Why You Should Not Seal Your Exterior Limestone

Limestone is one of the most enduring and beautiful natural stones used in architecture. From ancient European cathedrals to historic American landmarks, limestone has withstood centuries of weather, wear, and time. Yet today, many homeowners and contractors feel pressured to “protect” exterior limestone by sealing it. While this seems like a sensible idea, sealing limestone—especially outdoors—can actually do more harm than good.

In this post, we’ll explain why you should think twice before sealing your exterior limestone, and how this natural stone is built to last without synthetic interference.

1. Limestone Is Meant to Breathe

Limestone is a naturally porous material. Its pores allow moisture to enter and escape as the environment changes—a natural “breathing” process that helps it withstand the elements. When you apply a non-breathable sealer, you block this moisture exchange. Trapped water inside the stone can lead to:

• Efflorescence (white powdery buildup)

• Cracking and spalling in freeze-thaw cycles

• Long-term structural weakening

Sealing essentially suffocates the stone, which often accelerates the breakdown it was supposed to prevent.

2. Limestone Will Outlast Us—and Any Sealer

Limestone can last for hundreds, even thousands of years when installed correctly and cared for naturally. The lifespan of a sealer? Typically 1 to 5 years—and then it needs to be stripped and reapplied.

This short-term solution leads to a long-term maintenance burden. It’s worth considering: limestone is likely to be here long after we’re gone. Adding a man-made coating to it doesn’t preserve it; it only complicates its care.

3. Algae, Mold, and Moss Will Still Grow—Even on Sealer

A common myth is that sealers prevent biological growth. In reality, algae, moss, mold, and lichen can and will grow on top of the sealer. In many cases, the sealer provides a perfect film for these organisms to anchor to—especially in shaded or humid areas.

Once growth attaches to the sealer, it can be even harder to remove than if it had grown on bare stone. Cleaning it off often requires chemicals or aggressive scrubbing, which can damage both the sealer and the limestone beneath.

4. Sealing Can Alter the Stone’s Appearance

Limestone is prized for its natural, earthy beauty. But sealers can:

• Darken the color

• Add a glossy, artificial shine

• Yellow over time due to UV exposure

• Create uneven or blotchy finishes as they wear

These aesthetic changes are often irreversible. Removing sealers requires chemical stripping or grinding, which can permanently scar the stone.

5. Sealed Limestone Can Look Dirtier, Faster

Some sealers, especially topical ones, attract dirt and grime. Once the surface begins to wear unevenly, you may notice blotchy, dirty patches that weren’t there before sealing.

In the long run, you may find yourself cleaning a sealed limestone surface more often than an unsealed one.

6. Maintenance Becomes a Lifelong Chore

Sealing is not a one-and-done solution. It sets up a continuous cycle of:

• Monitoring wear and tear

• Periodically resealing every few years

• Addressing buildup and discoloration

• Paying for labor-intensive removal if things go wrong

By sealing, you’re signing up for more work, not less.

7. Not All Sealers Are Safe for Limestone

Limestone is sensitive to certain chemicals. Using the wrong type of sealer can:

• Cause permanent staining (especially oil-based sealers on light stone)

• React poorly with UV exposure or moisture

• Alter the chemical structure of the surface

Even when using a sealer labeled “stone-safe,” it’s easy to make mistakes that lead to costly restoration.

8. Health and Environmental Hazards

Many sealers contain volatile organic compounds (VOCs) that release harmful fumes during and after application. These VOCs can:

• Pose health risks during installation

• Pollute the surrounding air and groundwater

• Create runoff that damages nearby landscaping

Choosing not to seal is often the greener, safer, and healthier choice—for you, your family, and the planet.

Let Limestone Be Limestone

Limestone has survived for millennia without synthetic coatings. Instead of sealing, focus on natural, time-tested care methods:

• Ensure proper drainage and water runoff

• Clean periodically with a pH-neutral, stone-safe solution

• Avoid abrasive tools or high-acid cleaners

• Embrace the stone’s natural patina and character

Preserve the timeless integrity of your limestone by not sealing it. Trust in the same qualities that made it the material of choice for ancient builders—because this stone was built to last.

Have questions about limestone care or cleaning? Contact us today for expert, no-pressure advice. We specialize in helping you maintain your stone naturally and effectively—without unnecessary chemicals or coatings. 312-384-0044