A wall is a vertical structure that encloses a space, defining an area of land. It can be either external or internal. As part of a building, walls carry loads and provide support to roofs, floors, and ceilings. Another purpose of walls are to ensure shelter, security, and soundproofing for users within a defined space. Walls can also be representative of boundaries and borders as part of a defense system. There are multiple types of walls in terms of function and materiality, such as: masonry, concrete, wood-frame, partition, and load-bearing to name a few.
Walls have been built since ancient civilizations for protection, like the Sumerian walls (2000 BC) and the Great Wall of China (7th century BC onwards). Romans constructed Hadrian's Wall (2nd century AD) in Britain. Medieval times saw castle walls for defense. The 20th century featured ideological walls, such as the Berlin Wall (1961-1989). Presently, walls serve various purposes including security (e.g. Israeli West Bank barrier), separation (e.g. peace walls in Northern Ireland), and common walls in buildings for privacy and structural support. The US-Mexico border wall also remains a significant and controversial contemporary example.
As of September 2021, the Great Wall of China is often considered the longest, but not the tallest. The tallest walls are typically retaining structures, such as the Diga del Vajont in Italy, which stands at 262 meters (860 ft). For inhabited structures, the Ryugyong Hotel in North Korea stands as a wall-like skyscraper at 330 meters (1,080 ft). The Israeli West Bank barrier is one of the tallest security walls, reaching heights of 8 meters (26 ft) in places.
Walls are versatile structures that can be classified into various types based on their function and construction. Load-bearing walls are integral to a building's structure, supporting the weight above them, while partition walls are used to divide spaces without bearing any load. Shear walls are crucial in providing lateral support to buildings, particularly in earthquake-prone areas. Retaining walls are engineered to hold back earth and maintain different levels of soil. Boundary walls define property lines and offer security. Additionally, cavity walls consist of two parallel walls with an airspace in between for insulation, and veneer walls are non-structural, providing a decorative surface.
In the future, walls are likely to become more adaptive and multifunctional. Smart walls with integrated technology could regulate temperature, lighting, and even display information or images. Modular and movable walls may facilitate adaptable living spaces. The use of sustainable materials like rammed earth or recycled plastics could be prevalent. Transparent solar panels might be integrated into walls for energy generation. Additionally, advances in 3D printing technology could revolutionize how walls are constructed, making it faster and more cost-effective.