How much does it cost to seal and waterproof a chimney?
Ashburn, VA

How much does it cost to seal and waterproof a chimney?

Ashburn, VA

How much does it cost to seal and waterproof a chimney?

$150 – $400cost to seal a chimney
$160 – $420cost to waterproof a chimney
$170 – $820cost to seal & waterproof a chimney

Get free estimates for your project or view our cost guide below:

$150 – $400 cost to seal a chimney

$160 – $420 cost to waterproof a chimney

$170 – $820 cost to seal & waterproof a chimney

Get free estimates for your project or view our cost guide below:
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Daniel Bal
Written by
Daniel Bal
Edited by
Kristen Cramer
Fact-checked by
Tom Grupa

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.

Chimney sealing or waterproofing cost
Factor Professional cost DIY cost
Sealing a chimney $150 – $400 $85 – $240
Waterproofing a chimney $160 – $420 $70 – $200
Sealing & waterproofing a chimney $170 – $820* $100 – $300

*Some pros offer a discount when combining the two services in one visit.

Sealers form a protective layer over a surface, while waterproofing compounds penetrate surfaces and fill gaps where water could enter. Despite these differences, both services are priced similarly, and some pros use the terms "sealing" and "waterproofing" interchangeably.

Get free estimates from chimney repair services near you.

Chimney sealant costs

The average cost of chimney sealant is $35 to $90 per gallon, which covers up to 100 square feet. Although most chimneys have a surface area just under 100 square feet, purchasing two gallons allows you to apply a second coating for maximum protection against water damage.

Chimney sealant cost
Sealant Average cost per gallon
Black Diamond $55
Chimney Saver $90
Flex Seal $35
LastiSeal $60
Masonry Defender $38

Chimney waterproofing costs

The cost of chimney waterproofing compound averages between $20 and $60 per gallon, which covers 90 to 100 square feet. Much like sealant, purchasing two gallons allows for the application of a second coat.

Chimney waterproofing compound cost
Waterproofer Average cost per gallon
ChimneySaver $60
ChimneyRX $38
Eco Advance $22

Chimney sealing & waterproofing cost factors

Factors that affect the cost include:

  • Chimney size – Large, double-flue chimneys cost more to seal due to the extra surface area.

  • LaborChimney sweeps charge $150 to $375 per hour.

  • Accessibility – Labor costs increase for chimneys that are difficult to access due to trees, bushes, or steep rooflines.

  • Repairs – Before sealing or waterproofing, the chimney crown and cap must be assessed to determine if either has water damage and needs to be repaired or replaced.

contractor repairing cracked chimney mortar joints
contractor repairing cracked chimney mortar joints

DIY chimney sealing costs

Sealing or waterproofing a chimney as a DIY project can cost an additional $50 to $150+ for supplies. Most of the tools and supplies can be reused.

Get free estimates from chimney repair services near you.
Chimney sealing & waterproofing tools & supplies
Material Purpose Average cost
Brick cleaner

Seal: Makes sure nothing is in between the sealant and the brick

Waterproof: Allows the compound to better penetrate the brick

$25 per gallon
Safety goggles Protects the eyes from splattering


Reusable:$5 – $60

Disposable gloves Prevents chemical burns and/or irritation $10 (100 count box)
Paintbrush To apply the sealant or waterproofing compound $5 –$15
Sprayer To apply the sealant or waterproofing compound $10 – $25
Ladder To reach the upper half of the chimney $50 – $100+

Chimney sealing & waterproofing FAQs

How often does a chimney need to be sealed?

Chimney sealant should last 15 to 20 years if properly applied. However, it's important to look for signs the sealant may need to be reapplied earlier to avoid costly damage. Warning signs include the following:

  • Water on the inside of the chimney or fireplace.

  • Bricks or mortar on the exterior of the chimney are crumbling or cracked.

  • Musty or damp smell coming from the chimney.

  • Metal parts like the damper or firebox on the interior of the chimney are rusting.

  • Presence of white stains (efflorescence) on the exterior brick of the chimney.

Does sealing a chimney extend its lifespan?

Sealing extends a chimney's lifespan by protecting it against the damaging effects of water. Water eats away at the mortar and can seep into the bricks, expanding them when it turns into ice as temperatures drop. The more protection a chimney has, the longer it will maintain its structural integrity.

Is sealing a chimney the same as waterproofing?

Sealing and waterproofing both protect the chimney from water but in different ways. When waterproofing a chimney, a chemical compound penetrates the bricks, filling spaces water could potentially access. Sealing creates a protective layer on the chimney's surface that prevents bricks from being exposed to water.

How to seal a chimney

Follow these steps to seal a chimney:

  1. Fill any cracks with a masonry crack filler. Allow the brick to dry.

  2. Clean the exterior brick of the chimney with a brick cleaner to remove mold, mildew, and efflorescence. Allow the brick to dry.

  3. Use a paintbrush or garden sprayer to apply sealant or waterproofing compound to the exterior chimney brick. Follow the manufacturer's guidelines regarding coverage.

  4. Use a paintbrush to even out the sealer or waterproofing compound and avoid run-off or dripping.

Getting quotes from chimney sealing professionals

Consider the following recommendations when getting quotes from chimney repair companies:

  • Decide between sealing and waterproofing.

  • Search for at least 3 to 4 in-person quotes.

  • Consider sealing and/or waterproofing the chimney as a DIY project.

  • Read reviews from reputable websites such as HomeGuide and Google. the BBB.

  • Choose professionals who are insured and certified.

  • Request a detailed estimate in writing.

  • Ask for multiple references.

  • Avoid hiring someone who has not assessed the chimney yet still quotes a price.

  • Beware of the lowest quote; lower quotes may reflect a lower quality of work.

Questions to ask

Asking the right questions can help you choose the best contractor:

  • Are you licensed or certified?

  • Do you carry liability insurance?

  • How long have you been in business?

  • What experience do you have with sealing and waterproofing chimneys?

  • Based on your experience, would you recommend sealing or waterproofing? Why?

  • Would it be worth sealing and waterproofing the chimney?

  • Have you worked on a chimney similar to mine?

  • What is the estimated cost of the work?

  • How likely is the estimated cost to increase by the end of the project?

  • How long will it take you to complete the work?

  • How long will the sealing or waterproofing last?

  • Do you offer a warranty? If so, does your guarantee include fixing issues that arise after the work is completed?