Guide to the Anatomy of a Chimney

May 31, 2024

Towering above rooftops, chimneys are iconic architectural features that often go unnoticed and underappreciated. But these structures play an important role in allowing fires to breathe and buildings to vent out harmful gases safely. More than just decorative facades, chimneys contain an ingenious network of components working together in systematic harmony.

From the visible outer stack to the hidden inner liner, a chimney’s anatomy is an engineering marvel designed to maximize airflow and withstand intense heat. So next time you spot a chimney, pause to admire the hero protecting the household by removing combustion’s unwanted byproducts.

Now, let’s explore the different parts that make up a chimney.

The Chimney’s Main Sections

At its most basic, a chimney consists of the following primary sections:

The Chimney Stack

The most visible part is the chimney stack, the vertical tower rising above the rooftop. It’s usually made of bricks, concrete blocks, or an insulated metal pipe. The stack protects the inner flue from weather while providing an exit path for exhaust.

The Flue Liner

Running down through the center of the stack is the flue liner. This hollow channel, called the flue, is where the hot gases and smoke travel upward. Flue liners are constructed from fired clay tiles, or a poured refractory cement, or an insulated stainless-steel pipe. Their smooth interior helps establish good air draft while containing the high heat.

The Smoke Chamber

At the bottom of the flue is the smoke chamber, a space that collects combustion gases from the firebox. This transitional area allows the smoke to shift direction into the vertical flue above. Dampers are located here to regulate airflow and prevent air drafts when not in use.

The Chimney Crown

At the very top is the chimney crown. This concrete slab or metal pan covers the chimney stack, shielding the interior from rain. It usually overhangs slightly beyond the stack to allow precipitation to drain away.

Other Key Components

Every chimney should also include:

  • Chimney Cap/Spark Arrester: A cover and  screen on top to keep out water, animals, debris, and downdrafts.
  • Flashing: Sheet metal strips sealing gaps between chimney and roof.
  • Firestop: Heat-resistant barriers in framed spaces the chimney passes through.

All these different parts work together as a system to safely vent dangerous gases and smoke away from the building interior.

Staying Safe with Chimneys

To keep chimneys functioning properly and avoid fire hazards:

  • Have chimneys inspected and swept annually by professionals.
  • Check regularly for cracked or deteriorated mortar, tiles, or liners.
  • Install chimney caps and screens to block debris and animals.
  • Burn only approved materials like dry wood, never trash or chemicals.
  • Never overfire beyond designed temperature or draft ratings.

By understanding a chimney’s anatomy, you can better maintain this essential venting system and keep your home safe season after season!

Ready to ensure your chimney is in excellent condition? Trust Chimney Clean Company, Inc. for cleaning, inspecting, and repairing chimneys and fireplaces in Santa Clara County and the South Bay Area. Whether it’s a minor repair or a major rebuild, we’ve got you covered. Don’t wait until it’s too late—contact us today to schedule your chimney service!

Smoking back

There are many fireplaces that seem to smoke back into the house no matter what is done. In our experience, the most common cause is that the fireplace simply needs to be cleaned. This is especially likely if the fireplace has gotten worse over time, that is, the smoking back is worse now than it used to be.

Several other possible causes of smoking back are problems with the damper, chimney cap, grate, firewood, or structural problems with the chimney itself. At Chimney Clean Company, we do a full inspection with every cleaning, or we can also do just the inspection if the chimney doesn’t need to be cleaned. This inspection is designed to reveal any causes of smoking back.

Broken chimneys

In the Bay Area, many chimneys were broken in the 1989 Loma Prieta earthquake. Usually, these chimneys are broken at or near the roof line, although sometimes they can be broken further down, even at the ground level.

We are fully licensed masonry contractors. We rebuild broken chimneys. If they are broken at the roof line, this usually entails taking the chimney part of the way down brick by brick, installing steel reinforcing bars, getting an inspection from a city inspector, then rebuilding the chimney back up around the steel rebar.

Missing mortar or damaged bricks

Over time, many chimneys develop places that are missing mortar between bricks, or damaged bricks, either inside the firebox or on the outside of the chimney. These areas can usually be repaired, either by replacing the missing mortar or replacing the bricks themselves. Items such as these can be dangerous because they can allow flames, sparks or hot gases to enter the structure of the house.

Water entry

Sometimes the metal that seals the chimney at the roof, called “flashing”, will come loose or develop leaks. In this case, water sometimes comes into the ceiling of the room and causes water spots and stains on the sheet rock. This flashing should be repaired before the water causes more damage.