Old-world masonry appeal – engineering & cost advantages
Natural stone is a timeless material that has been used for centuries in structures of all types. In one of the fastest growing segments of the masonry products market, adhered stone veneers have become increasingly popular during the past decade in both commercial and residential construction. The slim profiles afford builders, architects and designers with new options for interior and exterior wall design, both in remodeling and new construction. Compared with full-dimension stone, natural thin veneers offer substantial benefits, particularly in terms of engineering, shipping and installation.
A thin veneer is any lightweight, thin surface material that can be applied directly to a solid facing. In contrast to full-dimension stone masonry, which ranges upwards of four inches in depth, natural thin stone veneer averages in thickness from 3/4-inch to 1-1/4 inches, and must weigh 15 pounds or less per square foot as mandated by the Uniform Building Code (UBC). The elimination of a load-bearing foundation requirement equates to less engineering costs because of the reduction of structural reinforcements required. Thin stone veneer is ideal for areas that cannot support a heavy load, and it is a viable alternative for projects with limited space. Typically, thin veneer is sold in flat and corner pieces to provide flexibility in design and authenticity in aesthetics, as the product may be wrapped around a column or wall, providing a look similar to full-dimension stone.
Quarried from the earth
Natural thin stone veneer is quarried from the earth. The fabrication process has advanced technologically in the last few years by incorporating diamond saws and computers into the process. The best manufacturers also test thin veneers for freeze/thaw for use in all climates across the United States, in addition to adhering to strict specifications to ensure a consistent final product.
Because it is a natural product, the unique color of natural thin stone virtually eliminates the potential for repeating patterns on large projects. The other important quality of natural stone compared with the manufactured variety is that natural stone veneer is colorfast and will not fade over time. If it is cut to fit during the installation process, all you’ll see is stone inside, unlike manufactured stone, where the aggregate will be exposed under the same circumstances.
Natural thin stone veneer is durable with very little water absorption, eliminating the tendency to show efflorescence, which is a white, powdery deposit that can appear on the face of masonry walls. Natural stone veneer also is shown to outperform the manufactured alternative in several parameters, including compressive strength and freeze/thaw durability. Comparative data indicate that manufactured stone absorbs significantly more water per unit of weight than natural stone, and natural stone expands more over time, while manufactured stone tends to shrink because of drying and carbonation.
Styles of natural stone thin veneer
Natural thin stone veneer is available in a wide variety of styles and colors. The most prevalent shapes on the market include fieldstone, ashlar, and ledge stone. Fieldstone is characterized by irregular shapes set in a random pattern. Ashlar styles are composed of larger, rectangular pieces with square edges and flat surfaces. Ledge stone typically consists of longer pieces of stone with varying heights and depths. Blending or mixing several types of stone together can achieve a distinctive look. Natural thin veneer also can be trimmed during the installation process to obtain precise detailing objectives.
Cost savings implications
Since natural thin stone veneer is considered an applied veneer as outlined by the UBC mandate of weighing 15 pounds or less per square foot, there are several areas where the cost of the structure can be reduced. By eliminating the brick ledge, which is required for full-dimension stone, there will be less engineering involved, affording cost savings during the design process. The elimination of the brick ledge also will result in a savings because of less concrete and rebar being utilized during construction. In addition to engineering and construction cost savings, there are other cost savings advantages to using a lighter weight of thin veneer product in building, including ease of installation and reduction in transportation costs.
Natural thin stone veneer is easier to install than its full veneer or full-dimension masonry counterparts, and it installs using the same methods as manufactured veneer. A mason can haul and install far more material on an hourly and daily basis when using thin veneer. A crew can lay an average of 125 feet of thin veneer per day compared with just 40 to 60 feet of full veneer. This variance affords a significant opportunity to increase labor efficiencies; since faster installation means the same crew can take on more jobs in the same period of time.
With rising fuel prices being felt across the nation, transportation costs are an increasingly important variable in specifying building materials. Because of its smaller size and weight, more thin veneer can be shipped per truckload. For example, a truck traveling from Denver to Atlanta can haul enough full-depth stone (typically four inches deep) to cover 1,000 square feet of wall surface, or enough thin stone veneer to cover 4,000 square feet. Generally, that translates to a reduction in transportation costs by a factor of four.
|Natural and Manufactured Stone Property Comparison|
by Weight2, %
|Shrinkage (—) and|
|1,800 to 20,000|
|0.2 to 12|
13 to 29
|0.0264 to 0.0804|
0.0432 to 0.0744
|(+) 0.00048 to 0.012|
(—) 0.054 to 0.084
|Table courtesy of the Rocky Mountain Masonry Institute.
Thin stone veneer typically comes packaged in large boxes that contain approximately 100 square feet of flats or approximately 100 linear feet of corners, and small boxes that contain five square feet of flats or five linear feet of corners. Products are packaged under the assumption that a 1/2-inch mortar joint will be used in installation. Dry stacking the materials will require about 30 percent more product.
The amount of thin veneer material needed for a project can be calculated using the following method:
- Multiply the width by the height of areas to be covered (total square footage).
- Estimate corners required by measuring the total height of the wall corners to be covered. This will equal the number of linear feet of thin veneer corners needed.
- Subtract 75 percent of the corner linear foot calculation from the total square feet to be covered. This will equal the number of square feet of flat pieces of veneer needed.
Because it is natural, thin stone veneers support a broad range of sustainability and energy-efficiency goals. Natural stone is highly durable, non-toxic and easy to clean. Like brick, stone has good ”thermal mass,” defined as a material’s ability to store heat and then slowly release it, thereby keeping extremes of exterior temperatures from affecting ambient temperatures indoors. Natural stone has some of the mass of its full-dimension equivalents and does offer partial thermal, sound and fire-resistance qualities.
With a life span of more than 1,000 years when properly designed and built, natural thin stone veneer provides longevity to homes and buildings. Unused materials may be salvaged and used in another structure, or recycled for such uses as roadway sub-base materials or permanent landscaping.
Thin stone veneer that is properly adhered to the substrate will last a lifetime. Generally, failure of thin stone veneer in the field is the result of poor installation. It is important to follow set building codes established for thin veneer materials, which provide guidelines for the inclusion of weather-resistant barriers, metal lath, fastener, and joint information. The following codes should be consulted:
- 2006 International Building Code (IBC) (Section 1405.9)
- 2006 International Residential Code (IRC) (Table R703.4 Note Z)
- 2005 Building Code Requirements for Masonry Structures, Masonry Standards Joint Committee Code, ACI-530-05/ASCE 5-05/TMS 402-05 (Sections 6.1 and 6.3)
- 1999 Standard Building Code (SBC)
- 1997 Uniform Building Code (UBC).
Building codes vary by region, and it is important to check local building codes, particularly in areas with frequent seismic activity.
Installation and design control
Thin stone veneer may be installed right out of the box, however, many masons prefer to lie out the product on the ground or floor to facilitate planning and to ensure an easier installation and design control. Mortar color selection will affect the overall product appearance as will mortar joint dimension or dry stacking the material, which eliminates the mortar joint. Selecting a qualified mason is key – an experienced one will be skilled at sawing stones into a coherent design that will ensure an aesthetically pleasing finished product.
Thin stone veneer may be applied directly over any clean masonry surface such as concrete block, brick or cement. The installation process is the same as synthetic stone, except a smooth-backed natural stone actually adheres better than the rough backs of synthetic stone because manufactured stone can absorb the moisture out of the mortar prior to curing, resulting in a weaker bond. In most exterior applications, a weather-resistant barrier should be used to cover the wall. However, thin veneer applied to masonry, stucco or block that is clean and untreated does not require a weather-resistant barrier or metal lath. According to the Rocky Mountain Masonry Institute, generally speaking, natural stone veneer applications are inherently weather-resistant. In areas that receive constant wetting, including walls and sills, water-repellent treatments will help the wall resist moisture penetration and staining.
Dry stacked applications are not recommended for exterior installation in climates with freeze/thaw weather cycles, but may be used for interior installations or warm climates where it does not freeze. Previously exposed surfaces that have been stained, sealed, painted, or treated should be sand blasted to insure proper mortar bond.
Thin stone veneer products are virtually maintenance free. All that is generally required is periodic washing with mild soap or detergent and a soft brush to remove surface dirt and dust. Wire brushes should never be used, nor should acid or acid-based products.
Properly designed and installed, thin stone veneers provide unique design possibilities to meet aesthetic and sustainability goals at an affordable price. There are a wide variety of styles and colors from which to chose, making the ability to provide natural, distinctive solutions to customers an affordable and beautiful reality.
Jim Hambleton is the national sales manager for Robinson Brick Company in Denver, Colo. He can be reached via e-mail at Jim.email@example.com.