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Identifying the Reasons Behind Chimney Discoloration

As years and decades pass, chimney bricks often fade from the effects of blazing-hot sun. This is normal. Other types of chimney discoloration aren’t normal and may signal a need to address the problem immediately.

Various stains can appear on the exterior bricks of a chimney. Here are those that are most common, what they mean and what needs to be done about them.

White stains

Discolored masonry brickEvaporated water is the cause of white staining, or efflorescence, on your chimney. This may be nothing more than normal evaporation of rain, snow or ice. But it also can be a sign that water is getting into the bricks and mortar, which can lead to serious structural damage. Moisture trapped within the masonry also can encourage the growth of mold.

Green, blue and some black stains

These shades of discoloration on the surface of your chimney likely point to mold or algae. Both contaminants thrive on moist environments with little or no air circulation – such as inside cracks in the chimney’s masonry. Algae and mold, especially in large infestations, are known to present health risks to humans and animals.

Brown and some black stains

Brown and black (not mold) stains on a chimney, roof or exterior house walls can have several causes. The biggest concern is when the stains are caused by soot and creosote. When this happens, the reason they’re escaping the chimney needs to be identified quickly. In some cases, the root cause may be a problem with drafting inside the chimney. Another cause can be a chimney fire that burned and went out on its own before anyone was aware of it.

Rust stains

If there is rust on your chimney’s masonry, the most likely cause is corrosion and rusting on your chimney cap that is mixing with rain water. A damaged chimney cap eventually will allow water into the flue, where it will begin to erode sections of the chimney structure.

The value of professional chimney inspection and repair

While you may be able to spot signs of discoloration on your chimney, you probably don’t have the training or equipment necessary to resolve the problem safely and thoroughly. Certified chimney services professionals can diagnose the cause(s) of discoloration and quickly get to work to remedy the situation. For example:

Cracks in chimney masonry: First, we want to determine the location and extent of the damage. Then we can either seal coat the chimney or add fresh new mortar to open areas to prevent further water infiltration.

Mold or algae: If the growth of these contaminants originates from moisture being held in cracks in the masonry, we’ll get the problem fixed fast.

Soot Marks on Chimney MasonryCreosote & soot: We can remove these stains from the outside of your chimney and adjacent areas. We also can perform a thorough inspection to find out why these substances are exiting the chimney in the first place. After cleaning creosote and soot from the flue, we’ll be able to determine if a chimney fire has caused internal damage to the structure.

Rust: A damaged, rusted chimney cap needs to be replaced.

If you’re noticing discoloration on your chimney, the smartest move is to have one of our certified chimney technicians look at it. We’ll diagnose the problem and repair it properly and safely. To arrange an appointment or to get your questions answered, call Complete Chimneys of Pasadena, MD, at (410) 544-7600.

Why You Should Have Your Chimney Relined

A well-built chimney can withstand years of intense heat and toxic exhaust gasses and the damage both can  cause.  But even the best-made chimney won’t perform optimally forever.  This is why there are chimney liners.  Made from several different types of materials, chimney liners offer the added protection you need to extend the life of your chimney and avoid many of the repairs that otherwise would be inevitable once a chimney passes a certain age.

Chimney Relining in Annapolis MD

If you don’t have a chimney liner, consider installing one.  If you do have a liner, make sure to schedule yearly inspections with a certified chimney specialist to check for early signs of liner damage and get them fixed quickly.

Types of chimney liners

There are three main types of chimney liners:

  1. Clay tiles
  2. Metal
  3. Cast-in-place

Here’s a brief overview of each.

chimney repair in Russett MDClay tiles:

The most common chimney liner material, clay tiles are economical and generally perform well.  However, they’re not quick to absorb and distribute the rapidly rising temperatures in the event of a chimney fire, which can cause the tiles to crack and split and leave the chimney’s masonry vulnerable.


Metal chimney liners are typically made of aluminum or stainless steel.  Most often used as replacement liners for existing chimneys, these liners are highly durable when temperature insulation is included in the installation.  Metal liners are perfect for use with wood and gas fireplaces.

Cast-in-place chimney liners:

This style of liner is made from a poured cement-like product installed in the flue to provide a smooth, insulated path for heat and combustion gasses.  They add strength to the structural integrity of a chimney and can accommodate all fuel types.

Primary functions of chimney liners

The Chimney Safety Institute of America lists three primary jobs of a chimney liner:

1. Protect the building materials of the home proximal to the chimney.  When the fireplace is operating, intense heat travels up through the flue.  A quality chimney liner acts as a buffer to keep excess heat from harming parts of the home that surround the chimney.  Tests have shown that woodwork adjacent to an unlined chimney can catch fire in as little as three and a half hours.

2. Protect the chimney’s masonry from heat, moisture and combustion byproducts.  As strong as chimney bricks and mortar are, they eventually will deteriorate after years of intense heat, moisture and gasses.  A chimney liner protects against this deterioration, which can damage a chimney to the point the entire structure must be rebuilt.

3. Create a properly sized flue.  In order for fireplaces to operate at maximum efficiency, the right flue size is required.  Smoke and gasses must exit the fireplace system at a specific pace to avoid excess creosote buildup from wood-burning appliances and the creation of excess carbon monoxide from gas units.  Flue size in relation to fireplace output also affects drafting and burn-efficiency.

If it’s time to have your chimney liner inspected or repaired, Complete Chimneys of Pasadena, MD, is ready to help.  Need a new chimney liner installed?  Our certified chimney technicians will get it done safely and quickly.  Call (410) 544-7600 with questions or to arrange an appointment.