A fireplace can be attractive and add value to a home. On that first winter evening that the new owners decide to light a fire to celebrate “hearth and home” and perhaps a little romance, if the fireplace smokes up the house, it can become a crisis. More than once I’ve been called in to address this source of the buyer’s anger and dissatisfaction.
As a matter of fact, about 50 percent of masonry fireplaces do smoke. I can assure you from my experience as a home inspector that a FIREPLACE SMOKES, IF..…….
- The interior brick or stone facing of the fireplace has been recently painted.
- The flue has been extended above the chimney masonry 2 or 3 feet.
- The flue has an architectural arch or other covering that prevents air from flowing over the top of the flue from one or two directions.
- There are trees overhanging the top of the chimney.
- The home sits below a close by hilltop, or
- The 3:2 ratio for the firebox opening is violated.
The ideal firebox opening for modern masonry fireplaces is 3’-0” wide by 2’-0” high, with a depth of about 1’-8”. The most common mistake made is allowing the height of the firebox to exceed the ratio.
Violating this ratio means that the fireplace illustrated in the first diagram smokes because it can’t help it. The design sizes dictate that it MUST smoke!
WHAT CAN BE DONE?
If you have a fireplace that smokes, here’s what you can do…..Simple to more complex fixes1
- Lower the height of the firebox opening by installing a 4 to 6 inch decorative piece across the top of the firebox just under the lintel. I’ve seen this done with both metal and ceramic pieces.
- Raise the height of the floor (or base) of the firebox by adding a layer of firebrick (about 3 inches), or using a “highboy” grate that sits about 8 inches above the base of the firebox, or both.
- Install glass doors, which often have a solid top of about 4 to 6 inches which, in effect, lowers the height of the firebox. In addition, the glass doors help contain the smoke within the firebox.
- If the inside of the flue area above the damper looks rough and irregular, have a chimney sweep re-parge the interior area above the damper and below the flue tile – a.k.a. The smoke shelf, (see diagram). Smoothing out the rough masonry will allow the smoke to more easily rise up the flue.
- If the chimney has a decorative architectural arch or cap over the flue at the top of the chimney, remove it.
- Extend the top (height) of the chimney flue 3 to 6 feet. If you extend the flue by adding flue tile, be sure to extend the masonry too, or provide some other means of support for the flue tile.
- Convert the fireplace to gas logs. This might be a desirable option anyway because in many jurisdictions wood burning fireplaces are being outlawed because of the pollutants they add to the air.