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Adding a natural stone design element to a building or landscape project creates a look of sophistication and quality that’s difficult to achieve with other materials. In an effort to cut up-front costs, some designers and builders consider using cast stone for pool coping and outdoor pavers — a man-made material that can mimic the appearance of natural stone and can seem to have similar characteristics at first glance. A closer look, however, often exposes limitations and long-term problems.
While many manufacturers of the man-made version have used the term “stone” in their marketing efforts, the reality is that cast stone is more closely related to concrete and has similar attributes...and drawbacks when stacked up against its natural counterpart.
Let’s compare the pros and cons of each in four major areas to help make a distinction between the two when used for pool coping and paver applications.
1. Material Composition
Man-made stone is produced using a variety of composite materials including aggregates, silicon, Portland cement, sand, pigments and a host of chemicals. Various processes are used during manufacturing to create cast stone, and inconsistencies in quality can occur during the manufacturing process as a result of improper curing, humidity, and even variances between different operators. Its surface is less dense and typically highly porous, making it prone to damage easily, especially in high-traffic or moisture-prone areas.
Natural limestone is quarried from sedimentary deposits formed over millions of years. Free of composites such as chemicals, aggregates and dyes, it’s less likely to chip, break and stain. If damage does occur, it’s usually less noticeable because the natural color is consistent from the surface to its core, whereas a damaged cast material can appear chalky and may expose interior color variances.
As with cast stone, there are different qualities of material available. Quality is determined in part by its classification by the American Society of Testing and Materials (ASTM), with Type III limestone receiving the highest ranking based on absorption, density, strength, abrasion resistance and more. As expected, Types I and II limestone receive lower scores and should be limited to fewer applications.
2. Visual Appeal
Since cast stone can be manufactured in a variety of colors not found in nature, it may be suited to some designers’ specifications. If a designer wants custom colors, however, the costs may be prohibitive. The standard molding process of pre-cast stone results in limited color options, sizes and predictable patterns that can be detected, especially when spread across an expanse where pavers are installed. If the look of a continuous coping around a pool without any seams is desired, cast stone can be used. However, the greater the expanse without seams, the greater likelihood the product will crack over time.
The natural tones, hues and variances in limestone add a charm unattainable with man-made products, and there are no artificial colors to fade over time. The patterns of limestone can differ depending on where it is quarried, and each piece will have subtle variations that can be appreciated for its unique beauty. The ability to cut natural stone into various custom sizes and shapes makes it ideal for arranging countless creative patterns. Natural stone will increase in beauty over time and can form an attractive patina, whereas man-made materials deteriorate over time.
3. Initial and Long-term Costs
The up-front cost is where cast stone can seem to have the upper hand. The initial investment is sometimes lower, which is why some contractors whose main goal is to undercut their competition and “win the bid” will spec cast stone instead of natural limestone. Custom applications, however, will often be comparable in cost to that of natural stone. When considering the long-term investment, the costs for man-made products can actually be higher than natural stone due to increased maintenance, repairs and shorter lifespans. Future investments will be required with cast stone and will result in greater costs over time.
Many people have a preconceived idea that natural stone is always more costly; however, there are many cost-effective solutions available, and newer technology and equipment have helped make it more affordable in today’s marketplace. When considering the long-term investment of stone products, natural stone wins out. It’s considered a permanent structure, and its lifespan far exceeds that of concrete-like products. Limestone requires relatively low maintenance and adds greater value to a property than cast stone every time, meaning resale values are higher, too.
4. Durability and Long-term Maintenance
A major consideration when choosing materials around a pool area is their ability to withstand the effects of water and the chemicals often associated with maintenance and upkeep. The composition of man-made stone typically results in a greater likelihood of water absorption. When water infiltrates the material, cracks and crazing can appear over time and mar its appearance, especially in northern climates with freeze/thaw cycles.
Chemicals can quickly deteriorate manufactured stone, leaving it pitted and discolored, which is why many experts don’t recommend its use around pools. Concrete also requires frequent deep cleaning to keep mold and mildew from forming on its highly porous surface. Costly crack repairs and resurfacing also will be required.
An occasional cleaning is required to remove debris and prevent dirt or algae but, in general, its appearance will increase in beauty from year to year. Natural stone has been subjected to environmental abuses for millenniums, so its ability to withstand the effects of water absorption are superior. This is especially critical when used as an exterior material as pavers or as pool coping where constant exposure to moisture is unavoidable. Type III dolomitic limestone is highly freeze/thaw and corrosion resistant.
We think you’ll agree that when weighing the overall pros and cons of cast stone versus limestone, the natural option is clearly the better investment and will add the most beauty and value to your project.