This course is part of the Natural Stone Academy

Special Considerations: Granite

Granite requires regular cleaning. Daily wiping with a mild, neutral cleaner should be adequate.

As with any stone surface, the use of cutting boards, trivets, and cooling racks can protect the material from stains. Paying attention to areas that are frequently exposed to water can help prevent the buildup of calcium and magnesium, which can leave a dull, whitish film on any surface.

Some varieties of granite may benefit from an impregnating sealer. However, application and maintenance frequency may depend on stone variety and use, so it is important to consult the sealer manufacturer for specific product recommendations. Some may not need sealing at all or will only require one application. Others may require several applications to properly seal them. Penetrating sealers should be used for surfaces that see heavy use or are exposed to water on a daily basis, such as bathroom and kitchen counters. A sealer can last up to 10 years; however, inappropriate cleaning products can compromise the sealer.

Natural Stone and Sustainability

Natural stone is naturally sustainable. It has been used for millennia, often requiring minimal processing. Natural stone is not bonded together with petroleum-based resins, nor is it created in a factory. Stone is durable, will not need replacing, and requires little maintenance. The material does not emit harmful chemicals and is 100 percent recyclable.

Because of these characteristics, natural stone has a favorable life-cycle environmental impact when compared with other building materials, especially when sourced locally. In addition, a sustainability standard developed for the natural stone industry ensures the sustainability of certified stone products, from cradle to gate. By working with a quarry that has implemented socially and environmentally responsible practices, including a plan for reclamation, you can feel confident that you are specifying a product with a good environmental pedigree. Natural stone products can also contribute to green building certification.

An Enduring Life Cycle

The best evidence for the durability of natural stone lies in the many iconic buildings that still stand centuries after they were built. In contemporary architecture, there is a trend to “build for the future,” with an understanding that a “green” building is one that will stand the test of time. Materials and products with a longer life cycle can help contribute to the longevity of these buildings and reduce the embodied energy and energy associated with replacing them.

Whether the application is a stone floor, countertop, or wall cladding, natural stone should last for at least 100 years or longer. When the building is finally demolished and/or the stone product removed, it is easily recyclable. In fact, nearly 100 percent of stone from deconstructed projects is recyclable and may be recovered for use in new buildings, or crushed for use in roadbeds and other infrastructure.

Embodied energy tallies the energy consumed by all the processes associated with the production of a building, including mining and processing of natural resources, manufacturing, transport, and product delivery. The embodied energy of a building material can be equivalent to many years of operational energy.

Natural stone is nearly complete as a building material in its natural state; it has one of the lowest embodied energy values of any comparable building material.

Once extracted, natural stone requires minimal processing or fabrication. Consequently, the energy associated with quarrying and preparing stone for market is quite low compared to many other materials used in similar applications—for example, ceramic tile, carpet, and vinyl flooring.

A German study that compared the life-cycle impacts of several floor coverings showed that natural stone has the lowest global-warming potential (GWP) of all of them. According to the study, which used environmental product declarations (EPDs) provided by manufacturers to compare impacts, the GWP of carpet was more than 20 times higher than that of natural stone tile.

Because stone is so durable, it does not need refurbishing or replacement. A stone floor, for example, will easily last 50 years or more and require little maintenance other than routine cleaning. In that same period, carpeting may need replacing up to four times.

It should be noted that transportation energy can be quite high for natural stone, as it is a dense (heavy) material. However, natural stone is a single-ingredient material. Other competing materials contain multiple ingredients, each of which require transportation to the manufacturing facility and contribute to the total environmental impact.

Consequently, sourcing stone products regionally can go a long way toward reducing the material’s environmental footprint. In addition, most green building rating systems incentivize the support of products and businesses that are close to the project site. Regionally manufactured and extracted materials reduce environmental impacts by reducing emissions of greenhouse gasses during transportation while supporting local economies. Fortunately, there are stone quarry sites within 500 miles of nearly every building site in the United States and Canada. Selecting reclaimed material is another good option that will extend the stone’s operational life and reduce the embodied energy of your project.

Health and Indoor Air Quality

Natural stone can support good indoor air quality. Because it is a natural material with few if any additives, it is easy to “vet” and unlikely to contain any harmful materials or chemicals, such as those included on the Living Building Challenge’s Red List. Be aware, however, that processing may add resin or cementitious fillers, fiberglass mesh backing, topical or penetrating sealers, or other chemicals; be sure to seek material transparency documents for these products.

Research conducted by the University of Tennessee's Center for Clean Products found that natural stone does not directly emit any volatile organic compounds (VOCs). Low- and no-VOC setting materials may be specified to ensure indoor air quality is not compromised. Natural stone also does not release harmful substances when exposed to fire, and the material is itself noncombustible.

Photos courtesy of Polycor

These photos from an active quarry show how much stone has been harvested over a 10-year period.