Water is a Masonry Chimney’s Worst Enemy

Brick and stone are used in construction because of their aesthetic and durability, however, these materials, along with mortar, are susceptible to water damage and need to be maintained to prevent failure.  Since restoration or reconstruction is costly, it is important to keep a watchful eye on any chimneys in a home.

Bricks, stones, and mortar all absorb rainwater to some degree based on their density and hardness. Some of these masonry materials, such as soft-type brick, absorb and retain water more easily than hard-type brick. Unfortunately, many builders use soft brick since the cost is lower, and problems usually won’t show up for several years after a structure has been built and they are long gone.

Spalling bricks and missing mortar due to water penetration

All types of masonry should be treated with a professional water-repellant sealer every two to five years. The sealer will reduce penetration of water into the masonry by causing the water to bead up. This process alone can save homeowners thousands of dollars. Without water repellant, the masonry will absorb moisture, go through freeze/thaw cycles, and at some point will begin to spall (faces pop off). In severe cases, mortar is washed out and bricks may fall out.

The next area of concern is the cement cap, otherwise known as a wash, splay, or crown. The cement cap acts as a roof for a chimney, and if properly built will shed water away from the top portion of the chimney rather than directing rainwater onto the masonry. This area is the most common space to find damage to the masonry since most cement caps are not built properly and to International Residential Code requirements. The IRC requires a 4” thick cap with a 2” drip edge and drip channel, with bond breaks around the flue tiles to allow for expansion. A properly built cap will last for many years and will help protect the masonry below it.

Finally, faulty flashing is often a source of leaking into the attic or other floors of the home. If water damage is found next to a chimney at the ceiling area, suspect the flashing as the first place to look. Gaps or missing pieces of flashing, or unsealed areas will likely be areas of concern that need to be addressed with sealant, repair, or replacement.

If your chimney is spalling, has deteriorated mortar,  a cracked or improperly built cement cap, or leaking issue, contact your local chimney professional for help. 

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Marge Padgitt is a 40-year chimney industry veteran and the author of Wood-Fired Heating and Cooking. Website: www.chimkc.com. 

Lighting Damaged Chimneys in Storm August 28

Some of the lightning strikes throughout the greater Kansas City area last night hit chimneys. 

A lightning strike caused major
damage to this chimney exterior
and interior

Pieces of bricks on the ground and roof, or blown out sections of a chimney are signs that a recent event occurred and the chimney may have been hit by lightning.

In some cases the damage is so severe that the chimney must be torn down and rebuilt. In other cases where there are only a few damaged bricks or stones these can be removed and replaced with new bricks.

When lightning strikes a chimney the evidence is usually obvious. There is always an entrance and exit point. The entrance point, usually found near the top of the structure, will likely be a large hole with burn marks, and may include large cracks through the masonry or blown out sections of stones or bricks. The exit point is usually found somewhere within the chimney structure in the flue, smoke chamber, firebox, or even the outer hearth inside the house. 

Damage not so visible from the ground -
lightning hit the top of the chimney and
pushed a brick out on the back side

A professional chimney inspector should examine any chimney that has been damaged by lighting. The chimney sweep should perform a Level II internal chimney inspection with a chimney camera system in order to see if any interior damages have occurred which make the fireplace, furnace, or water heater flue unusable. Only persons trained specifically on chimneys can identify chimney damages properly and provide the needed documentation for an insurance claim.  Lighting and chimney fire damage to chimneys is covered by homeowner's insurance.

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Marge Padgitt is the president and CEO ofHearthMasters, Inc. dba Padgitt Chimney & Fireplace. She is a CSIA Certified Chimney Sweep and NFI Certified Wood- burning Specialist. Contact Marge at hearthmastersboss@gmail.com.

Repair damaged chimneys quickly to avoid additional expense

Masonry chimneys should be repaired immediately following storm or chimney fire damage in order to avoid more costly repairs in the future. 

A lightning strike or tornado can open up a masonry chimney, making it vulnerable to attack by rain.  Once a cement crown or bricks have been blown out or severely cracked, the interior of the chimney is open to the elements.  Rain can wash out mortar joints, cause damage to a fireplace, damper, and any metal or masonry components.  When mixed with creosote, rain forms an acid that eats away at mortar joints and flue tiles.

Water can enter through any interior open areas in the chimney, which may include the attic or other areas of the home. This can cause damage to drywall, wood framing, lighting, or carpet. 

A chimney fire can cause expansion of the masonry, which often forms cracks along mortar joints in exterior bricks, and occasionally through the bricks themselves.  This type of damage usually occurs at or near the top of the chimney, but may happen anywhere.  Expansion breaks sometimes occur when a chimney is rapidly heated during a chimney fire.  Any cracks or breaks in masonry will allow damaging rain water to enter the interior and cause further damage to the structure. 

After a lightning strike, high wind, or chimney fire it is important to have a Level II camera inspection completed by a professional chimney sweep, who will determine if damage has occurred to the internal structure of the chimney.  If this inspection is not adequate, a Level III inspection may be necessary.  This involves demolition of parts of the chimney in order to view the interior.

Manufactured chimneys should be inspected following a chimney fire or storm in order to determine if the metal chimney, fireplace components, or exterior chase, chase top, or cap has been damaged.  Manufactured chimneys are U.L. Listed products and parts must be replaced with parts for the specific model by the manufacturer.  Parts are not interchangeable.  If left un-repaired, a damaged manufactured wood chimney chase or metal components may be further damaged by the elements.

Repairs should be completed by a qualified professional chimney contractor in order to assure that the work is done according to International Residential Code and NFPA 211 Standards.  

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Marge Padgitt is the publisher of Wood-Fired Magazine, and an industry writer. She has been in the chimney industry since 1985. Websites: www.chimkc.com and www.woodfiredmag.com