Water Damage and Your Masonry Chimney

As odd as it may seem, water causes more damage to masonry chimneys than fire.

Think about it for a moment. All the brick and other materials that make up your home are protected by the roof and eave, all that is, except your chimney. The chimney bravely sticks up above the roof constantly exposed to all the elements; rain, snow, and freeze/thaw cycles.

A masonry chimney is constructed of a variety of masonry and metal materials, including brick, mortar, tile, steel and cast iron. All of these materials will suffer accelerated deterioration as a result of prolonged contact with water.

Masonry materials deteriorate quickly when exposed to the freeze/thaw process in which moisture that has penetrated the materials periodically freezes and expands, causing undue stress. Water in the chimney also causes rust in steel and cast iron, weakening or destroying the metal parts.

Water penetration can cause interior and exterior damage to your home and masonry chimney including:

• Spalled and broken brick
• Deteriorated metal or masonry firebox assemblies
• Rusted damper assemblies
• Rotted adjacent wood and ruined wall coverings
• Deteriorated central heating systems
• Decayed mortar
• Cracked ceramic flue liner systems

Preventing Water Damage

• Install a Chimney Cap
• The most inexpensive preventive measure that a homeowner can employ to prevent water penetration and damage to the chimney. A cap will also prevent birds and animals from entering and nesting in the chimney. They also function as spark arrestors , preventing sparks from landing on the roof.
• Repair or replace a damaged chimney crown
• The chimney crown, or also called the chimney wash, covers and seals the top of the chimney. Many of the chimney crowns deteriorate, chip, and crack allowing for weather to enter the interior portion of the chimney.
• Repair or replace flashing
• The flashing is the seal between the roofing material and the chimney. Flashing prevents rain water from running down the chimney into the living spaces where it can damage ceilings and walls, or cause rot in rafters, joists, or other structural elements.
• Waterproof your chimney
• Masonry material is porous and will absorb large amounts of water. Waterproofing your chimney will allow for the chimney to breathe out, but not in. Water that has penetrated the chimney or moisture that has originated from inside is allowed to escape, while the waterproofing agent prevents water from entering from the outside.

Water damage to masonry chimneys is usually a slow, subtle process. The problem is often not evident until it has become quite serious.

Although water prevention measures may cost a few dollars initially, they will save you the major expense of large masonry repairs or rebuilding of the entire chimney.