Natural Stone Ordering 101

By Matthew Doyle, Assistant Editor

The size of individual pieces also makes a difference in thickness according to Cunningham. A theoretical example he pointed out is that 1.25 inch thick pieces of 24×36 inch dimensional stone could handle pedestrian traffic, yet the same thickness would be plausible for forklift traffic in 4×4 inch pavers. Note that heavy vehicular traffic applications require at least a four-inch reinforced concrete bed according to the same source. Image Courtesy Krukowski Stone Company, Inc.

Natural stone hardscapes can be exceptionally beautiful, but as 20-year veteran Mark Vance of M.A.Vance Enterprises tells customers, it’s what you don’t see that matters. This mantra must be applied to the whole process, from ordering to installation for a successful natural stone paving project.

What stone should I purchase? How thick should I order it? How do I best store it? Most of these questions have complex answers that vary job-to-job, city-to-city and stone-to-stone. So the first step is finding an experienced supplier with a track record of satisfied landscape contractors knowledgeable in the local market to buy from. Working with the owner or an architectural representative will allow you to access years of additional experience in guiding your purchasing decisions.

Environmental factors are a major consideration in what type of stone to order. Natural stones with high absorbency rates are a concern around water features, particularly salt-water pools, as freeze-thaw cycles or salt crystallization can create spalding or delamination. Bare feet also present unique concerns poolside, with the aforementioned spalding or delamination creating cut hazards. Excessive solar absorption can also be uncomfortably warm on feet.

Selecting Thickness

A variety of mutually dependent factors are involved in determining the thickness needed, starting with your expected traffic. Is it commercial or residential? Obviously the former must stand up to far greater abuse. Will pedestrian or vehicular traffic be expected, or both? The greater weight of vehicles will normally demand a thicker cut of a given stone.

A final thickness consideration, particularly in dimensional stone, is the size of individual pavers. According to Cunningham, the larger the format and the heavier the anticipated traffic, the thicker the stone will need to be. In other words, a natural stone piece with smaller dimensions can handle heavier traffic than a piece with larger dimensions of the same thickness.

Determining the thickness needed for a given natural stone project involves many factors, but a major one is expected traffic. This residential walkway installation takes a far lighter beating than a commercial driveway installation, so the stone can be thinner. An architectural representative of your experienced supplier can usually tell you how much thinner. Images Courtesy Krukowski Stone Company, Inc.

Selecting Stone Type

Two crucial factors in natural stone selection are durability and aesthetics. Durability involves several considerations.

Another concern is the hardness of the rock, as softer stones can present a scratch risk.

…as 20-year veteran Mark Vance of M.A.Vance Enterprises tells customers, it’s what you don’t see that matters.”

Sealants

The sealant applied is a huge factor in durability. According to Key, sealers featuring fluorochemicals preserve breathability while establishing a strong seal. The breathability is important based on a problem Key dealt with in Hawaii. Marble had been placed indoors and topically sealed with a product similar to acrylic or vinyl acetate. As a result, the stone began cracking and peeling in layers. He claims to have seen similar problems elsewhere.

Bear in mind the best sealer cannot do its job improperly applied. Cunningham recommends coating stone thickly enough to remain wet for 30 minutes. He also points out that pool copings need extra attention, as gravity is fighting your best efforts on the high-abrasion area.

Soil composition is another key factor in determining thickness according to Steve Key of LLave International and K&M Trade Co. Aspects of the material type, such as clay or silt content in soils, will determine the base required to prevent settling. This in turn will establish how much support the natural stone will get against load. Note that local differences effect the proper thickness for otherwise identical projects.

Aesthetics

These factors are very hard to quantify and vary from city to city. For instance, Key claimed a stone is widely used in Florida pool surrounds for a very popular chipped and spalded appearance. The same decay would probably be scorned in other parts of the country.

However, if installing an aesthetically pleasing but questionably durable stone with the expectation that sealant and maintenance will overcome this shortcoming, make this reality VERY clear to the customer. As 15-year industry veteran Joanie Krukowski-Whitt noted, there are very real legal liability risks here. Also, remember that consulting a trusted supplier can help the contractor gauge the razor-fine line between success and failure in these situations.

Another key in determining thickness is what the base is constructed of, concrete (wet lay) or sand (dry lay). Concrete allows thinner stone according to Frank Cunningham of World Wide Stone, but is more expensive. Joanie Krukowski-Whitt, a 15-year industry veteran with Krukowski Stone Company, Inc., noted concrete was selected for the depicted installation for its durability and resistance to freeze-thaw damage.

Storage

Now that you’ve selected your natural stone, where do you put it before installation? There are three major concerns here, security, convenience and climate.

Paul Swencki of Cleveland Quarries, with 28 years in the industry, recommends https://www.buildingstoneinstitute.org/ and https://alliedstone.com/ for finding quality quarries and other information. Manufacturer sites with more information include https://durangostone.com/ and https://llaveinternational.com/index.html.