Terracotta
Terracotta translates from Latin as ‘burnt earth’ and is a type of clay-based ceramic or earthenware material that has been used for sculpture, pottery and architectural purposes by many civilisations, from the ancient Greeks, to the Egyptians, the Chinese and Native Americans. The Chinese and Indian cultures used terracotta as a form of elaborate roof decoration for temples and other prestigious buildings. It was also commonly used for buildings in Victorian England, and the American architect Louis Sullivan used terracotta to create ornamentation designs.
It is formed by a mixture of clay and water that is fired and then either be left unglazed, or painted, slip glazed or glazed. If terracotta is to be painted, gesso (a type of primer) is applied first.
Terracotta can be used structurally or non-structurally on both the exterior and interior of buildings. Some of the typical uses that terracotta has had in construction include; chimney pots, air bricks, copings, planters, water and waste water pipes, roofing tiles and shingles, capitals and other architectural details and ornaments.
Terracotta is formed by moulding an appropriate refined clay to the required shape by pouring or pressing it into a plaster or sandstone mould and leaving to dry. It is then placed in a kiln and fired, typically at around 1,000 °C. The characteristic red-brown colour of terracotta is the result of the iron content in the clay reacting with oxygen during the firing. The terracotta is then slowly cooled and finished.
The performance of terracotta is influenced by its porosity. It has poor resistance to tension and low shear strength but is strong in compression.
Terracotta can fail due to; poor manufacturing or installation, weathering, atmospheric pollution that causes salt formation, freeze-thaw cycling, and so on. Poor installation can be due to improper loading, or the mortar used being too strong, which transfers stress to the terracotta block.
By the 1920s, a process known as mechanised extrusion was capable of mass-producing terracotta blocks in standard forms for flooring, roofing and cladding applications. However, it could not compete with more modern building materials such as concrete, structural steel and plate glass, and the changing aesthetic preferences of minimalism and Modernist architecture meant that its use declined throughout the 1930s.
See also: The history and conservation of terracotta.
[edit] Related articles on Designing Buildings
- Brick.
- Ceramics.
- Ceramics at The Building Centre.
- Clay.
- Conserving terracotta.
- Construction materials.
- Earth building.
- Earthen construction.
- Mortar.
- Practical Building Conservation: Earth, Brick and Terracotta.
- Sanitaryware.
- Shelter.
- Sustainable materials.
- The history and conservation of terracotta.
- Terrazzo.
- Tessera.
- Unfired clay masonry: An introduction to low-impact building materials.
Featured articles and news
Heat pump announcements, what homeowners need to know
An 'ultimate guide to heat pumps' from a heating company.
Construction contract awards reach £7.1bn in February
Their highest level in seven months.
The journey to sustainability in heritage
Research is the key to better understanding.
Heritage approaches to adaptation, mitigation and loss.
Bridging the gap between policy, finance and installation.
Development on brownfield land
Definition, background, policy and the latest consultation.
With the Design Framework for Building Services.
Retrofit of Buildings, a CIOB Technical Publication
Pertinent technical issues, measures and the roles involved.
ECA joins HSE campaign to support mental health
Working Minds’ five simple steps based on risk assessment.
Mental health in the construction industry
Mental health issues in brief with related articles.
Transitional arrangements, Building Control and the BSR.
For pre-October buildings with substantial progress by April.
How to write an inspection and test plan
ITPs for quality control and assurance particular elements.
Why quality counts in domestic ventilation systems
From products, to systems to the installation.
Empowering the Future with CIOB Academy
Lifelong learning, upscaling, and reskilling for the built environment.
Winners of the 2024 ASBP Awards
Project, Product and Initiative according to the 6 pillars.