Your Guide to Chimney Waterproofing and Why It’s Important

Even though your chimney is designed to withstand extreme temperatures on the inside, it’s just as susceptible to exterior damage as the rest of your home. Snow, rain, and humidity can wear away at masonry over time, leaving you with structural and safety issues. Chimney waterproofing is an effective way to prevent water damage—but homeowners often overlook its importance. In this guide, you’ll learn the different ways moisture affects your chimney, how chimney waterproofing combats damage, and the steps involved in waterproofing.

How Does Moisture Affect Your Chimney?

Despite their strength and durability, bricks and mortar are porous materials that can absorb moisture. Exposure to rain and snow can wear down your brickwork and cause issues like cracking, spalling, crumbling mortar, and even water damage inside your home. With every freeze/thaw cycle in the winter, the moisture inside your masonry expands and deepens cracks, leading to more severe damage like structural instability over time.

Common Signs of Chimney Water Damage

Here are some telltale signs that your chimney has a moisture problem:

Crumbling bricks, concrete blocks, or stones
Cracking or missing sections of mortar joints
White efflorescence on the chimney exterior
Stains or discolored areas on the chimney
Spalling or missing bricks
Signs of moisture, like discoloration or bubbling, on interior chimney walls
Leaking water inside your firebox
A musty smell coming from your fireplace
Mold or mildew inside near your chimney

If you notice any combination of these warning signs, it’s time to consider repairing and waterproofing your chimney.

Why Should You Waterproof a Chimney?

Many homeowners see waterproofing as an optional step for their newly built or repaired chimneys. But chimney waterproofing is a critical step in protecting your investment. Here’s what chimney waterproofing can do for your home:

Prevent Further Damage

Waterproofing your chimney is the best way to prevent ongoing deterioration from moisture exposure. Unprotected masonry will continue eroding over time, which can require expensive repairs or even a complete rebuild. Chimney waterproofing can also help prevent issues inside your home, such as mold and mildew, rotting wood, and damage to interior walls and ceilings.

If your chimney experiences too much water damage over time, you may have to tear it down and replace it entirely—which can set you back thousands of dollars. A properly waterproofed chimney can last for decades with minimal maintenance. Waterproofing preserves structural stability and reduces the need for costly repairs.

Improve Efficiency

Moisture inside your flue liner can reduce airflow, making it more difficult for smoke and harmful gasses to escape. Keeping your flue dry and smooth can improve performance, reduce backdrafts into your home, and keep you and your family safe.

Increase Curb Appeal

Those fresh, clean lines on a new or tuckpointed chimney make your home more attractive from the street. Waterproofing can preserve the look of your chimney, prevent unsightly staining and cracking, and protect your home’s value.

Image of a worker tuckpointing a residential chimney.

How to Waterproof Your Chimney

Chimney waterproofing is a simple process that brings long-lasting results. Here’s how to do it:

Hire a Professional for Chimney Waterproofing

Consult a certified chimney specialist for inspection and comprehensive waterproofing service tailored to your chimney’s specific damage and structure. Professionals have the proper equipment, like lift buckets and scaffolding, to safely access and treat all exterior chimney surfaces.

At Approved Home Improvements, our team has extensive experience with chimney waterproofing. Our team assesses your masonry’s water damage, performs seamless repairs, and applies the appropriate waterproofing material for your situation. We can also rebuild or seal your chimney crown and attach a cap to prevent water runoff into your home.

Waterproof the Crown and Add a Chimney Cap

Even if your masonry is coated in chimney sealant, water can leak into the top of your flue or seep into the crown. To prevent moisture damage from above, seal your chimney crown with a waterproofing material designed for mortar or concrete. Then, install a properly-sized chimney cap over the flue opening. Caps deflect rainwater and prevent animals and debris from entering the chimney system. Coupled with a waterproofed chimney stack, a sealed crown and cap can keep your chimney and home dry even in rainy or snowy weather.

Perform Chimney Sealing or Use a Water-repellant

There are two ways to protect your masonry against moisture damage: sealing the entire surface or using a water-repellant. Sealers coat your brickwork with a thick, waterproof layer that keeps water out, while water repellants add a thinner moisture barrier that permeates the brick and mortar. Choosing the wrong type of sealer can make issues worse, which is why you should bring in a professional to assess your current structure and provide recommendations.

Repair Damage

Before you can apply any waterproofing products, you need to repair any cracks, missing mortar, damaged bricks, and other masonry issues. Your chimney may require tuckpointing and repointing, brick replacements, or a rebuild in certain areas. These repairs will give you a clean slate before the waterproofing materials are applied and help ensure the waterproofing materials don’t lock in existing moisture.

Learn more about how chimney sealantprotects your masonry and if it’s the right waterproofing treatment for your home.

Read Our Guide

Approved Home Improvements Can Help Your Chimney Stand Up to the St. Louis Weather

Approved Home Improvements understands the importance of chimney waterproofing because we’ve seen how St. Louis humidity and rain can damage brickwork. Our experienced team performs high-quality repairs and preserves them with chimney waterproofing to ensure they last for years. Whether you need to seal a newly built chimney in your home or restore and waterproof an existing chimney structure, our team has the tools and expertise to help.