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When winter hits, colder climates are blanketed with snow and ice. Landscaping made beautiful with natural stone walkways during warmer weather are out of sight, out of mind for months — putting them at considerable risk for damage by melting agents containing varying degrees of salt, from sodium chloride to magnesium chloride.
It seems counterintuitive that salt can threaten one of the world’s most durable and low-maintenance substances, yet natural stone installed in landscapes is particularly vulnerable in three fundamental ways:
- Mortar degradation: Walkways comprised of brick, pavers, flagstone or some combination thereof are usually set in place using mortar, a thick mixture of water, sand and cement. A particularly snowy winter often means repeated scattering of salt over walkways, resulting in mortar erosion. When mortar pointing breaks down, the natural stone elements come loose. The result? A walking hazard for all seasons that requires costly removal and reconstruction to fix.
- Discoloration: The chloride in salt acts like a bleaching agent, leaching color out of natural stone surfaces. For example, salt pellets coming into contact with bluestone pavers will leave behind white “dots” or similar oxidized stains that can permanently flaw the natural beauty of the pavers.
- Deterioration: The harshness of salt can rapidly wear away certain less dense limestone, like Types I and II, and also delaminate veneers. Softer stone may make landscaping more susceptible to deterioration, whereas using granite or Type III Dolomitic Limestone — stone with the highest density quality and proven strength — will deter premature decline. In fact, commercial builders routinely use this harder stone to construct bases of building facades to ward off the erosive effects of salt spray from snow plows.
If you’re thinking your only options for preserving natural stone landscaping is either a shovel and some elbow grease or avoiding salt and other melting agents altogether, neither solution is always practical.
Instead, consider these alternatives to minimize the impact of salt on your landscaping for year round enjoyment of the natural stone you so carefully chose to beautify your surroundings:
- Calcium Magnesium Acetate (CMA): CMA is a natural, water soluble acid that is similar to vinegar in composition. Much gentler, more environmentally friendly and safer for pets and vegetation than salt-based melting agents, CMA is increasingly the deicer of choice for natural stone landscapes. A word of caution, however. Some stone surfaces — particularly those with polished finishes — can be scratched or etched by the acetic acid.
- Melt Mats: Substituting the power of electricity for chemical reactions, melt mats take two forms: a series of electric wires that lay underneath the walkway stone and radiate heat upwards; or, simple heated mats that lay atop the walkway and melt snow that lands on its surface. Since tearing up your existing walkway to install the circuitry isn’t realistic, a surface heated mat may be the way to go.
- Salt Water-Resistant Sealers: Sealers can be a preemptive strike against salt degradation, provided they are made specifically for stone surfaces. When properly applied, sealers penetrate exterior stone to repel salt and other melting agents, and the water-based formulations also provide all-season weather and UV resistance without endangering the stone or the environment.
- Spring Cleaning Poultice: After Mother Nature dishes out her worst, sometimes your only defense is post-winter cleanup using a poultice — a paste-like material that “draws out” or absorbs stains when applied to porous materials such as natural limestone. While a poultice will attack deep-seated dirt, grime and salt residue, be aware that some stubborn stains may never completely be removed, or etching may occur from some chemical applications. If you encounter these issues, consult with a stone professional to determine additional steps.
Combatting winter’s snow and ice with salt can wreak havoc on your natural stone landscaping. Using these precautions can help with keeping damage to a minimum, as can the tips you’ll find in our eBook, Care and Maintenance of Natural Limestone. Click the button to access your copy now!