Summary
Highlights
This lecture is the second part of the first session on architectural materials and will cover the relationship between architecture and materials, with a specific focus on wood. Wood will be discussed over two sessions. Students are encouraged to have their textbooks and notebooks ready to follow along and take notes.
Architectural materials have evolved historically, moving from natural materials in ancient times to artificial materials after the Industrial Revolution. Ancient civilizations used readily available natural resources like wood and stone. The Roman Empire introduced building techniques and materials like concrete, which spread across Europe. The 18th-century Industrial Revolution was a pivotal moment, leading to the invention of cement, reinforced concrete, and steel, enabling the construction of massive, robust buildings. Modern architecture, starting from the 18th century, focuses on glass buildings and addressing environmental issues, demanding materials that support recycling, environmental considerations, and comfortable living spaces. This evolution reflects a shift from purely natural materials to a broader range of engineered materials.
The transition from natural to industrial building materials is visibly demonstrated through architectural examples. Early European classical buildings, often made of natural stone, contrast with later structures that began incorporating industrial materials like bricks. As architecture progressed, buildings adopting concrete for curved forms and steel for high-rise structures like the Shanghai Bank in Hong Kong emerged. These examples highlight a significant change in architectural aesthetics and capabilities due to material advancements.
The concept of “the right material for the right place” (適材適所) is crucial in architectural design. While wood can warp or crack, selecting specific pieces for specific applications can turn these characteristics into advantages. For example, naturally curved wood can be used as an arch beam to support vertical loads effectively. The strong central part of a log is ideal for pillars, while weaker, outer sections are unsuitable. This principle emphasizes proper material selection and placement for optimal structural integrity and longevity, showing how materials' inherent properties can be leveraged for better design.
Architectural materials can be classified based on production, raw material, and application. Production-wise, materials are either natural or artificial. Raw materials are categorized as organic (like wood) or inorganic (like stone or brick). By application, materials serve either as structural elements (requiring high strength and durability, such as wood, steel, or concrete) or finishing materials (prioritizing aesthetics, durability, and safety, like wood, glass, or metal). Understanding these classifications is essential for selecting appropriate materials that meet specific performance requirements in construction.
Architectural materials are used diversely, from stone masonry for walls and flooring to wood serving as both structural and finishing material, as seen in German half-timbered houses and traditional Japanese homes. Modern architecture heavily utilizes industrial products like glass and metal panels for curtain walls, creating contemporary urban landscapes. Quality standards for these materials are indicated by various marks, including JIS, JAS, and environmental labels like the Eco-Mark, ensuring materials meet specific performance and sustainability criteria. Awareness of these marks helps in judging material quality.
The lecture now begins its deep dive into wood, starting from page 4 of the textbook. Wood, being a natural material, has a rich history in architecture worldwide. Its abundance, lightness, strength, ease of processing, and aesthetic appeal have made it a preferred material across various cultures. This section sets the stage for exploring wood's unique properties and its significance in construction, particularly in Japan.
Japanese architecture has a deep-rooted history with wood, dating back to the Jomon period's pit dwellings and raised-floor granaries made entirely from natural materials. The Nara period saw the introduction of large-scale wooden temple construction techniques from the mainland, exemplified by Horyu-ji Temple, the world's oldest existing wooden structure, and Ise Grand Shrine, meticulously rebuilt every 20 years using hinoki cypress. Subsequent periods, such as Heian, Kamakura, Muromachi, and Edo, further developed wooden architecture in residences (Shinden-zukuri, Buke-zukuri, Shoin-zukuri) and castles, all showcasing unique wooden construction methods and sensibilities like wabi-sabi, emphasizing natural beauty.
Japanese architecture is characterized by its post-and-beam construction, utilizing vertical pillars and horizontal beams to form a flexible framework that withstands external forces. In contrast, Western architecture, primarily stone and brick masonry, relies on stacking materials. This results in structural forms like arches, vaults, and domes to create openings and spaces. While Western masonry often limits the size of openings, Japanese wooden structures allow for more expansive open spaces. Understanding these fundamental structural differences is crucial for appreciating the distinct architectural traditions.
While steel and reinforced concrete became prevalent during Japan's modernization, especially for earthquake resistance, wood remained dominant in residential construction. More recently, there's been a renewed appreciation for wood in non-residential buildings. Modern projects, like the wooden town hall in Yakushima, demonstrate innovative uses of wood in larger-scale structures, reflecting a trend towards sustainable and aesthetically pleasing timber construction.
Wood possesses distinct advantages. From a production standpoint, it's widely available in Japan. Materially, it's light yet strong, particularly in tension (even stronger than concrete), easy to process, offers excellent insulation, prevents condensation, and has 'jinsei' (toughness or resilience). Aesthetically, its natural beauty and pleasant texture are highly valued. However, wood also has disadvantages. From a production perspective, trees require significant time to grow, and obtaining long, straight pieces can be challenging, necessitating planned reforestation. Materially, it is vulnerable to fire, susceptible to decay in humid conditions, and not homogenous (containing knots and variations). Its moisture content leads to shrinkage, warping, and cracking upon drying. Though these are drawbacks, understanding them allows for 'the right material for the right place' application of wood.
Understanding wood's internal structure is fundamental. A tree comprises three main parts: the bark (樹皮), the wood substance (木質部) which includes the annual rings, and the heartwood (髄). The wood substance is divided into heartwood (心材), the darker, inner, durable, and less moist part, and sapwood (辺材), the lighter, outer, younger, and more moisture-rich part. The heartwood is highly resistant to decay due to its higher resin and tannin content, with greater strength and less deformation, making it ideal for structural elements like pillars. Sapwood, with its higher moisture content and younger cells, is more prone to shrinkage and warping upon drying. Additionally, wood sections are identified as 'koguchi' (end grain), 'masame' (quarter sawn), and 'itame' (flat sawn), terms critical for understanding how wood behaves and is processed. The base of a tree is called 'motoguchi' (butt end) and the top is 'sueguchi' (tip end), reflecting its natural taper.