Short answer
For a masonry fireplace, Florida’s residential code keeps combustible trim and mantels at least 6 inches from the opening and limits how far they project within 12 inches of it, and it sets minimum hearth extension sizes. Factory-built fireplaces, gas units and inserts follow the clearances in their own installation manuals, which can be stricter or looser.
Masonry fireplaces: the code minimums
For masonry fireplaces, the Florida Building Code, Residential sets out clearances in its chapter on chimneys and fireplaces (UpCodes, Chapter 10). The main numbers homeowners run into are summarized below; the code has more detail and exceptions.
| Item | Requirement |
|---|---|
| Combustible trim or mantel near the opening | Not within 6 inches of the fireplace opening |
| Combustible material within 12 inches of the opening | May not project more than 1/8 inch for each 1 inch of distance from the opening |
| Hearth extension, opening under 6 sq ft | At least 16 inches in front of the opening and 8 inches beyond each side |
| Hearth extension, opening 6 sq ft or larger | At least 20 inches in front and 12 inches beyond each side |
In practice, the projection rule means a mantel shelf that sticks out several inches has to sit well above the opening. A shelf projecting 8 inches, for example, can’t be within 12 inches of the opening at that depth, because 8 inches of projection would need 64 inches of distance under the 1/8-inch rule. It has to sit at least 12 inches above, where the 12-inch rule no longer applies.
Masonry chimney and fireplace, cutaway
- 1Chimney cap. Metal lid with mesh sides over the flue opening. Keeps rain, debris and animals out.
- 2Crown. The concrete or mortar top of the masonry, sloped to shed water away from the flue.
- 3Flue liner. Clay tile or metal lining that carries smoke up and protects the masonry from heat.
- 4Flashing. Metal that seals the joint between the chimney and the roof.
- 5Brick & mortar. The chimney structure. Mortar joints and brick faces absorb water when they wear.
- 6Smoke chamber. The sloped transition that funnels smoke from the firebox into the flue.
- 7Damper. Metal plate at the throat (or a sealing lid on top) that closes the flue when not in use.
- 8Firebox. Where the fire burns. Firebrick laid in heat-resistant mortar.
- 9Hearth. Non-combustible floor extension in front of the fireplace opening.
Factory-built and gas fireplaces: follow the listing
Factory-built fireplaces, gas fireplaces and inserts have clearances set by their manufacturers and tested as part of their listing. They appear in the installation manual, often as diagrams showing mantel height versus depth, side wall distances and hearth requirements. Those numbers can be stricter or looser than the masonry code, and they are what an inspector checks. The model number on the rating plate finds the manual.
Common remodel mistakes
- Adding a deeper wood mantel shelf without checking the height against the projection rule or the manual.
- Wrapping a surround in wood or other combustible trim right up to the opening.
- Mounting a TV directly above a fireplace without checking the manufacturer’s limits. Heat can damage electronics and some manuals restrict it.
- Covering a hearth extension with combustible flooring, or shrinking it during a flooring job.
- Replacing a factory-built unit’s surround with materials the manual doesn’t allow.
Everyday clearance habits
- Keep rugs, furniture, stockings and decorations at least three feet from an open fire, and follow the manual for gas units. The USFA fireplace safety card gives the same three-foot guidance.
- Use a screen or doors on wood fires.
- Keep children back from gas fireplace glass, which gets very hot; see cracked fireplace glass.
If you’re remodeling around a fireplace, or buying a home where the surround has been changed, a fireplace inspection checks the clearances against the code or the listing. Surround and hearth work is part of fireplace restoration.
Clearances are one part of a safe setup; fireplace carbon monoxide and is my fireplace safe to use cover the others. If you are planning an insert, fireplace inserts explained covers its hearth and surround requirements. For remodel questions in older homes, see fireplace repair in Maitland.
References (2)
Facts and figures on this page come from these references.
