Unearthing the Differences Between Cast Stone and Natural Limestone

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Designers, architects and homeowners alike want to create the most luxurious look possible for their building projects while feeling good knowing they’ve received the greatest value for their investment.

Those wanting to add the beauty of natural limestone will sometimes consider cast stone as an alternative, as they believe it can provide a similar appearance. Cast stone  — a man-made material similar to concrete — has been a common building material for more than a century in the U.S., and some consider it an economical alternative to natural stone. But often time reveals several significant drawbacks of the man-made building stone, and it’s important for those considering its application to be fully informed about appropriate uses and shortcomings.

Cast Stone Uses

People in the construction trade specify the use of cast stone for many applications, from something as simple as a decorative entryway for a home to larger treatments, such as a simulated cut stone veneer exterior for a commercial building or walkway.

Some use of cast stone is acceptable and may serve a similar function as natural limestone. However, cast stone should be avoided in:

  • Applications requiring structural support
  • Areas prone to chemical exposure
  • Exterior uses subjected to extreme temperature fluctuations
  • Expanses where water absorption is likely
  • Areas requiring minimal maintenance
  • Applications where custom chiseling or cutting is necessary

When cast stone is used inappropriately in building applications, the need to maintain, repair or replace damaged materials is often disruptive and costly, so make sure you’ve considered the conditions and elements it will be exposed to.

Natural limestone is extremely durable and can withstand the environmental conditions and load-bearing requirements that are commonly encountered in construction projects.

Unfavorable Attributes of Cast Stone

As with any man-made product, the quality of cast stone can vary greatly among manufacturers. The density and durability of the finished product will be dependent on the types of aggregates used, mixing methods, curing time and the consistency (or lack thereof) among various workers in the manufacturing facility.

All these variables can contribute to serious and potentially dangerous issues for building owners down the road. Consider the problems that commonly occur in cast stone applications:

Cracking

Unlike certain grades of its natural counterpart, cast stone is highly porous. For external applications, such as a building’s facade or pavers, this inevitably exposes the material to inclement weather and eventual water absorption. When water penetrates a material — especially in climates where freezing temperatures are common — expansion and contraction will cause cracking. In addition to an unattractive appearance, this can cause tripping hazards when used in high traffic floor areas.

Steel can be used to reinforce cast stone, but if water penetrates the surface and comes in contact with the steel, rust will develop and compromise the integrity of the material in addition to causing unsightly stains.

Crazing

Crazing, a pattern of hairline cracks resembling a checkerboard, is another issue commonly associated with cast stone. This is the result of moisture absorption and can precede cracking. Improper installation and applications can increase the likelihood of this defect, which is often considered an inevitable consequence of using cast stone. While it doesn’t always lead to structural concerns, the defect is unattractive, and the cracks can accumulate dirt and grime over time. If not addressed, these cracks can progress and form deeper channeling that leads to instability.

Chipping

The same conditions that lead to cracking and crazing can also result in chips and flaking. The dyes and finishes used in most man-made stone products do not penetrate to the interior, or there may be variations and streaking within that occur as part of the mixing process at the manufacturing plant. If the edge of a cast stone surface becomes marred or chipped, the underlying substrate becomes exposed and highly noticeable.

Staining

The porosity of cast stone allows stains to penetrate deeply into its surface. In interior applications, this can occur as a result of spilled food, beverages, cosmetics and more. Staining is even more prevalent in exterior applications where exposure to debris from trees, soil, foot traffic, pollution, rusty metal patio furniture and more are commonplace. Cleaning is laborious and often ineffective, and the types of cleaner used will vary depending on the material makeup of the product and may result in pitting or further discoloration.

Unsightly Repairs

Because cast stone is manufactured in lots, and because the artificial dyes used can fade over time, obtaining a matching piece to make repairs is difficult. Blending the repair without becoming evident is highly improbable, and the cost to replace a large expanse to avoid detection is prohibitive.

Limestone — The Natural Choice

Issues that consistently plague cast stone are of little consideration when using natural limestone, and limestone’s long-term investment value far exceeds its man-made counterpart. As it has for millions of years, natural limestone continues to demonstrate superior strength, durability and ability to withstand water absorption, and its low porosity makes it ideal in any climate. The beauty of limestone is unsurpassed, and the naturally occurring color variations and hues lend themselves to both highly refined, upscale applications or more rustic appearances.

Just as there are different qualities of cast stone, natural limestone differ based on where the stone is harvested. Limestone materials are rated based on several factors including strength, abrasion resistance, absorption and more. For the highest quality that can stand up to the most challenging man-made or environmental abuses, look for Type III limestone, which is far superior to less dense and stain-prone Type II or Type I materials.

To assure the best look and lasting value, be sure to request material samples and understand where natural limestone is best suited. Contact us to discuss the versatile options and applications for your next project.

Glossary of Stone Industry Terms

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