Stepped Flashing” for a detailed solution to flashing a segmental or semi-circular arch.
Construction Concerns
Both structural and non-structural arches must be properly supported throughout construction. Premature removal of the temporary support for a structural arch may result in a collapse of the arch. This is most often due to the introduction of lateral thrust on the abutment before proper curing has occurred.
Out-of-plane bracing is required for all arches. In veneer construction, it is provided by the backup material through the wall ties. Arches that are not laterally braced may require increased masonry thickness or reinforcements to carry loads perpendicular to the arch plane.
Arches may be constructed of special shapes or regular units. Mortar joints may be tapered with uncut regular units. Alternately, regular units may be cut to maintain uniform joint thickness. In general, use of speciallyshaped brick that result in uniform joint thickness will be more aesthetically pleasing. Many brick manufacturers offer such specially-shaped arch units.
Rules of Thumb for Veneer Arches
The following is a list of rules of thumb which may be used when designing structural veneer arches.
Jack Arches
- Six foot maximum span without a lintel.
- Larger skewback angle with longer span
- Skewback = 1/2 in. per ft (4 mm per 100 mm) of span for each 4 in. (102 mm) arch depth
- Camber of 1/8 in. per ft (1 mm per 100 mm) of span
- Minimum arch depth of one unit length, not rowlock only
- Abutment length equal to: span length for one surface, 1/2 span length for two surfaces (see Fig. 2)
Segmental Arches (Less than half circle)
- Rise/span ratio between 0.15 and 0.5
- Make skewback angle as small as possible
- Increase arch depth for better performance
- Wall height above spring line at least 1.3 times arch radius
- Abutment length equal to:
- 0.66 times span length for one surface
- 0.33 times span length for two surfaces (see Fig. 2)
Semi-Circular Arches (Half circle)
- Arch depth as small as 1/2 brick length
- Wall above should be at least (0.9)(Span) from spring line
- Abutment length equal to:
- 0.4 times span length for one surface
- 0.2 times span length for two surfaces (see Fig. 2)
Figure-2.-Surfaces
Note: In order to qualify as two surfaces, the abutment must extend up to the crown of the arch. Also, combination wall and steel angle abutments have only one surface.
Brick Briefs are short discussions of a particular topic. The information contained herein is based on the experience of Brick Industry Association technical staff and must be used with good technical judgment. Final decisions on the use of this information must rest with the project designer and owner.
Monica Adams
Monica Adams
Bekkering Adams
Monica Adams is co-founder and co-director of Bekkering Adams Architects... read more
Juliette Bekkering
Juliette-Bekkering
Bekkering Adams
Juliette Bekkering is co-founder and co-director of Bekkering Adams Architects... read more
