Chimney waterproofing involves applying specialized, vapor-permeable siloxane-based sealants to the masonry and elastomeric coatings to the concrete crown. This prevents water intrusion that causes freeze-thaw damage while allowing trapped moisture to escape. Proper sealing extends the lifespan of bricks, mortar, and flashing.
Some parts of your home are more vulnerable than others. Because masonry chimneys are made from porous materials like brick and stone, they absorb moisture like a sponge. The best way to protect your chimney is to apply a waterproof sealant.
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.
Cost to seal or waterproof a chimney
Chimney waterproofing costs $160 to $420 on average, including labor and materials. The cost to seal a chimney is $150 to $400 if done by a professional. The DIY cost to seal or waterproof a chimney is $85 to $300 for one gallon of sealant or waterproofing compound and supplies.
No, it is not normal for a chimney to leak, even a little, during heavy rain. A chimney in good condition is designed to keep water from seeping into your home, so a leak indicates that it is not functioning properly.
Homeowners insurance is one of the most important types of property insurance. It includes coverage for many different types of damage to your home and its contents, including leaks in your chimney. It's also mandatory to have if you're trying to get a mortgage on a home.
Yes, chimney balloons absolutely work. They act as heavy-duty, inflatable plugs that block drafts, prevent expensive conditioned air from escaping up the flue, and keep out unwanted pests and debris.
The longevity of chimney sealing/waterproofing can vary depending on where you live and what type of elements and weather conditions your chimney is subjected to. If the job is done right – and with the right industry-grade product – most customers will be good for 8 – 12 years.
Water damage drives some of the most expensive chimney repairs:
To stop rain from coming down your chimney, install a stainless steel chimney cap (cowl), which acts as a physical shield over the flue. If you already have a cap, check the chimney crown (the cement wash on top) for cracks and ensure your roof flashing is sealed to prevent leaks.
Yes, mice can absolutely come down your chimney. Because mice are agile climbers and can squeeze through openings as small as a dime, they easily scale the outside of a chimney and slip inside seeking warmth and nesting sites.
The best chimney waterproofing products fall into two categories: Masonry Sealers (for vertical brick/stone) and Crown Repair Coatings (for the cement top of the chimney).
The single most common reason for an older brick chimney to leak is erosion. Eroding brick and crumbling mortar can leave the upper end of your chimney exposed to the weather, so that water begins to get inside your chimney through the gaps when it rains.
Implementation can be challenging, requiring precise application and suitable conditions. There's a risk of trapped moisture, which can induce mold growth and material failure. Some waterproofing methods limit flexibility post-application, potentially causing structural issues.
You can do that with stucco or by using a waterproof paint. Boat paint might be overkill, but it should work like a charm. There's also a special hybrid product from Saver Systems that has some solids in it (Chimney Saver for Concrete Blocks).
The "7 Times Rule" for chimneys dictates that the cross-sectional area of a masonry chimney flue cannot exceed seven times the area of the appliance’s vent connector (draft hood outlet) to ensure proper drafting and prevent acidic condensation. If the chimney is too large, it must be relined to prevent damage from cooling gases.
If you've been hearing a dripping sound coming from your chimney after a heavy rain or noticed moisture and stains on the wall near your fireplace, you likely have an issue that must be fixed by a professional. Rainwater trickling into your fireplace is not normal.
Yes, you absolutely need a rain cap (and a Chimney Cap vs Rain Hat generally comes with a wire mesh) on your chimney. It serves as your system's primary defense against expensive weather damage and safety hazards.
To stop water from coming down your chimney, you first need to identify where the water is entering. The most common entry points are the top of the chimney, the masonry, or the roof flashing. Taking the following steps can help resolve the problem:
Most homeowners insurance policies will cover chimney repairs caused by sudden and accidental events, such as fires, storms, or falling trees. Damage from wear and tear, poor maintenance, or construction defects is usually not covered.
If averaged out, a chimney can last between 20-50 years, while some materials and some structures can last longer. Several factors will determine the lifespan of a chimney: how well it is taken care of, what materials were used in constructing the chimney, and local weather conditions.
The cost to replace a chimney typically ranges from $3,100 to $15,400, depending on the type and size of the chimney.
Yes, mice absolutely can and do come down chimneys, utilizing them as warm, sheltered, and vertical pathways to enter homes. Mice are excellent climbers that can scale the exterior brickwork, enter through gaps or cracks, and move down the flue into the fireplace or attic.
Installing a stainless steel chimney liner typically costs between $900 and $3,800, with a national average of roughly $2,500 for professional installation. Costs generally range from $20 to $90 per linear foot for materials, depending on whether the liner is rigid or flexible, with total project prices varying based on chimney height and job complexity.
The Chimney Cap: First Line of Defense
At the top of the chimney, the chimney cap is the most critical component for keeping rain out. This metal covering, typically made of stainless steel or copper, sits above the chimney flue like a roof.