The most common repair to your chimney’s smoke chamber — which serves to funnel smoke from the fireplace opening into the flue — is parging.

Parging is a coating of mortar applied to the brick to give the smoke chamber a smooth surface. Learning to parge is not part of the requirements of earning a certification from Chimney Safety Institute of America, but it is taught at CSIA’s National Chimney Sweep Training School. [Learn what’s offered in the daily program here.] During a chimney fire, the parging is often cracked and damaged.

MORE: What does parging a smoke chamber look like? Watch our video, featuring CSIA instructors Michael Segerstrom and Bob Fish.

According to [CSIA Education Director] Ashley Eldridge and [CSIA Instructor] Jim Brewer’s book, “The Homeowner’s Guide to Chimney, Fireplaces and Wood Stoves,” improper design of the smoke chamber can lead to numerous problems. The smoke chamber can be too deep, too tall, or too wide. In some cases there is a void in the smoke chamber that needs to be sealed.  Air moving into the chimney will have the effect of reducing the draft.

It may also be extremely rough and irregular in construction. NFPA 211 (National Fire Protection Association’s standard for Chimneys, Fireplaces, Vents, and Solid Fuel Appliances) recommends that smoke chambers should not be taller than the fireplace opening width, nor deeper than the fireplace opening.

NFPA further states that the smoke chamber walls should not incline more than 45 degrees from vertical. The walls of the smoke chamber should be smooth to reduce turbulence. Most building codes require that smoke chamber walls be parged.  The flue should start at the top of the smoke chamber and should not have any radical offsets or bends. Corner fireplaces are a special problem here as the smoke chambers tend to be quite large and irregular. Most smoke chamber design problems are difficult to correct and will require specialized skills. But this service can be done — and often is — any time during the year.

“You are adding insulating quality to that smoke chamber,” said Bob Fish, a Londonderry, Vermont-based CSIA Certified Chimney Sweep since 1988. Bob is also a veteran instructor of the National Chimney Sweep Training School. “Therefore you are going to maintain more heat going into the flue, therefore you are going to have better draft in your system.”

MORE: To parge or not to parge? CSIA Certified Chimney Sweep Paul Bianco at Chimney Savers, Inc., in Vermont discusses.

National Chimney Sweep Training School and smoke chamber parging

Some parging material mixed on site.