What Is Parging a Chimney? How It’s Done and Why It’s Necessary

From the outside, chimneys appear as simple rectangles that allow smoke to pass through. But behind those brick facades lie numerous intricate parts that must all work in harmony for fireplaces and chimneys to operate properly and safely. One important part of chimney maintenance is parging. But exactly what is parging a chimney, and how do you know if your chimney needs it? This guide will walk you through all the details.

What Is Chimney Parging?

Parging is a masonry technique that involves smoothing out rough or cracked surfaces, usually by adding a layer of mortar. It’s done in a few different places around the home, including foundations and basement walls. When it comes to chimneys, parging is specifically done in the smoke chamber—an area above the fireplace and below the chimney flue. In fact, the process is often referred to as “smoke chamber parging” instead of “chimney parging.” Smoke chambers help smoke move up the chimney rather than getting trapped or, worse, pouring back out of your fireplace and into your house. Parging is typically done when a chimney is constructed, but older chimneys may need to be parged again due to wear and tear.

What Are the Benefits of Parging a Chimney?

There are several reasons to parge a chimney’s smoke chamber, and there are no real drawbacks aside from the cost. Here are the main benefits:

Safety

First and foremost, parging makes chimneys and fireplaces safer. It reduces the likelihood of chimney fires and back-drafting, and it helps hazardous gasses like carbon monoxide exit the chimney safely. 

Energy Efficiency

A smooth and sealed smoke chamber creates better insulation and allows for a natural draft, both of which help fireplaces burn hotter and longer. One of the major indicators that your chimney needs to be parged is if you have a hard time starting a fire or keeping it lit. You’ll also notice that your house heats up faster after the chimney is parged.

Longevity

Parging improves a chimney’s structural integrity and cuts down on creosote buildup. Creosote—a black, sticky compound that results from wood combustion—can cause chimney fires. All chimneys accumulate creosote over time (which is why routine professional chimney cleaning is recommended), but a chimney in need of parging may accumulate creosote more quickly. 

Code Compliance

In most places, smoke chambers are legally required to be parged for safety reasons. That’s why parging is done early on when a chimney is being built. Smoke chambers with large cracks and jagged surfaces likely aren’t up to code.

How to Parge a Chimney

Photo: Bill Oxford / iStock / Getty Images Plus / Getty Images

There are two ways to parge a chimney’s smoke chamber, both of which are usually done by a local chimney repair technician:

1. Cast-in-place: This is the most common way to parge a chimney, and it consists of spreading mortar inside a smoke chamber with a hand trowel until the surface is perfectly smooth. It’s usually how the bricks or stones used to make a masonry chimney are parged in the first place during installation.

2. Spray-on: As an alternative, some chimney technicians use a pressurized spray of mortar or cement to parge a smoke chamber’s surface. It’s quicker than the cast-in-place method but still effective.  

Should I DIY or Hire a Pro?

Parging is safer and easier than several other types of chimney repairs–like chimney repointing, for example–but hiring a local pro is usually better than attempting the job yourself unless you have pertinent experience. A major reason is that parging an old chimney usually requires sections to be removed and reinstalled. Unfortunately, that also makes parging an expensive repair. On average, it costs between $1,000 and $2,000 to parge a chimney.

Does My Chimney Need to Be Parged?

If you’re installing a new chimney, the smoke chamber should be parged during construction. It’s harder to tell when it comes to an old chimney. A surefire way to know that your chimney needs to be parged is by contacting a chimney inspector in your area to take a look. They can diagnose present or future issues with the smoke chamber, as well as other issues with your chimney. A few signs that it’s time to call an inspector include:

• Excess smoke coming from the fireplace

• Difficulty starting a fire or keeping it lit

• An odd, tar-like smell when you use the fireplace

• Noticeable cracks or brick remnants in the fireplace