As one of the oldest construction materials still in use today, natural stone can be found in many outdoor structures. The Seven Wonders of the Ancient World all featured natural stone, and this inspired Roman and later Italian architects to continue using limestone, travertine, marble, granite, and other metamorphic rocks to build ancient and magnificent structures such as the Colosseum. If you travel to Rome and visit the Colosseum these days, you will notice very few of the exterior travertine blocks, which were extracted from the quarries at Tivoli, have retained their original golden hue, and this is because sealant for natural stone would not be formulated until many centuries later. Had ancient masonry and stonework experts been able to apply sealant, the magnificent structures they built would be in much better shape today. If you have stone in the outdoor areas of your home, it’s best to keep it sealed.
Why Outdoor Natural Stone Must Be Sealed
Many of the entrances, stairs, columns, and exterior fascia of the Rockefeller Center in New York City are made of Swedish green marble, a very attractive and porous stone. Without a proper seal, this exotic marble would not be able to withstand the heavy foot traffic, acid rain, snow, and air pollution associated with Manhattan. With a couple of exceptions, sealing is a must for homeowners who expect to keep their outdoor natural stone in good shape. The main argument in favor of sealing outdoor stone is moisture. Even in the driest regions of Arizona and California, night condensation will result in moisture, which will penetrate the stone’s surface and increase the potential for cracks and fissures.
Types of Seals for Outdoor Natural Stone
For the original seal, the fabricator and contractor may choose impregnating, solvent, or water-based sealant depending on the type of stone and its finish. For example, flagstone pathways installed in coastal homes require a seal that is resistant to saltwater. Glossy and polished stone will require a topical sealant.
Resealing Outdoor Stone
Homeowners can protect their outdoor stone by applying the same measures as they do indoors, which means using a stone-safe sealer that has been formulated for this specific purpose. If you don’t know how to seal natural stone, all you have to do is spray Granite Gold Sealer® on the surface in 3-foot sections, then immediately wipe it into the stone with a lint-free cloth. Make sure to not allow the sealer to dry, as it will cause hazing. Instead, buff the sealed area with a clean lint-free cloth.
When Sealant Should Not Be Used Outside
The only two exceptions to the outdoor sealant rule are fieldstone and slate in high sunshine regions such as Arizona and Florida. Sealing fieldstone would be overkill unless you absolutely know all the rocks are metamorphic and porous. Besides, fieldstone is easy to replace if needed. In the case of slate used outside, homeowners in Arizona will notice that the seal tends to flake off after a few weeks of heavy sunshine. This is due to high UV levels. All other types of natural stone should be sealed when installed outside.
Make sure you also clean your outdoor stone regularly with an outdoor stone cleaner that is safe to use on granite, slate, limestone, and all other types of natural stone. If you’d like more information on the high-quality stone care products offered by Granite Gold®, give us a call today at 1-800-475-STONE.