Building from Tradition

Local Materials and Methods in Contemporary Architecture

Elizabeth M. Golden

• Verlag: Routledge
• Jahr: 2017
• ISBN:
  9781317437284
• Auflage: 1
• Thema: Architettura
• Thema: Architettura generale

Building from Tradition examines the recent resurgence of interest in the handmade building and the use of local and renewable materials in contemporary construction. In the past, raw materials were shaped to provide shelter and to accommodate the cultural, social, and economic needs of individuals and communities. This is still true today as architects, engineers, and builders turn once again to local resources and methods, not simply for constructing buildings, but also as a strategy for supporting social engagement, sustainable development, and cultural continuity.

Building from Tradition features global case studies that allow readers to understand how building practices—developed and refined by previous generations—continue to be adapted to suit a broad range of cultural and environmental contexts. The book provides:

• a survey of historical and technical information about geologic and plant-based materials such as: stone, earth, reed and grass, wood, and bamboo;

• 24 detailed case studies examining the disadvantages and benefits to using traditional materials and methods and how they are currently being integrated with contemporary construction practices.

Part 1
Material Fundamentals

Part I serves as an introduction to the most significant mineral and plant-based resources traditionally used for construction. Earth and stone are featured in Chapter 1, and Chapter 2 covers reeds and grasses, wood, and bamboo. Both chapters provide an overview of the history, properties, and recent production methods of each material, which is intended to enhance the reader’s understanding of the case studies featured in Part II of this book.

1

Geologic Materials

1.1 Mud brick ice house in Iran.

Earth

Earth is an essential resource: the Urstoff, or primary matter, of human existence. In all probability, it has been endowed with more cultural significance than any other material. As the ground under our feet, it connects us with place and to geologic time. As soil, it hosts plant life and provides nourishment. In some cultures, it is even considered to be alive, instilled with the presence of deities or linked to biological processes, such as aging. It has often been used as a metaphor for new beginnings: a pure and shapeless substance ready to be molded into new forms.¹

Earth’s cultural meanings are also varied. Earth has paradoxically been deemed sacred and profane, precious and common, valuable and worthless. Although it is at times associated with luxury and health, earth is frequently denigrated as a material to be used by only the poorest members of society. The stigmatization of earth has led to a decline in its acceptance as a building material, and its unreliable and ‘dirty’ image seemingly contradicts its previous significance as a solid and desirable medium for building permanent shelter.

Soil, when mixed with water, was a ‘transformative technology’ during the Neolithic period. This newfound material formed the basis for sedentary living, and its malleable qualities allowed for easy transformation—a process that quite literally reshaped the landscape into some of civilization’s earliest permanent dwellings. Soil also determined the location of domesticated crops, and the material was fashioned into vessels for carrying water to the fields as well as to the building site. Soil was an important resource that changed the way people lived and interacted with their environment; as archeologist Nicole Boivin observes, “humans shaped soil, so it likely shaped them and their world.”² Easily adapted to the needs of its occupants, the basic earthen dwelling persisted and multiplied to form larger communities and, for many civilizations, these eventually expanded to become some of the first significant urban settlements.

Often these ancient cities were constructed from unfired mud bricks. According to archeological records, the earliest use of the material was in the walls of Jericho. There, mud bricks formed round houses dating from around 8000 BCE.³ Mud bricks also contributed to the growth and evolution of the ancient city of Mehrgarh in Pakistan, where evidence suggests they were in use as early as 7000 BCE.⁴ Visible examples of earthen urbanism still survive—a testament to the material’s longevity. The Ziggurat of Ur, which stands in present-day Iraq, is constructed from mud bricks and is a remnant of the Mesopotamian city founded in 4000 BCE. In Peru, adobe walls that formed the foundations of Chan Chan, a pre-Columbian city that flourished between 850 and 1470 CE, cover an area of approximately 6 square kilometers. The city of Agadez in Niger became an important trading center on the edge of the Sahara during the fifteenth and sixteenth centuries and many of its banco or mud brick buildings from this time are still in use today. Chan Chan, Ur, and Agadez demonstrate the global relevance and ubiquity of earthen construction for numerous societies across many eras.

1.2 Contemporary rammed earth house in Arizona, USA.

1.3 Traditional mud brick house next to contemporary concrete home in Al Huwayah, Oman.

Composition and properties

The product of erosion, soil is composed of rock that has been gradually worn down by physical, biological, and chemical processes. The type of ‘parent’ rock and the method by which it has been eroded gives soil its inherent characteristics. These inherent properties influence how soil, transformed into a building material, performs when used in construction.

Feldspar erosion and the decomposition of other silicate containing minerals form the base material for clay. Despite their microscopic size (0.0001–0.004 millimeters), these particles and their associated binding properties are of central importance to the builder. Clay molecules consist of hexagonal layered sheets (lamellae) that are bound up into packets. An electrostatic charge occurring between the outer layers of these packets is primarily responsible for the cohesive capacity of the material, making clay very different from cement and other substances that depend on a chemical reaction to activate their binding properties. Clay’s binding properties are activated by water. The material swells as moisture is absorbed between the lamellae and shrinks as moisture evaporates.

1.4 Agadez, Niger.

Soil used for construction is a mixture of clay, silt, and sand; sometimes it also contains small stones. Clay acts as the binder, while silt, sand, and stones are aggregates, which give the mixture its compressive strength. Each type of construction, be it mud brick or rammed earth, relies on varying percentages of these ingredients. Compaction is the most common method used to improve the compressive strength of the material. Beating or ramming moist soil causes the particles to vibrate, allowing them to settle into a more ordered, compact structure. Compaction is integral to rammed earth construction, which involves filling formwork with successive layers of loose soil and pounding them until they solidify. The outcome is a dense, monolithic material that is particularly well suited for exterior loadbearing walls.

One drawback of earthen walls is that they are not water resistant, making them susceptible to damage from moisture and frost. Because of this, most structures constructed from earth are typically plastered or protected by a wide roof overhang, in addition to being raised off the ground on a dampproof foundation. Earth’s thermal storage capacity, however, is significant and has been exploited for centuries. Massive earthen construction provides a buffer against outdoor temperature fluctuations; its capacity to absorb, store, and radiate heat allows it to temper the indoor ambient environment. Earth walls keep rooms cool in summer and warm in winter. They can also maintain comfortable indoor humidity levels. The clay minerals present in the material are hygroscopic, absorbing and releasing moisture as it fluctuates with internal activities and external weather conditions. The moisture absorbed can also enhance the material’s heat storage capacity.

Traditional methods

Earth construction technology advanced at different rates and at different times, and the selection of earth as a building material can be attributed to particular climate variations and the availability of certain resources. Earth-based construction was most prevalent in areas where other resources were scarce, and practices were adjusted to respond to diverse weather conditions and the availability of water. Water is essential for the production of mud bricks, just as rainless periods are necessary for drying the material. Both of these factors limit where bricks can be produced, making this technique more common to river deltas in arid regions. Rammed earth construction, by contrast, depends on damp soil excavated straight from the ground and typically requires little or no additional water. This technique was not limited by humid weather conditions, and can therefore be found across a wider range of climatic and geographic zones.

1.5 Rammed earth construction.

When used as a building material, earth presents several challenges. Mud tends to crack when drying, and the spanning capacity of the material is limited due to its low tensile strength. While the plasticity of the material can be useful, it can also slow construction. To overcome these deficiencies, builders often added other locally available materials to either strengthen or work in tandem with earth. In order to prevent cracking, straw was frequently incorporated as reinforcement, and certain substances, such as plant extracts, naturally occurring bitumen, lime, and animal blood, were all found to improve the durability and water resistance of earth construction. Roofs and wall openings were spanned with wood or bamboo elements, when available, and in cases where these resources were scarce, earth masonry vaults and arches were formed as an alternative. To systematize and streamline earthen construction, builders also employed other materials as formwork. Forms for making bricks, typically made either from wood or bundled reeds, required a minimal amount of material. More substantial formwork was necessary for rammed earth construction, necessitating greater quantities of wood.

Archeological evidence confirms that almost every type of soil has been used for building. Some soils, however, proved more suitable for construction than others. These were either sourced directly or combined with other soils to achieve desirable characteristics for building. As with concrete, soil used for construction combines aggregate of various sizes (gravel, sand, and silt) with a binder (clay). The proportion of these el...