What is Creosote?

Nov 10, 2023

What is Creosote?

Creosote is a sticky, highly flammable substance that is a natural byproduct of chimney smoke. Creosote builds up inside of chimneys over time.

What Does Creosote Buildup In a Chimney Look Like (Stages Of Creosote)

Stage 1 Creosote Buildup

Stage 1 creosote buildup is flaky and powdery and is similar in appearance to coffee grounds. This is the normal stage of creosote buildup. It is flammable and therefore it is important to regularly remove it from your chimney. When the temperature gets hot enough while burning a fire, gasses release from the burning wood and condense on the cold surfaces of your chimney, resulting in the creosote buildup.

Stage 2 Creosote Buildup

The second stage of creosote buildup is characterized by a high concentration of thick tar and is highly flammable. This level of buildup significantly increases your risk of a chimney fire.

Stage 3 Creosote Buildup

This is the last and most dangerous stage of creosote buildup and it is not removable. At this point, the creosote is hard and shiny and can easily ignite, leading to a chimney fire. You should hire a professional to remove the normal creosote before it gets to this point.

What Are The Risks Of Creosote Buildup In The Flue?

As explained earlier, normal creosote buildup is flammable but it can be cleaned by a professional. However, if the creosote reaches Stage 2 or 3, it becomes a serious fire hazard.

The Solutions for Creosote Buildup

Prevention: Regular annual cleaning of your chimney can prevent the build up of creosote before it becomes a serious fire hazard.

Frequent Cleaning: If your chimney has already reached Stage 2 or Stage 3 creosote build up and you use your fireplace several times per week during the cold weather, it is advisable to either cease use of the chimney or to have it frequently cleaned. This could be done at the start of the burning season and mid the burning season to ensure your chimney does not accumulate more flammable creosote.

Install a New Liner in the Chimney: Some homeowners choose to have the chimney relined with a stainless steel liner and this is a surefire way of reducing fire risk.

Install a Gas Insert with Liner: A common solution for a chimney that is unusable due to creosote buildup is to install a gas insert into the fireplace. These units have their own liners and can be a safe solution for homeowners who have Stage 3 Creosote buildup.

Chemical Cleaning: Chemicals can be used to decrease the creosote buildup and it does help but its not a surefire method for handling creosote build up and frequent cleanings would still be required to keep it safe. The chemical process usually takes about 3 hours to apply, then it sits for 2 weeks and is swept. After this process, frequent cleanings will be required to keep it from building up again.

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.