Characteristics that the best facade stone should possess

Generally, there are two main types of natural stones commonly used for building facades: sedimentary stones (with a limestone base) and igneous stones (granite group). Limestone stones typically have their particular followers due to the veining visible in them, while granite stones, which were often utilized in modern buildings, are now seldom used in external facades due to their high weight, low water absorption, and lack of adhesion to the building structure.

The exterior facade of a building is particularly important because it is exposed to various weather conditions (rain, frost, sunlight, and pollutants). The best facade stone must have specific features to withstand these factors. It should possess unique characteristics such as durability, natural beauty, and thermal performance. It resists weathering, corrosion, and impact, making it a cost-effective (given its performance) and popular choice for any type of building facade. The natural beauty of the stone enhances the visual appeal of the structure, while its excellent thermal performance helps regulate internal temperatures and reduces energy consumption required for heating and cooling.

The best facade stone should be free from harmful minerals, as these can react with the elements and cause premature deterioration. The presence of impurities concentrated in a single spot or a line can be a weakness that may lead to the stone's degradation. Ultimately, when selecting the best facade stone, attention should be paid to its adhesion with the mortar and the likelihood of its detachment under various weather conditions and potential seismic activity.

Introduction to Types of Facade Stones and Parameters Affecting the Selection of the Best Facade Stone in Buildings

1. 
   Travertine

Travertine stone is considered one of the best-selling stones in the decorative stone market. This stone, which falls under the category of sedimentary rocks, is a type of porous limestone formed from the sedimentation and deposition of hot spring deposits. Travertine has a porous texture and comes in various colors and banded patterns. The color variation is due to differences in the compositions present during the sedimentation process, which manifest as different streaks. The fewer soluble elements in the water from these sources, the lighter the color of the stone will be.

One of the unique features of travertine that distinguishes it from other stones is its porous texture, which is created by the escape of gases during the formation of the stone. This characteristic not only gives the stone an attractive appearance but also provides significant technical advantages during installation. As mentioned, the best facade stone should not only be beautiful but also resistant to weather conditions, as well as to compressive and abrasive forces. It should also have good adhesion to the mortar, which reduces the risks associated with the potential falling of the stone. Travertine, with its mentioned properties and its porosity, is both lightweight and has good adhesion to mortar, which is considered a strong point for it.

Travertine stone, with its positive characteristics that the best facade stone can possess, deserves the saying that what all the good stones have, travertine has all in one. Important factors that have contributed to the increasing popularity of travertine today include the very high variety of travertine stones in different types and the numerous sorting options available for this stone. In Iran, travertine stones are primarily used for the exterior facade of buildings, as well as for Roman and classical styles. Additionally, travertine is recognized as one of the most suitable stones for flooring, being used in areas such as lobbies and even courtyards.

Other applications of travertine, especially light-colored travertine, include its use in the creation of sculptures, stone objects, and decorative items due to its workability. Constructing staircases is another application of travertine, which is feasible because of the stone's high polishability. Unpolished cream travertine is also suitable for use in bathrooms and pool floors. Travertine can also be used on kitchen walls. Its fire resistance makes it suitable for constructing fire pits as well. The use of this stone in fireplaces, house entrances, and hallway floors is also common.

Among the best cream and silver travertines in Iran are the cream travertine from Abarkouh and the silver and cream travertine from Takab. Additionally, the red travertine from Azarshahr is a well-known area in Iran that has beautiful red travertines. In terms of design and application, the red travertines from Azarshahr are of higher quality compared to other samples available in the market. This stone also has many fans in other countries, with a significant portion of it being exported to various parts of the world each year.

Globally, travertine stones have been used in the facades of important buildings, and some examples include:

1. The Colosseum in Rome, Italy: This ancient Roman amphitheater is made from travertine stone extracted from Tivoli, Italy. The color of the travertine used in the Colosseum is a natural beige cream.
2. The Getty Center in Los Angeles, USA: The beautiful architecture of this museum is constructed from travertine sourced from Bagni di Tivoli, Italy. The color of the travertine used at the Getty Center is light cream with fine streaks.
3. The Sacré-Coeur Basilica in Paris, France: The Sacré-Coeur Basilica uses travertine stone extracted from quarries near Paris, France. The color of the travertine used in the Sacré-Coeur is a soft ivory with hints of pink.
4. The Palace of Versailles in Versailles, France: A symbol of absolute monarchy from ancient times, its facade includes travertine.
5. Porcelain Stone (Crystal)

Porcelain stone, also known as crystal, is a type of metamorphic limestone that has been re-crystallized under high pressure and temperature. This type of stone can often be found in a range of colors from white to milky, and some varieties also exhibit gray and golden streaks. In addition to its use in the interior or exterior facades of buildings, Porcelain stone is widely used in the creation of decorative items and sculptures.

One of the most important features that distinguishes Porcelain stone from other stones is its ability to allow light to pass through. Due to its crystalline structure, it bears a strong resemblance to marble, which is why it has been named crystal. This property enhances the beauty of the stone, allowing for the creation of decorative elements in interior spaces and combining it with attractive lighting.

The installation of crystal stone, especially Bianco Crystal and Laibid, which are among the best examples of crystal stone in Iran, is done in book-matched and four-matched patterns on the walls of reception areas and hotel halls, accompanied by backlighting, adding a special beauty and charm to the space.

Porcelainstone is very strong and durable, with high compressive and abrasive resistance. Therefore, it is always a suitable option for flooring in industrial, educational, commercial, and office environments. The high density and compactness of Porcelain stone result in very low water absorption, preventing corrosion or wear. Additionally, this stone is highly resistant to detergents and acidic substances, making it easy to install in areas such as bathrooms and kitchens without worry.

Its resistance to weather conditions and its light color suggest that this stone is also suitable for use in exterior facades; however, the high density of the stone's structure and the lack of porosity can lead to poor adhesion to mortar. If we want to use this stone as a facade material, the strength of the facade may be compromised, which could be dangerous or lead to future costs. Nevertheless, by following certain guidelines, Porcelain stone can also be used in the exterior of buildings. For example, using a mesh behind the stone and increasing the adhesion of the crystal stone can enhance its safety and allow it to be installed as a facade stone.

The use of this facade stone is particularly popular in tropical regions because its light color does not absorb heat, keeping the building cool. Among the best examples of crystal stone in Iran are Bianco Crystal, Laibid Crystal, and Godar Sorkh, which have high demand in the construction stone market.

Here are some famous buildings that feature Porcelain stone in their facades:

1. The Louvre Pyramid in Paris, France: The Porcelain stone used in the Louvre Pyramid is called Bianco Carrara, a white stone with gray streaks.
2. The San Francisco Museum of Modern Art in the United States: The Porcelain stone used in the facade of the San Francisco Museum of Modern Art is known as Calacatta Gold, a white stone with golden and gray streaks.
3. The Museum of Islamic Art in Doha, Qatar: The Crystal stone used in the Museum of Islamic Art is called Imperial White, a white stone with soft gray streaks.
4. The Guggenheim Museum in Bilbao, Spain: The Crystal stone used is Statuario, a white stone with gray streaks.
5. The Sydney Opera House in Sydney, Australia: The Porcelain stone used is Calacatta Borghini, a white stone with golden and gray streaks.

 

 

1. Granite

As mentioned in the important considerations for selecting the best facade stone, a good facade stone should have high strength and be suitable for the climatic conditions of the area. Granite stones are among the most durable building stones; however, they are used less frequently for building facades for two main reasons. First, granite is relatively heavy and does not adhere well to mortar, which can lead to the stone detaching and falling from the facade, posing significant risks. The second issue is the oxidation of iron present in many varieties of this stone, which causes erosion and diminishes its beauty.

Despite the aforementioned problems with granite, its supporters have found solutions to mitigate these issues so that this beautiful stone can still be seen in various urban designs and facades. Advocates of granite consider its high durability and the variety of colors and patterns as one of its strengths, believing that with the use of skilled installers, granite can be one of the best stones for building facades and can last for many years.

In addition to interior and exterior facades, granite can be used for stairs, parking lots, floors, and walls of all types of buildings. It is also used for countertops, cabinets, and sinks in kitchens, for landscaping in urban and personal spaces, sidewalks, curbing, decorative and ornamental works, and more.

There are also famous buildings around the world that feature granite in their facades. Here are the details of each:

1. Empire State Building in New York City, USA: The granite used in the facade of the Empire State Building is sourced from the Adirondack Mountains in New York. The specific type of granite used is known as "Adirondack Red," recognized for its dark red color with black and white speckles.
   
   2. Taj Mahal in Agra, India: The granite used in the construction of the Taj Mahal is sourced from the state of Rajasthan in India. The specific type of granite used is called "Black Rajasthan," which is a dark black stone with white and gray veins.
2. 
   Sydney Opera House in Sydney, Australia: The granite used in the facade of the Sydney Opera House is extracted from the Tarana region in New South Wales, Australia. The specific type of granite used is referred to as "Tarana Blue," a blue-gray stone with subtle color variations.
   
   4. Royal Ontario Museum in Toronto, Canada: The granite used in the Royal Ontario Museum is sourced from the Canadian Shield, known for its unique combination of pink, gray, and black colors.
   
   5. Elbphilharmonie in Hamburg, Germany: The granite used is sourced from the Harz Mountains in Germany, recognized for its dark gray color with subtle variations.
   
   6. United States Capitol in Washington, D.C., USA: The venue for the United States Congress features a magnificent facade made of marble and granite.
3. 
   Montreal Olympic Stadium in Montreal, Canada: Known for its unique architecture, a significant amount of granite was used in its construction.
4. Marmarite (low grad marble)

Marmarite is actually a sedimentary limestone that differs from marble. Due to its characteristics, Marmarite is generally very suitable for indoor building applications and covered spaces. In fact, it is better to limit the use of Marmarite to interior facades. For example, its main applications should be for walls and floors of buildings, hallways, parking lots, restrooms, bathrooms, inside elevators, and so on. The stone has a high capacity for polishing and cutting, allowing it to be used in various designs and shapes. Overall, Marmarite is considered one of the most beautiful and diverse building stones, available in various colors. Some types of Marmarite are more expensive due to their notable features and advantages. For instance, Makia Black and Makia Gold marbleites are very beautiful and luxurious stones that are often used in the interiors of residential units and commercial and administrative centers, especially in luxury venues like hotels and banquet halls, due to their stunning white and golden veining on a black background.

Marmarite is sensitive to mechanical impacts and abrasion; it is, in fact, a soft and flexible stone. Therefore, it should not be used in environments with higher mechanical effects and wear, such as public places that experience heavy foot traffic, where stronger stones are required. Another issue is the very difficult installation of marbleite. Being a stone with a high degree of hardness, its installation requires expertise and the necessary equipment, which increases the costs associated with its installation.

Considering that the term "marble" is used in English for both marble and marbleite, and there is no separate term for marbleite, here are some important places where marble or Marmarite has been used in their facades:

1. 
   Parthenon in Athens, Greece: An ancient temple dedicated to the goddess Athena, made of Pentelic marble, which is a type of white marble with a subtle golden hue, extracted from the Penteli mountains near Athens.
2. 
   Taj Mahal in Agra, India: The Taj Mahal is constructed using Makrana marble, which is high-quality white marble with soft gray veining, sourced from the Makrana region in Rajasthan, India.
3. 
   Lincoln Memorial in Washington, D.C., United States: The Lincoln Memorial is made of Yule marble, which is pure white marble with fine grain, sourced from the Yule Creek Valley in Colorado, United States.
4. 
   Supreme Court of the United States in Washington, D.C.: This iconic building features a large facade made of white Vermont marble.
5. 
   St. Peter's Basilica in Vatican City: This Renaissance church is adorned with beautiful marbles in various colors in both its interior and exterior facades.
6. 
   Petronas Towers in Kuala Lumpur, Malaysia: The stone used is Nero Marquina, a black marble with white veining.