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Chimney Waterproofing

AtoZChimneySweep-SacramentoCA-ChimneySaverChimney Saver Water Repellent

Who’s ever heard of waterproofing a chimney, and why would they want to do it?!

The Problem:

Bricks are very porous and readily absorb water.

Bricks are very porous and readily absorb water.

Did you know that water causes more damage to a masonry chimney than any other single element that nature can throw at it? Dollar for dollar, more money is spent repairing water-damaged chimneys than any other type of repair we do! The phrase “an ounce of prevention is better than a pound of cure” never rang truer than when it comes to protecting your home’s very expensive masonry chimney!

How does water damage a masonry chimney?

Did you know that a brick is a lot like a sponge? If you were to weigh a brick while dry, and then re-weigh it after setting it in a bucket of water for a few hours, it will have almost doubled its weight because of all the water it has absorbed! Like a sponge, bricks are very porous and readily allow themselves to become completely saturated with water. Why is this a problem?

Once your chimney’s brickwork is completely saturated with water, several things can happen:

Ceiling damage due to water leaks is common and can be expensive to replace.

Ceiling damage due to water leaks is common and can be expensive to replace.

1. Water Leaks: Once you’re masonry chimney is fully saturated, rainwater often finds its way into your home! Leaks in the ceiling and walls and the flooring in the vicinity of the chimney are common, and can cause thousands of dollars in damage to your home! Dry rot, mold, drywall repair and replacing flooring due to water damage is expensive! Water damage specific to your chimney often include the following:

Water damage can erode the mortar joints that hold your flue tiles together.

Water damage can erode the mortar joints that hold your flue tiles together.

2. Liner Damage:Water infiltration into your chimney’s chase often damages your terra cotta chimney liner by leeching out and eroding the mortar joints that glue your flue tiles together. Once these mortar joints are eroded, the open voids that result can allow carbon monoxide, creosote, and in some cases, open flames to escape your flue and cause a structural fire! A chimney with open voids in the flue tile mortar joints should NOT BE USED UNTIL IT IS REPAIRED with HeatShield® or relined with a stainless steel liner.

Rusted dampers need to be removed.

Rusted dampers need to be removed.

3. Steel Dampers Rust: Your fireplace’s damper is an important component to keeping the cold air out and the warm air in. Water entry often causes dampers to either rust solid so they can no longer be opened or closed, or eat rust holes right through them, causing air leakages and severe energy loss! When this happens, the old rusted damper must be removed (or bypassed), and a new top-sealing damper will need to be installed.

A chimney with freeze/thaw damage.

A chimney with freeze/thaw damage.

4. Freeze/Thaw Damage: If your chimney’s brickwork is saturated with water and outdoor temperatures fall below freezing (usually overnight), your chimney will likely suffer freeze/thaw damage. Freeze/Thaw is when the water within your chimney’s brickwork freezes and expands. This slight expansion is enough to cause extensive damage to your chimney’s brickwork, from small cracks and fissures to large chunks of your chimney’s bricks spalling (flaking off in large chunks)!

Efflorescence on the interior of a chimney.

Efflorescence on the interior of a chimney.

5. Efflorescence: Once absorbed into your chimney’s brickwork, water will dissolve tiny minerals and salts that make up the structure of your chimney’s masonry. As weather conditions warm up and dry out, the water within your chimney’s bricks will migrate to the outside surface of your chimney and evaporate, leaving behind the white salt and mineral stains. These ugly stains are called efflorescence. Efflorescence is not only unsightly, but is also an indicator that water is eroding and weakening your chimney’s masonry structure each time it rains! Left unchecked, the mortar (the glue) that holds your chimney’s bricks together will turn sandy and fail. Sometimes this damage is so severe, the entire chimney must be torn down and rebuilt from scratch.

The Solution:

ChimneySaver water repellent

ChimneySaver water repellent

Needless to say, when it comes to keeping water out of your masonry chimney, an ounce of prevention is better (and far cheaper) than a pound of cure! ChimneySaver Waterproofing is one of the steps to keeping Mother Nature’s damaging rainwater at bay!

Unlike typical concrete sealants that can accelerate damage to your chimney by trapping water vapors inside your chimney, ChimneySaver is specially formulated to form a semi-permeable membrane that allows your chimney’s brickwork to breathe! It keeps new water from penetrating, while allowing any water that’s already trapped within the brickwork to escape!

ChimneySaver repels water while allowing trapped water vapors to escape.

ChimneySaver repels water while allowing trapped water vapors to escape.

This semi-permeable membrane is important because moisture from a variety of sources is always present in masonry and concrete. Traditional sealants form a water-resistant surface film which traps these water vapors inside. If these vapors can’t escape, they will likely contribute to scaling, spalling and freeze/thaw damage! ChimneySaver is a 100% vapor- permeable water repellent that penetrates and lines the brick’s microscopic masonry pores.

ChimneySaver is 100% breathable.

ChimneySaver is 100% breathable.

ChimneySaver contains patented siloxanes small enough to penetrate most masonry pores up to ¼” or more. These special siloxanes from a strong bond with the silica in masonry and concrete. Because of this bonding process, one application of ChimneySaver provides up to ten times the water repellent protection of typical sealers while at the same time, maintaining the masonry’s breathability.

10 Year Limited Warranty:

Saver Systems warrants that ChimneySaver water repellent will exhibit a water repellent effect for ten years from the date of application if applied according to label instructions and if minimum application requirements are met. (See brochure for complete warranty details.)


If your chimney is experiencing water leaks, liner damage, freeze/thaw damage, or efflorescence, ChimneySaver is one of the most important steps available for preventing water damage.

Note, however, that no water repellent is a substitute for good construction and workmanship. The first step in preventing water damage is to make necessary repairs as needed by installing a chimney cap and repairing structural cracks, damaged crowns, flashing, deteriorated bricks, and mortar joints. The second step is to protect porous masonry from further water penetration by applying ChimneySaver Water Repellent.


Crumbling mortar in the chimney, if not too advanced, could be repaired with tuckpointing. Our skilled personnel can advise you about your situation and make the necessary chimney repairs.

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Thank you for the good job you did cleaning my dryer vent! The dryer dries much faster now with far less wasted energy! I also now am able to relax knowing I don’t have such a fire hazard anymore.

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