Introduction
Terrazzo can look back on a long history. It was produced as a floor covering as far back in time as ancient Rome and Greece. The material experienced its first comeback during the Renaissance, when the palaces and churches of Venice were decorated with the splendid “Venetian floor”. Less aesthetically pleasing, but all the more sustainable were the terrazzo slabs made from rubble in the post-war period, in particular in Germany. They were often installed in stations and stairways.Terrazzo’s next rebirth began in 2014. Today growing numbers of designers are opting for the sustainable construction material with a speckled look, mixing in plastic, old bricks or construction waste. Some are even designing furniture and accessories in the terrazzo aesthetic.
Terrazzo is a composite material, poured in place or precast, which is used for floor and wall treatments. It consists of chips of marble, quartz, granite, glass, or other suitable material, poured with a cementitious binder (for chemical binding), polymeric (for physical binding), or a combination of both. Metal strips often divide sections, or changes in color or material in a pattern. Additional chips may be sprinkled atop the mix before it sets. After it is cured it is ground and polished smooth or otherwise finished to produce a uniformly textured surface. “Terrazzo” is also often used to describe any pattern similar to the original terrazzo floors.
History
Terrazzo has an interesting history with roots all over the globe. Going back more than 500 years to Italy where marble was the main material of choice. Venetian workers would use scrap marble fragments that they saved from their upscale projects, placing them next to each other in a clay mortar base for their own residence and terraces.Terrazzo is also related to the technique seminato (meaning seed). For this technique, workers would toss large marble chips into the wet cement that was later ground and polished.
Together, these two methods create the generic form of terrazzo that involve pieces of stone that are bonded to a cement bed.While credit is traditionally given to the Italians, as it is commonly recognized that terrazzo was invented by the Venetians, archaeologists have found evidence of such floors in ruins in Turkey dating back 10,000 years ago.
Fast forward to today, and a majority of installations are epoxy-based. Introduced in the 1970s, epoxy soon offered advantages over cement systems, including quicker speeds to install, greater design flexibility, and longer lifecycles. According to the NTMA, epoxy terrazzo is the best thin-set system available, and remains one of the most durable and cost-effective flooring finishes to specify.terrazzo is described as a composite material, poured in place or prefabricated for precast terrazzo which is used for flooring, base, walls, stair treads, countertops, and other custom products.
Material
Terrazzo consists of chips of marble, granite, quartz, glass, shell or other suitable materials. It uses either a cement or epoxy matrix as the binder.Terrazzo is made by combining a cement base (sand, water, and cement) with a mixture of ground minerals – like marble, granite, and quartz – and can be applied to almost any surface, vertical or horizontal. The technique, produced using a completely hand-crafted method, was used worldwide in the construction of modern buildings and is noted for its durability, resistance (to water and abrasion), and easy maintenance.
This made it a go-to material in the creation of flooring for houses and the common areas of residential and office buildings. Terrazzo consists of a mortar made by mixing cement with ground marble. The mixture’s exact composition depends on its use. For example, it’s 50kg of cement to 80kg of marble for floors and 25:40:80 kg for walls (in this case lime is added). Color is added based on a project’s specific requirements and it’s possible to opt for different additives like sandstone, glass, and other stones. It’s always a good idea to consult with suppliers about the properties of each mineral, especially regarding their resistance.
Floors
With a new trend we see new technologies, and today resin systems are revolutionising the design, installation and use of terrazzo surfaces. With these two main options to consider, epoxy-based terrazzo and cementitious terrazzo.
Epoxy terrazzo: The advantage of this flooring type is faster application. Using an epoxy matrix to bind aggregates allows for an incredibly thin-set system that creates a smooth and luxurious floor finish. This system can cure overnight and be ready to polish the next day, permitting a faster project turnaround. This speed of application is ideal for busy shopping centres.
Cementitious Terrazzo: This flooring type uses a cement matrix and describes multiple terrazzo systems, including sand cushion, bonded, rustic, monolithic and polyacrylate systems. This is most suited for exterior and renovation projects. This system is often thicker and heavier.
Installation Steps
- The surface should be washed and clean.
- Plastic or metallic terrazzo divider strips should be placed for each application, ensuring an even surface (the size of the dividing strips should be determined by the granulometry of the stones or the specific project requirements).
- An important detail is that terrazzo facings should be applied using maximum 1.2 x 1.2m panels, contained using rectangular dividers, made of brass, plastic, aluminum, or wood, that will be removed once the terrazzo is laid. It’s a good idea to use a 1x1m modulation to ensure an even result for the facing.
- After placing the dividers, the level layer should be wetted to ensure the facing’s adherence to the base.
- The terrazzo mortar will be applied and spread over the base. When the mixture has higher granulometry, the layer should be compressed using special tools or machines.
- Finally, the terrazzo mortar should be smoothed.
Finishes
Polished Finish:After letting the mixture dry (for 5 to 7 days), the first round of mechanical polishing can begin. Next, the floor should be cleaned completely to apply the stucco, correcting any flaws along the way. Wait another 2 days before removing the excess stucco. On top of this, it’s necessary to do a final polishing, manual or mechanical depending on the project. For the resin application, the floor should be completely clean and dry.
Washed terrazzo: After 2 days, an acid wash should be applied to clean the stones on the surface..
4 types of concrete terrazzo
Sand-cushion terrazzo: This cost-effective terrazzo is primarily used for flooring in the interiors and is extremely versatile. Over the existing concrete slab of the building, an ‘isolation sheet’ is spread, which acts like a base for the galvanised wire mesh. This mesh holds the ‘underbed’ of the terrazzo topping, which is made of sand and cement. Vertical divider strips are placed at regular intervals between the top layer (the terrazzo topping) and the underbed.
The purpose of these strips is to prevent anticipated contraction and to enhance the aesthetics of the colours and patterns of the terrazzo. Considered the best option for spaces where there is a lot of movement and friction, sand-cushion terrazzo flooring absorbs minor defects and prevents their mirroring to the surface. The overall composition will require a 2.5-3 inch slab depression over which the 0.5 inch terrazzo topping would be set.
Layers from bottom to top: concrete slab, thin layer of sand, isolation sheet, wire mesh, sand–cement underbed, 0.5 inch terrazzo topping. Bonded terrazzo can be used in interiors as well as exteriors. In this case, the terrazzo system has only three basic layers – the concrete slab, a layer of mortar and the terrazzo topping. As the name suggests, the slab and terrazzo topping are ‘bonded’ with the help of a sand–cement mortar layer, which is usually around 1.75-2.25 inches.
The mortar easily accommodates the variations or roughness of the concrete slab; hence the quality of the slab is not as critical. Similar to sand-cushion, the terrazzo topping is of a thickness of 0.5 inch.
Monolithic terrazzo: A durable and budget-friendly terrazzo type, monolithic is known for its quick installation time and pricing. Unlike bonded terrazzo, this type depends on the quality of the concrete slab and its flatness. This is because the composition of a monolithic terrazzo is made up of a 0.5 inch-thick terrazzo topping applied directly over the concrete floor. For this composition, a bonding agent is required between the two layers so that the upper terrazzo layer adheres to the concrete and completes the system.
Layers from bottom to top: concrete slab, bonding agent, terrazzo topping.
Rustic terrazzo: As the name suggests, rustic terrazzo has a rough exterior that gives it a rustic feel. This makes it a favourable choice for outdoor areas and spaces like pools and fountains. The texture makes it slip-resistant, which is its unique factor, as other terrazzo types have a smoother finish as compared to rustic. Rustic terrazzo finds its applications in varied areas but requires a 2 inch slab depression for installation. Rustic or washed terrazzo is composed using a non-ground, textured cement matrix topping and this system can be combined with bonded or monolithic types.
Thin-set epoxy terrazzo: This non-cement-based system, has a 0.25 inch or 0.375 inch thick resinous topping applied directly over the concrete floor. Generally, epoxy resin is used, although polyacrylate is also a common substitute. As the name and specifications indicate, the terrazzo is thin and light but extremely durable and strong.
The system is made up of just two layers – concrete floor and resin topping with a flexible membrane in between them to avoid minor cracks. Zinc, brass, or plastic dividers must be installed above any control joints (gaps present in the slab, which allow the concrete to expand or contract when temperatures change) in the sub-floor so that the terrazzo finish does not crack along the joints. Thin-set epoxy terrazzo has high tensile and compressive properties which have advantages like slip and chemical resistance.
Future
Terrazzo decor and fabrics are also very much on-trend: Its characteristic flecks are appearing on shower curtains, bedlinen, sofa cushions, vases, lamps, serving platters, wallpapers and carpets, to give just a few examples. The imagination knows no bounds. What’s more, tiles and furniture fronts can also be decorated with the speckled look at a later stage. The adhesive decor foils in the Meta series by Interprint are astonishingly realistic, but unlike the real thing, they weigh just a few grams. But terrazzo is about more than just design. The material opens up completely new opportunities for sustainability.What was considered dated yesterday can be the foundation for sustainable construction today.
This is certainly how the Berlin design and architecture collective They Feed Off Buildings sees terrazzo. The studio quite literally manufactures terrazzo slabs from old buildings. Founders Luisa Rubisch and Rasa Weber collect construction waste and scrapped marble from gutted or demolished buildings and recycle it into the material they work with, Urban Terrazzo . In this way, resources are conserved, waste reduced, and a piece of urban history preserved.
Terrazzo opens up a host of opportunities for recycling. Construction waste and scrapped rock are just two examples from many possible sources. Plastic in particular makes a good basis, as the TIPTOE coffee table shown above proves. The French furniture manufacturer has set itself the mission of producing sustainable furniture that is built to last. Because after cheap plastic and mass production revolutionised whole branches of industry, the question of what to do with the waste is becoming more and more pressing in the furniture industry, too. Turning it into a material for high-quality furniture – as demonstrated with terrazzo – is an important step in the right direction.
