CONTENT

Understanding Material and Technology

(Terracotta Tile & POP)

Reinterpreting a construction method requires an understanding of materials. Through this chapter, an understanding of the properties of the material is attempted along with the origin and transformation of the tile vault technique. The approaches of architects since its origin has been studied with the factors affecting change. The rationale behind most approaches is based on the geometric understanding of the form while in a few cases the form is given more importance.

Project By: Studio Dot

Origin and Evolution

In the 14th century, the process of constructing tile vaults was developed by Moorish builders near Valencia, Spain, which was quite prevalent within the Mediterranean region. The lightweight approach together with an inexpensive method of construction as compared to traditional stone vaulting made the tile vaults a revolutionary solution. The tile vaults were called the boveda tabicada in Spanish. When compared to traditional stone vaulting, tile vaulting uses much less material and can be built way more quickly. Because the slim bricks are laid flat, with the narrow edges in contact, the overall thickness of the vault is a smaller amount compared to conventional masonry, as a result of which, the self-weight and corresponding horizontal thrust are reduced. In the traditional tile vault, the tiles used to be joined with water-based slurry of Plaster of Paris, which sets quickly enough that the inside of the vault doesn’t require any support or formwork from below during the construction process. As against this, a typical stone arch has got to be supported on formwork while constructing and is stable on its weight only when the keystone is in place. By building out from a wall in successive arcs, tile vaulting can be constructed with minimal to no formwork.

In the early 16th century, many Spanish builders were practicing the tile vault method but it was in the late 18th and early 19th centuries that Rafael Guastavino, the Spanish engineer, and architect made a noteworthy contribution by various innovative changes to the traditional method. He described tile vault construction as a cohesive construction method of building that depends on the adhesion of materials rather than the traditional gravity system of constructing vaults. Instead of

(A)

(B)

Fig 1. Comparison of the traditional stone vault (A) and the Guastavino tile vault (B)

https://www.structuremag.org/?p=2046 http://web.mit.edu/cron/Backup/project/guastavino/www/MroszczykMurphy-GuastavinoBPL.pdf

Fig 2. City Hall Subway Station, Rafael Gustavino, 1904

Fig 3. Top View of Sagrada Familia Schools, Antoni Gaudi, 1909

Fig 4. Sagrada Familia Schools, Antoni Gaudi, 1909

http://web.mit.edu/cron/Backup/project/guastavino/www/MroszczykMurphy-GuastavinoBPL.pdf http://www.gaudiallgaudi.com/sagrada-familia-schools constructing a single layer vault, doing another layer with staggering joints and mortar significantly reduces the weight as compared to a similar stone vault and also provides greater load capacity because of the cohesion of materials. Guastavino’s works were first introduced in America through the Centennial Exhibition of 1876 in Philadelphia. In 1881, there was a huge availability of Portland cement in the United States while it had been unavailable in Spain during those times. This gave him the possibility of employing Portland cement with a quicksetting mortar which reduced the construction time and cost drastically. Boston Public Library in 1888 gave his career a push and later in 1889 the Guastavino Fireproof Construction Company was officially incorporated. By 1910, there were around 100 projects of his firm being constructed simultaneously hence making this method known through as the timbrel vault named Rafael Guastavino. Later the method became widely known as the Catalonian way of constructing using tiles.

The laminated tiles were used by many other architects using different approaches and articulation. Antoni Gaudi, Catalan architect, designed certain buildings including the Sagrada Familia School using Catalonian bricks of 29X14X4 cm. Here the base is of the masonry walls and the floor was constructed out of stone to protect the structure from humidity. The three-layered conical vaults are supported by wooden beams that rest on a central metal girder which is a horizontal member from one end of the building to another. Although this school has been constructed using laminated tiles with conical vaults, it cannot be considered a convincing example of a tile vault. Their roof is not self-supporting but is created using beams and steel posts.

Reinterpreting the traditional method of construction and understandings, architects such as Sameep Padora have integrated the form using modern software in such a manner that it weaves the whole space together. The Maya Somaiya Library located in the town of Kopargaon, Maharashtra, is a roof made out of a doubly curved surface that acts as an enclosure without walls. The three-layered brick vault spans 145 feet long and 25 feet wide without being supported by columns or beams. The roof was created using a 3D-modeling program called Rhinoceros to design a structure that gets stability by compression solely. A similar kind of vault has been made and developed by the Block Research Group at ETH Zurich. Although the technique dates back to the 14th century, the various interpretations have led towards a flexible design approach. The primary rationale behind the stability of form remains constant throughout the history of this technique.

Fig 5. Maya Somaiya Library, Sameep Padora, 2018

Fig 6. Terracotta tiles are soaked in water before using construction

Fig 7. Plaster of Paris releases heat when reacts with water

Fig 8. Construction without chicken mesh - Brittle failure

Fig 9. Construction with chicken mesh - Elastic failure

Properties of Materials

Terracotta tiles have been used in various ways in construction such as flooring, cladding, paving, etc. The terracotta tile is mainly comprised of clay and silt. One of the key properties of terracotta tiles is that it is fireresistant. As clay is a mineral that expands when water is added to it. The terracotta tiles are soaked in water before using them for construction so that all the air bubbles get filled with water. Plaster of Paris tends to absorb water which results in a lack of strength of bricks if not soaked well. If the tile absorbs too much water, the lifespan of the structure decreases. Plaster of Paris releases heat when reacts with water. It won’t attain good strength if it does not release heat properly. If it is hard and water comes in contact with it then its quality degrades and it doesn’t bond properly. Once water is added, it sets very fast as a reason for which POP slurry is made in small batches. It is beneficial to wear rubber gloves while working with POP. In the case of cement mortar, cement binds sand when reacts with water. As the terracotta tiles are brittle, a layer of chicken mesh is added between two layers of tiles. If the structure encounters a brittle failure, it might collapse without giving enough time to rescue. By adding chicken mesh, it doesn’t mean that it won’t collapse but the mesh will convert brittle failure into a plastic or elastic failure.

Fig 10. Laminated terracotta tile ( 230 mm X 75 mm X 15 mm)