The Purity and Architectural Beauty of Marble Facades
Timeless, enduring, and stately, marble has been used since ancient Greece and Rome for the most important buildings of civilized society, from temples to bath houses to markets. The expense of quarrying and transporting the stone often constituted the bulk of construction costs, along with the workmanship of shaping and securing the heavy blocks. As the cost of labor increased, use of marble came to be reserved for the most socially significant buildings, such as courthouses and city halls. With technological advances in the last half-century, marble became available not only as traditional dimension stone, but as thin panel cladding.
Marble is a metamorphic rock that derives from the transformation of limestone and other sedimentary carbonate rocks under high heat and pressure. Unlike slate or mica, in which differential stress creates planes of cleavage, marble is non-foliated, which permits its widespread use in sculpture and construction. Hundreds of different types of marble are found throughout the world, including the United States, Europe, Egypt, and India. Characteristic veins and gradations in color result from impurities in the limestone, which move and re-crystallize as the stone metamorphoses into marble. In commercial applications, the term “marble” may refer to a number of geologic formulations, including true calcite and dolomite marbles, as well as travertine, serpentine, and hard limestone.
From the monumental ruins of antiquity to the lavish master baths of today, marble has had a rich and tumultuous history. Once the premier material in the architect’s palette, the difficulties of building with this luxurious stone and the development of cheaper alternatives have led to a steady decline in its use as a facade treatment.
Three of the most emblematic architects of the 20th Century –Adolf Loos, Mies van der Rohe and Philip Johnson– share not only their stylistic tastes and minimalist aesthetic, but also their passion for marble.
But who says you can’t teach an old dog new tricks? Employing state-of-the-art construction methods and inventive design strategies, these contemporary facades seek to restore marble to its former glory.
What makes it a firm candidate with respect to other construction materials? Let’s see it.
Available in a wide range of colors as well as polychrome inlaid with other minerals, it is appreciated because of its strength, durability and luxurious aesthetics.
The manufacturing tolerance on the thickness and face dimensions of stones is set out in BS 8298: 2000 and confirms to the European Standard BSEN 1469.
a) Units 50mm thick or less: the length and height dimensions should not vary from those specified by more than ± 2mm.
b) Units over 50mm thick: the length and height dimensions should not vary from those specified by more than ± 3mm in 900mm.
The objective is to achieve safe and reliable fixing of the cladding and full consideration at an early stage of the design work is essential. Fixings must be capable of three-dimensional adjustment to accommodate construction tolerances.
a) Dead Loads (Permanent) The actual weight of the supported stonework, which can be conservatively assessed using a density of 3 tones per cubic meter. In some cases the stone may be offset from the centre of support and the dead load will then act eccentrically on the fixings.
b) Applied Loads (Transient) Caused by wind pressure and section, window cleaning equipment, thermal and structural movements, etc. These loads will need to be assessed by a Structural Engineer.
Fixings must be produced from stainless steel or non-ferrous metal, must be of sufficient size and strength to resist the relevant forces and must be readily available to meet the construction programme.
Marble, sealant, concrete and steel respond differently to changes in temperature, wind pressure, and seismic forces. Unless facade design anticipates and responds to these varying degrees of change, the wall system will fail under the stress of restricted movement. To improve tolerance for this differential movement, a bond breaker, usually a polyethylene sheet or foam pad, may be installed between marble panels and concrete back-up. Likewise, accommodate movement at anchor points by drilling kerfs and holes slightly larger than the anchor. In the past, this anchorage space was often filled with epoxy to maintain water-tightness. However, epoxies restrict shear movement, which can cause the marble to crack. Instead, opt for rubber grommets or flexible sealants that balance the need for water protection with the requirement for movement tolerance.
Hysteresis increases the porosity of marble, permitting additional moisture to enter the panel. Damage to the marble from freeze/thaw cycling, salts, acid rain, and pollutants then occurs from the inside out, not just at the surface. Joint treatments are particularly critical in preventing moisture intrusion behind the panels, which can lead to heaving, displacement, and cracking. Water can also cause anchors to corrode. Not only does this compromise the strength of panel supports, the expansive forces of the deteriorating metal can crack the stone, creating further moisture entry points and accelerating the cycle of deterioration. Controlling moisture egress through the appropriate use of flashings and weep holes, which channel winddriven rain and condensation out of the wall system, are integral to the durability of the facade.
Rain water and rapid temperature changes can cause detail deterioration and surface erosion. As the surface of the marble deteriorates, bonds between mineral particles in the marble weaken, and the stone’s flexural strength, or ability to resist loads without deformation, can become compromised.
When people think of marble buildings, images come to mind of the ancient world. However, the material is still being used today to create jaw-dropping works of contemporary architecture, and this is happening from Canada to India.
Here are some of the best ways that marble has been used to breathe new life into the modern world.
Thanks for reading! 🙂
Originally published at www.tmd.studio on February 16, 2019.
The Purity and Architectural Beauty of Marble Facades
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