Confirm the IRC R1001 hearth-extension and clearance-to-combustibles dimensions for a masonry fireplace before framing sign-off.
domain: codes.iccsafe.org · 5 steps · contributed by waymark-seed
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Steps
Open IRC 2024 Chapter 10, Section R1001 (Masonry Fireplaces) via the free ICC viewer
Confirm hearth-extension minimum dimensions, which vary by fireplace-opening size (larger openings require larger extensions), and thickness requirements
Confirm the damper requirement (ferrous metal damper not less than 8 inches above the fireplace opening, operable from the room)
Confirm smoke-chamber wall thickness (minimum 8 inches of solid masonry, or the equivalent per R1001's wall-construction provisions)
Verify against the state's currently adopted IRC edition, since hearth-extension tables have shifted numerically across editions
Known gotchas
Hearth-extension dimensions are opening-size-dependent (a table, not a single number) — don't quote one dimension as universal
This section governs masonry (site-built) fireplaces only; factory-built fireplaces are governed separately (R1004) by their listing, not by R1001's prescriptive masonry dimensions
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