Water and masonry chimneys are natural enemies. A masonry chimney is made of bricks and other materials can get damaged by water intrusion. It is built using a combination of materials such as concrete, stone, steel, and cast iron, among others. Water can harm most of the materials used in building the chimney. So it’s important to take steps to prevent water from getting inside.
All masonry chimney construction materials, except stone, 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.
Note: While most stone is not affected by water penetration, large amounts of mortar are required to bond the stone together properly. Therefore, a stone chimney – just like a brick chimney – should be protected from the effects of water penetration.
Water penetration can cause interior and exterior damage to your home and masonry chimney including:
• Rusted damper assemblies
• Deteriorated metal or masonry firebox assemblies
• Rusted fireplace accessories and glass doors
• Rotting adjacent wood and ruined wall coverings
• Water stained walls and ceiling
• Clogged clean out area
• Deteriorated central heating system
• Stained chimney exterior
• Decayed exterior mortar
• Cracked or deteriorated flue lining system
• Collapsed hearth support
• Tilted or collapsed chimney structure
• Chimney settlement
In addition, when water mixes with creosote in a wood-burning chimney system, it will generate a highly disagreeable odor that can permeate a home. Ultimately, water and masonry chimneys just don’t mix.
Rain covers, also known as chimney caps, are a simple and affordable solution for homeowners to keep water from seeping into their chimneys and causing damage. Chimney caps are an important safety feature that can prevent costly repairs. Underwriters Laboratories (UL) requires a chimney cap to be included in any chimney lining system that meets their testing standards.
Chimneys have one or more large openings (flues) at the top that can collect rainwater and funnel it directly to the chimney interior. A commonly-sized flue has the potential to allow large amounts of rain or snow into the chimney during just one winter when freeze/thaw cycles are common.
Chimney caps also provide other benefits. A strong, well-designed cap will prevent birds and animals from entering and nesting in the chimney. Caps also function as spark arrestors, preventing sparks from landing on the roof or other nearby combustible material.
A chimney cap should be easily removable to facilitate inspection and cleaning. For a long and effective service lifetime, a cap should be constructed of sturdy, durable, and corrosion-resistant material. Caps may be designed to cover a single flue, multiple flues, a large portion of the chimney, or the entire chimney top. A full-coverage chimney cap usually represents a larger initial investment. However, it is probably the best investment for long-term protection because of its ability to protect the entire chimney and crown.