Chimney and Fireplace Anatomy

Know the Protective Components of Your Chimney

chimney cap installation gaithersburg mdAs solidly built as chimneys are, they need a number of components to keep them working safely and efficiently. Let’s look at some of these chimney components and find out what they do and why it’s important.

Chimney flue

The flue, often just called the “chimney,” is the vertical interior passage that allows smoke to move up and away from the fireplace. A sturdy flue serves as a protector for nearby combustible materials of the home by containing intense heat and toxic gasses.

Flues are commonly constructed of brick and mortar (masonry) and hold up well for many years. Eventually, however, cracks in the masonry can begin letting water into the system, where it will start a cycle of decay until the flue is no longer safe to operate. Leaky chimneys need prompt professional attention.

Chimney liner

Chimney liners are built or installed on the inside of the flue to add even more protection to the home. Liners can be made of metal, clay tiles or a poured-in-place compound. As with the chimney’s masonry, if cracks appear in the liner, heat and gasses can escape and cause damage.

Assessing the condition of a chimney liner normally requires the services of a certified chimney inspector, who will use various tools including video technology to look at all the surfaces of the liner.

Roof flashing

Flashing is the metal strips that block the gap between the external chimney masonry and the roof. Without a layer of flashing, rainwater and water from melting snow can run down into the home and cause rotting and decay to walls, insulation and other structural components.

Incoming water also can begin to harm the exterior masonry of the chimney in areas the average person can’t see. Flashing is one of the easiest ways to prevent some very expensive damage.

Chimney crown

The chimney crown is the cement layer that seals off everything at the top of the chimney except for the flue pipes. Like the chimney cap, the crown shields the flue from water and moisture. Crowns usually are beveled to allow water to run away from the flue opening.

Cracks in chimney crowns can happen after years of use. If caught early, the cracks can be sealed to prevent further damage. In some cases, a crown will have to be rebuilt.


Located just above the firebox, the damper is open when a fire is burning to allow a smooth path for smoke and toxins to leave the home. A damper that won’t fully open can cause smoke and dangerous carbon monoxide to back up into the home.

After many years of service, dampers can become rusted and warped, making it impossible to close them completely when the fireplace isn’t in use. Damaged dampers can be repaired or replaced.

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Chimney cap

The chimney cap sits atop the chimney and provides protection against incoming rain and snow as well as debris such as leaves, twigs and small-animal nests.

A good chimney cap also acts as a barrier to keep shooting sparks and embers from flying out the top of the chimney and landing on the roof or in the yard. Damaged chimney caps can either be replaced or repaired.

High’s Chimney Service of Gaithersburg, MD, is here to help keep all your chimney components and your chimney itself in excellent working condition. We provide a full menu of chimney cleaning, chimney repair, component installation and chimney inspection services. Learn more or schedule an appointment by calling (301) 519-3500.

Damaged Chimney Signs & Symptoms

Chimney Masonry Repair in Fulton MDA fully functional chimney is a safe chimney. A damaged chimney can be dangerous. Fortunately, you can spot many signs of chimney damage and arrange for the necessary repairs before the problem gets out of hand. Here are four areas of chimney damage/chimney issues to be on the lookout for.

Leaky chimney signs

Water in the firebox: If you see water inside your firebox, likely it means there’s a leak somewhere in the system.


White stains on masonry: White stains (efflorescence) are caused by naturally occurring salt and mean that water is getting into the masonry.

Foul smells coming from the fireplace: Excess moisture inside the flue often is caused by a leaky chimney. Moisture mixes with soot and creosote and produces strong odors.

Structural damage 

Crumbling on the roof: Masonry damage often leaves areas of crumbling on the roof near the base of the chimney.

Leaning chimney: If a chimney has begun to lean to one side, it indicates a significant level of damage that needs to be addressed before using the fireplace again.

Missing bricks: When bricks fall completely away from the chimney or parts of the bricks are missing, water damage is often the reason.

Black staining at the top of the chimney: This could be caused by the excess, thick smoke produced by a chimney fire.

Damage to chimney components

Damaged chimney cap: Any compromise to the vented areas of a chimney cap mean that unwanted obstructions could get into the flue and cause drafting issues.

Cracks in the chimney crown: Crown damage commonly begins with small cracks, which expand over time due to freeze-thaw cycles. Water inside the crown structure eventually can destroy it.

Flashing problems: The flashing that blocks the gap between the chimney and the roof should be flat and secure in order to keep water from running down into the home. Warped or deteriorated flashing needs to be replaced.

Chimney liner damage: If the chimney liner begins to break apart or degenerate, you may notice pieces of it in the firebox. You also may be able to visually see some parts of the liner to determine if damage is present.

Chimney Flue Cleaning in Glenwood, MDIssues inside the flue

Aside from what’s listed above, two serious issues can take place inside the flue.

  1. Excess creosote buildup: Creosote is formed when wood burns. The substance is flammable and responsible for most chimney fires in the U.S. each year.
  2. Outside obstructions: Things such as small-animal nests, dead small animals, leaves, twigs and other debris can narrow the smoke passage and cause smoke and carbon monoxide to back up into the house. In both these cases, professional chimney sweep services are called for.

As a homeowner, you can keep a close eye on your chimney and its components and be able to tell when something is wrong. However, your “novice” inspections are no replacement for professional chimney inspections performed by certified technicians. If you watch your chimney and schedule annual inspections by a pro, you’ll be taking a big step toward keeping your chimney safe and running optimallyHigh’s Chimney Service of Gaithersburg, MD, provides everything you need for a safe chimney including certified chimney sweep, professional inspection and expert repair services. Call (301) 519-3500 with questions or to schedule an appointment.