Chimney leak repair: find where the water gets in
HomeGuide prices sealing chimney leaks at $150 to $500 and Fixr gives $150 to $500 for fixing a leaky chimney, while chimney flashing repair costs $300 to $1,800, according to HomeGuide. Fixr's newer roof leak guide puts repairing a leaking chimney at $200 to $3,500. HomeGuide says leaks typically occur where the chimney meets the roof, often due to damaged flashing or failed sealants, and Fixr says cracks in the mortar or the bricks themselves can also let water in. The Chimney Safety Institute of America (CSIA) says water causes more damage to masonry chimneys than fire.
| Where the water gets in | Repair | Cost | Source |
|---|---|---|---|
| Flashing, where the chimney meets the roof | Repair or replace the flashing | $300 to $1,800 | HomeGuide |
| Flashing | Patch / replace | $200 to $300 / $300 to $800 | Fixr |
| Crown | Minor repairs / full replacement | $150 to $700 / $1,000 to $3,000 | HomeGuide |
| Cap | Replace the cap, installed | $200 to $850 | HomeGuide |
| Mortar joints | Re-mortar / repoint | $150 to $500 / $500 to $2,500 | Fixr |
| Brick faces | Spalling repair | $1,000 to $2,500 | Fixr |
| Chase on a prefabricated chimney | Chase cover, installed | $300 to $700 | HomeGuide |
| Whole masonry surface | Seal and waterproof | $170 to $820 | HomeGuide |
Chimney leak repair cost
HomeGuide's chimney repair guide prices sealing chimney leaks at $150 to $500 and says waterproofing the chimney completely can reach $800 or more.
Fixr's roof leak guide puts repairing a leaking chimney at $200 to $3,500, with minor work, like replacing a chimney cap, at the low end and major work on damaged bricks, mortar or flashing at the high end.
Why is my chimney leaking when it rains?
CSIA's four recommendations for preventing water damage cover the cap, the crown, the flashing and waterproofing the brick. CSIA says water penetration can cause broken brickwork, rusted fireplace dampers, rotted wood and cracked flue liner systems. It calls water damage to chimneys usually a slow process that is easily ignored until problems have become quite serious.
Fixr says chimney leaks are most often caused by damaged flashing. The Brick Industry Association (BIA) says chimneys are often exposed to wind-driven rain and to water running down the exterior walls from the crown or coping.
Flashing: where the chimney meets the roof
CSIA describes flashing as the seal between the roofing material and the chimney that prevents rain water from running down the chimney into living spaces. Fixr says superficial flashing damage can be patched; HomeGuide says rusted metal, missing sections or water infiltration beneath shingles may call for full replacement.
Where the 2021 International Residential Code (IRC) is adopted, flashings must be installed in a manner that prevents moisture from entering the wall and roof at penetrations through the roof plane (R903.2). A cricket or saddle is required on the ridge side of a chimney more than 30 inches wide measured perpendicular to the slope (R903.2.2); chapter 10 words the trigger differently (R1003.20). Prices, warning signs and the full code table are on our chimney flashing repair page.
Crown and cap: the top of the chimney
CSIA says a well-designed cap will keep out rainwater, and that crowns should project beyond all sides by two inches to help prevent erosion of the brick and mortar in the chimney's vertical surfaces. Fixr's inspection guide says that when the crown is damaged, the excess water can cause bricks to separate and damage clay tiles.
The 2021 IRC requires masonry chimneys to have a concrete, metal or stone cap, a drip edge and a caulked bond break around any flue liners, with the cap sloped to shed water (R1003.9.1). BIA Technical Notes 19B says the cap should be sealed at the cap and flue liner interface to reduce the potential for water penetration.
HomeGuide prices minor crown repairs at $150 to $700 and a full crown replacement at $1,000 to $3,000; Fixr puts crown repairs at $750 to $1,000. A replacement cap costs $200 to $850 installed, per HomeGuide, or $300 to $600 per Fixr. Details are on our chimney crown and chimney cap pages.
Brick and mortar joints
CSIA says common brick is like a sponge, absorbing water and wicking moisture to the chimney interior, and that defective mortar joints can greatly increase the tendency to absorb and convey water. BIA, writing about brick walls in Technical Note 7, puts the weight on the joints: when water passes through brick masonry walls, it typically does so through minute separations between the brick units and the mortar joints, and highly absorbent brick will absorb some water but does not contribute to bulk water penetration through a wall.
Fixr says mortar acts as a barrier against moisture and prices re-mortaring at $150 to $500 and repointing at $500 to $2,500. Fixr describes spalling as moisture getting into the masonry and leading to cracks and crumbling sections, and prices the repair at $1,000 to $2,500; HomeGuide gives $1,000 to $3,500. HomeGuide lists moisture trapped behind non-breathable sealants among the common causes of spalling.
Waterproofing and sealing a chimney
The sources do not fully agree. CSIA lists waterproofing as one of its four measures to prevent major water damage. BIA's Technical Note 6A says a water repellent coating is not necessary to achieve water resistance in brickwork under normal exposures where proper material selection, detailing, construction and maintenance have been carried out. It also says water repellents can be useful for chimneys, parapets and other brickwork that is particularly vulnerable to water absorption and penetration, especially in climates that receive large amounts of rain.
BIA's conditions and limits for a clear water repellent on brick:
- It may be recommended on chimneys in climates with a driving rain index above 3, and on sloped or horizontal projections where water and snow can accumulate.
- Correct the conditions contributing to water penetration before applying a coating.
- It is rarely effective and not recommended in place of replacing failed sealant, repointing cracked or disintegrated mortar joints, replacing spalled or cracked brick, or surface grouting separations between brick and mortar.
- Penetrating water repellents seldom stop water through cracks more than 0.02 inch wide, and their effectiveness under wind-driven rain is limited.
- If one is used, BIA recommends siloxanes, and it discourages film-forming coatings, particularly in freezing climates.
HomeGuide prices sealing a chimney at $150 to $400, waterproofing at $160 to $420 and both together at $170 to $820. It says the crown and cap must be assessed for water damage before sealing or waterproofing, and that chimney sealant should last 15 to 20 years if properly applied. Fixr prices chimney sealing at $150 to $500 and says it can be useful where there is heavy rainfall or frequent storms.
Chimney chase covers and wood framing
HomeGuide describes a chase cover as a piece of metal that fits on top of a prefabricated chimney, with an opening in the middle covered by the chimney cap, and prices one at $300 to $700 installed. Fixr also says some chimneys have wooden sections around the outside that rot from heavy rain and moisture, which poses a threat of leaks; it prices that repair at $200 to $500.
Condensation in a gas appliance flue
Where the 2021 IRC is adopted, its fuel gas chapter says that where an appliance is permanently disconnected from an existing chimney or vent, or where an appliance is connected to an existing chimney or vent during the process of a new installation, the chimney or vent shall be resized as necessary to control flue gas condensation in its interior (G2425.15.1). In those cases the flue liner, chimney inner wall or vent inner wall must also be continuous and free of cracks, gaps, perforations or other damage that would allow the escape of combustion products, including gases, moisture and creosote (G2425.15.2). HomeGuide says professionals recommend insulating steel flues, especially around high-efficiency heaters and stoves, to reduce corrosive condensation.
For gas appliances, the same chapter requires masonry chimneys to be lined with an approved clay flue lining, a chimney lining system listed and labeled to UL 1777, or other approved material that resists corrosion, erosion, softening or cracking from vent gases at temperatures up to 1,800°F. Flues serving listed gas appliances with draft hoods, Category I appliances and other gas appliances listed for Type B vents may instead use a lining system listed for use only with such appliances (G2427.5.2). Liner types and prices are on our chimney liner page.
Chimney leak inspection
HomeGuide's general list of signs that a chimney needs repair includes visible cracks in the chimney or crown, water stains on walls or ceiling near the chimney, rust on the damper or firebox, and crumbling mortar. Its waterproofing guide lists signs that chimney sealant may need reapplying: water on the inside of the chimney or fireplace, a musty or damp smell and white stains (efflorescence) on the exterior brick.
HomeGuide says to request a level 2 inspection if you see signs of damage, and prices one at $250 to $600 for up to two flues or fireplaces. It adds a video inspection of the internal parts and hard-to-reach areas to a full level 1 assessment. Fixr prices a level 2 inspection at $150 to $1,000 and says it is warranted after a recent significant storm. See our chimney inspection guide for the three levels.
How do you fix a leaking chimney?
Fix the part that lets the water in. Fixr says a leak repair means repairing or replacing the flashing and possibly resealing the damaged area, and BIA says to correct the conditions contributing to water penetration before any coating goes on. CSIA lists four preventative measures, not a repair sequence:
- Install a chimney cap. CSIA says a well-designed cap will keep out rainwater and also prevent birds and animals from entering and nesting in the chimney.
- Repair or replace a damaged chimney crown. CSIA calls a cast crown with an expansion joint an ideal long-lasting replacement for the more commonly found sand and mortar washes.
- Repair or replace flashing. CSIA describes it as the seal between the roofing material and the chimney.
- Waterproof your chimney. Under this item CSIA says common brick is like a sponge, absorbing water and wicking moisture to the chimney interior. BIA's limits on water repellents are above.
Fixr does not recommend that homeowners take a DIY approach to chimney repair, saying it can be very dangerous to get on the roof without the necessary tools and experience. HomeGuide says minor tasks like applying waterproof sealant might be DIY-friendly, but repointing and structural repairs should be handled by certified professionals.
Who to call for a chimney leak
For flashing, HomeGuide says both professional roofers and certified chimney sweeps can do the work, and recommends a contractor licensed and insured for both roofing and chimney work. For chimney repair in general, it suggests a contractor certified by CSIA or a member of the National Chimney Sweep Guild, and written estimates from at least three contractors. Repair prices beyond leaks are on our chimney repair cost guide, and flue cleaning is covered on our chimney sweep page. To get a price for your leak, use the form below and we will send your request to a company that serves your ZIP code.
Chimney leak repair: common questions
How much does it cost to fix a leaking chimney?
What is placed around a chimney to prevent leaks?
Do chimneys leak in heavy rain?
How to tell if your chimney is leaking?
Does homeowners insurance cover chimney leaks?
How much does it cost to seal a chimney?
Sources
- Chimney Safety Institute of America, "Four Low-Cost Recommendations to Prevent Major Water Damage", June 11, 2010: csia.org
- Brick Industry Association, Technical Notes 6A, "Colorless Coatings for Brick Masonry", August 2008: gobrick.com
- Brick Industry Association, Technical Note 7, "Water Penetration Resistance: Design and Detailing", November 2017: gobrick.com
- Brick Industry Association, Technical Notes 19B, "Residential Chimneys: Design and Construction", reissued April 1998: gobrick.com
- International Code Council, 2021 International Residential Code, chapter 9, roof assemblies (R903.2, R903.2.1, R903.2.2): codes.iccsafe.org
- International Code Council, 2021 International Residential Code, chapter 10, chimneys and fireplaces (R1003.9.1, R1003.20): codes.iccsafe.org
- International Code Council, 2021 International Residential Code, chapter 24, fuel gas (G2425.15, G2427.5.2): codes.iccsafe.org
- HomeGuide, "How much does chimney repair cost?", January 22, 2026: homeguide.com
- HomeGuide, "How much does chimney flashing repair cost?", February 10, 2026: homeguide.com
- HomeGuide, "How much does it cost to repair or replace a chimney crown?", February 9, 2026: homeguide.com
- HomeGuide, "How much does a chimney cap cost?", February 9, 2026: homeguide.com
- HomeGuide, "How much does it cost to seal and waterproof a chimney?", February 9, 2026: homeguide.com
- HomeGuide, "How much does a chimney inspection cost?", February 9, 2026: homeguide.com
- HomeGuide, "How much does a chimney liner cost to install?", February 9, 2026: homeguide.com
- Fixr, chimney repair cost, updated January 31, 2025: fixr.com
- Fixr, cost to repair roof leaks, updated January 27, 2026: fixr.com
- Fixr, chimney inspection cost, updated August 29, 2025: fixr.com