Stone - The Advantages of Man-Made

A blend of manufactured stone was in keeping with the environmentally conscious spirit of Alabama's Little River Canyon Center. Photo courtesy of Eldorado Stone.

Stone has been used as a building material for thousands of years. Long recognized for its durability and artistic quality, stone has been the preferred choice for buildings of status and power through the ages. When it comes to stone as a building material, today's issue is: should it be natural or manufactured' Aren't all natural products preferable to the manufactured alternative? In the life cycle assessment of a product, the answer is more complex. "Manufactured stone is growing in popularity as an alternative to natural stone because of its believability, affordability and the sincere warmth and texture it can bring to any space indoors and out," says Brent Spann, VP of Marketing for Eldorado Stone. When you use natural stone, you can only use what's available and when that vein of stone color is gone, it's gone in nature."

An unwillingness to tap the reserves of natural stone was one factor in the decision to specify a manufactured alternative for a teaching center in the heart of a unspoiled wilderness area. The 25,000-squarefoot LEED-certified Little River Canyon Center is situated in the Little River Canyon National Preserve, one of the deepest, most extensive canyon and gorge systems east of the Mississippi; it has been designated as a "Natural Wonder" of ecological and scenic significance by the Alabama Environmental Council. When completed in 2009, the center will serve as the headquarters for the National Park system and as a field school for Jacksonville State University. A custom blend of 12,000 feet of manufactured stone was used around the base of the building, for columns, and even for the entry sign. "We chose the manufactured stone not only for the structural cost savings but because it didn't require further disruption of the landscape as quarrying real stone might have," says Jay Jenkins, AIA , Partner in JMJ Architecture in Anniston, Alabama. "We felt the manufactured stone was in keeping with the spirit of the center and what we were trying to accomplish, which was to protect and conserve natural resources. And you can't tell it isn't real stone."

Stone at Florida's Parkland Sports Club takes inspiration from France and Italy. Photo courtesy of Eldorado Stone.

The authenticity of manufactured stone, which is used for walls and vertical applications, is generally attributed to the fact that it is cast from highly detailed molds of real stone and that the base color is blended throughout and permanent mineral oxide pigments are applied and absorbed when the material is cast. Sealants are not required with this product. Some people prefer to have a sealant or like a polished stone look. If a sealant is used, a silicone or water-based sealant is recommended. "The authenticity and natural look of the stone is what will attract a customer," Spann says. "The ability to also create custom colors and blends by taking some stones from different profiles and mixing them gives architects the creative control they love. And a manufactured stone allows you to match up with existing stone even many years later. You have the assurance of getting what you need when you need it."

Most stone manufacturers warranty their products for 40 to 50 years and stand behind the warranty that they can match stone that hasn't experienced excessive fading. However, it's important for a customer to look at a manufacturer's overall track record when it comes to performance data and product durability.

Getting what you want when you need it constitutes a savings in the cost and transportation requirements for architects charged with creating a look inspired by another era or country. Don Gregory, AIA , and his team at JZMK Partners in Parkland, Florida, selected manufactured stone with an overgrout technique in their design of a 54,000-sq. ft. Sports Club. "Our extensive use of stone was done to replicate the indigenous-styled stones of what you would find in France, Italy and Tuscany," says Gregory. "We were very particular about the color, shape and style of the stone as well as the grout technique used. We wanted the grout to appear as if it had been scraped off with a stick so it would reinforce our efforts to capture the look of old-style construction."

Driven by consumers' desire for stone with regional authenticity, manufacturers are responding with research and development to produce new stone profiles that mimic the natural stone of a particular region. Adobe bricks for the Southwest market, lava stone for the Hawaiian Islands and western U.S., and coral stone for Florida and other coastal states are examples of this effort.

There are other reasons too that make manufactured stone preferable in some instances to real stone. Manufactured stones range in thickness from 1 inch to 2.5 inches on average depending on the profile and is about one-third the weight of real stone, meaning it can be adhered directly to a substrate, and is cost effective to transport and install.

Manufacturers say that simulated stone is able to be used in all weather conditions, with the exception that it should not be installed in a fountain environment. In exterior installations, a rigid, corrosion-resistant flashing - and a means of drainage - should be installed at all penetrations and terminations of the veneer cladding. Flashing type and locations shall be in accordance with the requirements of the applicable code.

Current codes recommend that the installation of the stone terminate at 4 inches above grade and 2 inches above a concrete walkway. Humidity is not an issue, nor is snow piling up against the stone. What is a concern is when the stone experiences several freeze-thaw cycles annually, such as in Reno, Nevada, which experiences 150 freeze-thaw cycles per year. Architects should confirm that products are designed, tested and manufactured to work well in freeze-thaw areas. This is based on quality control in the manufacturing process and sensitivity to air entrainment in the mix, meaning that air bubbles are intentionally included in the concrete to deal with any expansion issues.

One not-so-green feature is that a typical manufactured stone product might contain a high percentage of Portland cement, a material with high embodied energy. However, many manufacturers have significantly replaced the cement with content with recycled materials, such as fly ash, a byproduct of coal burning. Some manufacturers also give specifiers the option to add other types of recycled elements, like plastic bottles and glass to the stone. "The industry as a whole sees the value of finding simple ways to reduce, reuse and recycle in its manufacturing processes," says Spann. "And keep in mind that concrete itself is a recyclable product that is being used as an aggregate in new road, sidewalk and slab construction, so the life cycle story of manufactured stone is a good one."