Your Firebox and When It Needs Repair

Your firebox is the part of your fireplace that most commonly needs repair, and that generally happens every five to ten years. It needs repair when there are cracks in the protective wall it provides between fire and the structure of your home. It needs repair in other cases, too, and they are easiest to understand after a quick review of “fireplaces”.

Understanding the various parts of your chimney and how to keep them in good repair is critical. Annual inspections can identify problems early on.

Understanding the various parts of your chimney and how to keep them in good repair is critical. Annual inspections can identify problems early on.

Basic Ins and Outs of Firebox Repair

Working inward from your usual point of view, masonry fireplaces consist of:

  • the outer hearth
  • the mantel and fireplace face
  • the inner hearth and firebox
    • ash dump door, dump, and pit
    • throat, damper, and lintel
    • firebrick
  • the clean-out door, foundation, and footing

Seen that way, seeing just how much of the fireplace is in-above-and-below the firebox, it is not surprising that it is ‘the part’ that is most likely to need repair. Pre-fabricated fireplaces have fewer parts but they are more likely to need complete replacement. No less a problem than in firebrick, when cracks form in refractory panels, a pre-fab firebox also needs “repair”.

When the cracks are minor in either type of firebox, so are the repairs. Both can be patched with refractory mortars. However, when refractory panels are badly cracked, they need to be replaced. This, too, is fairly ‘easy’ but again requires lots of time and attentiveness to detail. When the same degree of cracking occurs in masonry fireboxes, ‘repair ‘is far more complicated and always best left to certified fireplace professionals.

Dampers

The damper is the other ‘part of the firebox’ that most commonly needs repair, usually due to dirt or rust, or both. Even cleaning a stuck damper is hard work and the best solution for a rusted damper usually is not in the throat at all. Your best bet for that “repair” is to add a top-mounted damper. It also doubles as a chimney cap when the firebox is not in use.