by Pennie Sabel

It has been used for thousands of years to build castles, temples, bories, brochs and trullis throughout Europe, Africa, Asia and the Americas. Terraces, canals, lighthouses, bridges, barns and walls stand today as they were built hundreds and thousands of years ago because of the durability and flexibility of the material and the skilled craftsmen and masons who labored on the construction.

The material is rubble stone, irregularly shaped stones skillfully pieced together by masons who build the jigsaw puzzle of tons of rock into beautiful, natural, living environments indoors and out. Contemporary applications include interior and exterior veneers in a variety of patterns, structural and decorative walls both mortared and dry stack, fireplaces and mantles, stair treads and walkways, patios and water features, signs and bridges. The stone itself can be granite, quartzite, limestone, sandstone, travertine, moss rock, fieldstone, or other locally available stones.

Quarrying operations for rubble stone vary according to the deposit. Some are quite simple and basic, others more technologically sophisticated. The stone is quarried using an excavating method that separates the usable stone from sub-soil and overburden. In sedimentary deposits, the stone is lifted out layer by layer with a front end loader. In areas where there are natural rockslides, stones are hand picked. As quarries deepen, air hammers and/or explosives are used to loosen the stone for processing.

Once removed from the quarry bed or deposit, the stones are further sorted, shaped and processed. Large blocks are cut into thick slabs by drilling holes, inserting "feathers" into the holes, and placing wedges between the feathers. Wedges are hammered until the slab separates from the block. Hydraulic splitters — or guillotines — break the slabs into specified size pieces. Much of the process, though, is labor intensive, hand splitting and shaping the stone using hammers, mauls, wedges and chisels.

The installation of rubble stone varies with the application. Wall veneer, landscape stone, walkways, free-standing or retaining walls all have their own unique installation challenges. All of the stone pieces must interlock and when there isn't just that right piece, it must be shaped on-site with splitters and hammers. And it all must meet the requirements of the owner, architect and builder.

Veneer products are installed using a mortar bed between the stones and the same concepts apply to both interior and exterior installations but with differences in the backing material. Veneer patterns can be random shaped mosaic, rough square or rectilinear, or horizontal ashlar. A mortar mix of Portland cement, lime, sand and potable water is used to knit the stone together as the wall is constructed. On walls over three feet in height, the stone is anchored or tied to the backing wall using metal anchors. The basic building blocks of a veneer installation are the "jumper" or larger stones that, according to Steve Schulte of Leonard Masonry in St. Louis, Missouri, should be arranged in roughly a diamond pattern. Built on the jumper are two smaller stones that, together, equal the jumper less the width of the mortar joint. For example, if the jumper is 15 inches and the two smaller stones are nine inches and four inches, then the mortar joint will be one inch. These units are then used to continue building the veneer wall. Schulte says that the goal is to have the mortar joint look even throughout the course. But it should not be too perfect; the jumpers should blend in and not look obvious.

Schulte says that there is a lot of math involved in determining the size and placement of the mortar joints and that is a slow and tedious process. Masons doing the installation work are truly masters of gigantic jigsaw puzzles.

Landscaping installations are a whole other story and are determined by the size of the area, the slope and drainage of the land, water features that may be man-made or natural, and the type of stone being used. Boulder installations require different techniques than flagstone paving and rip rap, flat stones installed to control erosion on the banks of rivers and streams, require yet another set of techniques.

The bottom line for rubble stone installations is what works in a particular environment and what looks best to showcase the area being landscaped. But where it goes and how it's put there is only part of the rubble stone story.

All segments of the natural stone industry are responding in one way or another to competition from manufactured products. And rubble stone is no exception. Promotional efforts at Champlain Stone in Warrensburg, New York, focus on the value of natural stone over manufactured products where maintenance is concerned. "Natural stone veneer is virtually maintenance free," says Champlain Stone's Jane Bennett, "and natural stone can be cut, chipped, split or sawed to reveal more stone. This is a benefit to the use of natural stone veneer, aiding in the creativity and flexibility of design and installation."

Thinner, lighter weight natural stone veneer is another counter to manufactured products. Rubble stone sawed thin on commercial sawing equipment can weigh in well under the 15 lbs. per square foot vertical load requirement, according to Bennett. She maintains that thin sawn rubble is changing the way consumers think about natural stone.

Woody Mercer of Cumberland Mountain Stone in Crossville, Tennessee, sees a recent trend to tumbled stone. "Tumbling the stone gives it a softer appearance by rounding the edges and giving it a cobble stone appearance," he said.

	A massive fireplace with sandstone inset at Grand Timber Lodge.

There is an ever increasing demand for natural indoor and outdoor environments for both residential and commercial projects, according to Matt Mueller of Siloam Stone in Canon City, Colorado. "Due to the increasing concerns about the environment and the unsightly development of our concrete metropolitan areas, natural is definitely in. If we want to create a natural environment, natural stone is, indeed,, the natural choice."

Natural environments, of course, lend themselves to earth tones — tans, browns, greys with accents of the more dramatic reds, rusts and greens — and that is what is most popular throughout the country when consumers and builders select natural rubble stone products for their projects. They blend well with other building materials and the surrounding environment whether it is in a natural setting or a metropolitan area, according to Woody Mercer.

David Little of Gallegos Corporation in Vail, Colorado, concurs with the trends toward more natural environments and earth tone colors in building projects. In his area, locally quarried moss rocks and stone from Telluride and Oklahoma are currently the most specified materials. Gaining in popularity are stones from Montana and limestones from Kansas and Texas.

The stone veneer at Grand Timber Lodge gives the restaurant entrance an old European feel.

Traditional styles are the most popular in the market served by Rolling Rock Building Stone in Boyertown, Pennsylvania. Horizontal lines, a more structural look, ashlar and square-rectangular shapes are in demand and limestones and sandstones are popular, according to Terrence Meck. "The use of natural stone in adhered veneer is something that we have been promoting for 15 years, and it currently is the largest growth segment of our business," he said.

These companies are all optimistic about the growth of the market for natural rubble stone applications. Mercer says, "stone is becoming more popular as a building material and more funds are being allocated on projects for landscaping which leads to the use of additional stone products."

Siloam Stone is seeing increases of 20 percent to 50 percent and doesn't anticipate a decline. But Mueller cautions that concern for the environment can be a double edge sword. "People love creating a beautiful environment, but they don't like the process", he said. Quarry operations are under scrutiny by environmentalists and obtaining new permits for natural stone quarries is becoming more difficult, The market could be drastically affected if permits for mining expansion are curtailed and the natural resource becomes more scarce.

Poolside at the Grand Timber Lodge in Breckenridge Colorado.

Champlain's Bennett looks at market growth from a promotional as well as environmental perspective. She sees more advertising and educational programs by stone suppliers to compete with manufactured stone producers will increase consumer awareness about the real benefits and values of natural stone. She sees the "Green Movement" in urban development as also something to consider in the use of natural stone. Natural stone is considered a "green" building material in that it is not a manufactured product. There are no pollutants emitted in the creation of natural stone. Unlike natural stone, manufactured products require the use of chemicals in their creation and they consume large amounts of energy in their manufacturing process. She says, "Natural rubble stone produces no off-gassing if buried or burned. It is a natural connection from the earth to us."

By the way, if you're puzzling over brochs, bories and trullis — brochs are circular dry stone towers found in Scotland; bories are dry stone huts, roughly like an igloo, found in the Provence region of southern France; and trullis are round dry stone structures with cone-shaped roofs found in the Apulia region of southern Italy, some of which are still in use today (restored, of course) as dwellings and rental properties for tourists.

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