IRC Chapter 10 · 2021 R1001.11 · Fireplace clearance
Fireplace Clearance to Combustibles
The general 2021 IRC rule keeps wood framing and other combustible material at least 2 inches from the front and sides of a masonry fireplace, and at least 4 inches from its back. Mantels, trim and certain other conditions have specific exceptions—not blanket permission to put wood against masonry.
Keep the clearance airspace open
The general clearance applies to wood beams, joists, studs and other combustible materials around the masonry fireplace. The required airspace is not to be filled, except for fireblocking as addressed by Section R1001.12. Filling a gap with insulation is not a substitute for maintaining clearance.
The four fireplace clearance exceptions
1. Listed and labeled fireplaces complying with UL 127 may permit combustible material in contact with their exterior surfaces. The listing is essential; this does not apply to every fireplace.
2. Where the fireplace forms part of a masonry or concrete wall, combustible material must not contact that wall less than 12 inches from the inside surface of the nearest firebox lining.
3. Exposed combustible trim and the edges of sheathing materials may abut the masonry fireplace sidewalls and hearth extension as shown in Figure R1001.11, provided they are at least 12 inches from the inside surface of the nearest firebox lining.
4. Exposed combustible mantels and trim may be placed on the fireplace front, but not within 6 inches of the fireplace opening. Material within 12 inches of the opening is limited to a projection of 1/8 inch for each 1 inch of distance from the opening.
Mantel distance and projection work together
The front-face exception is not just a minimum-distance rule: the depth of projecting combustible material matters too. Do not confuse the distance from the fireplace opening with the inside surface of the firebox lining used in other exceptions.
For example, at 8 inches from the opening, the stated projection limit is 1 inch. A deeper mantel requires a different placement and review of the applicable requirements.
Check before remodeling
A new surround, mantel or wall finish can conceal combustible framing or reduce an existing clearance. Masonry fireplace clearance, masonry chimney clearance and factory-built fireplace installation are different checks. Have the actual assembly reviewed before making changes.
Check the requirements for your fireplace
These explanations concern masonry fireplaces and chimneys. Listed factory-built systems have their own listing and manufacturer’s installation requirements. Your building department determines the applicable code edition and any local requirements; this guide is not a permit approval or a substitute for an inspection.
Read the ICC Chapter 10 referenceChimney and fireplace help in northern Illinois
If you are planning fireplace changes or concerned about the chimney liner, chimney height, combustible framing or the smoke chamber, arrange an inspection. After cleaning, we visually inspect for imperfections and quote any needed repairs afterward, in writing or verbally, before repair work begins.