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
Professional practical experience for Architects in training
The long process to transform the nature of education and professional practical experience in the Architecture profession following recent reports.
A people-first approach to retrofit
Moving away from the destructive paradigm of fabric-first.
International Electrician Day, 10 June 2025
Celebrating the role of electrical engineers from André-Marie Amperè, today and for the future.
New guide for clients launched at Houses of Parliament
'There has never been a more important time for clients to step up and ...ask the right questions'
The impact of recycled slate tiles
Innovation across the decades.
EPC changes for existing buildings
Changes and their context as the new RdSAP methodology comes into use from 15 June.
Skills England publishes Sector skills needs assessments
Priority areas relating to the built environment highlighted and described in brief.
BSRIA HVAC Market Watch - May 2025 Edition
Heat Pump Market Outlook: Policy, Performance & Refrigerant Trends for 2025–2028.
Committing to EDI in construction with CIOB
Built Environment professional bodies deepen commitment to EDI with two new signatories: CIAT and CICES.
Government Grenfell progress report at a glance
Line by line recomendation overview, with links to more details.
An engaging and lively review of his professional life.
Sustainable heating for listed buildings
A problem that needs to be approached intelligently.
50th Golden anniversary ECA Edmundson apprentice award
Deadline for entries has been extended to Friday 27 June, so don't miss out!
CIAT at the London Festival of Architecture
Designing for Everyone: Breaking Barriers in Inclusive Architecture.
Mixed reactions to apprenticeship and skills reform 2025
A 'welcome shift' for some and a 'backwards step' for others.