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ReferenceWood Stove Code Glossary
Plain-English definitions of every code term you'll encounter when researching wood stove installation, permits, and inspections.
Class A Chimney
A factory-built metal chimney listed to UL Standard 103 HT (High Temperature). Class A chimney is the only type approved for wood-burning appliances. It consists of stainless steel inner and outer walls with insulation between them, designed to maintain safe surface temperatures while containing hot flue gases. Required for all sections that pass through walls, ceilings, attics, and roof assemblies. Sometimes called "all-fuel" chimney.
Clearance
The minimum distance required between a heat-producing appliance (or its connectors) and combustible materials such as wood framing, drywall, flooring, and furniture. Clearances are listed on the appliance's certification label and may be reduced by installing approved heat shields. The purpose of a clearance is to prevent the surface temperature of combustible materials from reaching a level that could cause ignition over time.
Combustible
Any material that can catch fire. In wood stove installation, combustibles include wood framing, plywood subfloor, OSB sheathing, drywall (paper facing), hardwood floors, carpet, vinyl, insulation with paper facing, and most trim materials. Non-combustibles include concrete, brick, stone, ceramic tile (when properly installed on non-combustible substrate), steel, and listed hearth pad assemblies.
CSIA (Chimney Safety Institute of America)
The national certification organization for chimney sweeps and inspectors. CSIA Certified Chimney Sweeps (CCS) have passed a national examination and demonstrated knowledge of chimney safety, codes, and inspection procedures. When selecting a chimney professional, look for CSIA certification. NFI (National Fireplace Institute) is a related certification for hearth product professionals.
EPA Phase 2 Certification
The current EPA standard for wood-burning heaters, effective May 15, 2020. Requires wood stoves, inserts, and other wood heaters to emit no more than 2.0 grams of particulate matter per hour (g/hr). Stoves certified under the earlier Phase 1 standard (4.5 g/hr non-catalytic / 7.5 g/hr catalytic) cannot be sold new or installed with a new permit in most jurisdictions. See the EPA Certification Guide for details.
Hearth Extension (Hearth Pad)
The non-combustible floor protection required under and in front of a wood stove. Sized based on the firebox opening area: minimum 16 inches in front and 8 inches on sides/rear for openings under 6 sq ft. Must be made of non-combustible materials — listed hearth pads, masonry, or properly assembled tile-over-cement-board systems. See Hearth Pad Requirements.
IRC (International Residential Code)
The model building code published by the International Code Council (ICC) and adopted (with local amendments) by most U.S. states as the basis for residential construction requirements. Chapter 10 of the IRC covers chimneys and fireplaces. Section R1004 specifically governs factory-built fireplaces and solid fuel appliances including wood stoves. Most state codes reference the IRC edition they've adopted — commonly 2018 or 2021.
Level 2 Chimney Inspection
A comprehensive chimney inspection per NFPA 211 that includes a video scan of the interior flue. Required (per NFPA 211 recommendations) whenever an appliance is changed, after any chimney fire, or when a home changes ownership. A Level 2 inspection identifies cracks, liner deterioration, obstructions, and clearance violations that visual inspection alone cannot detect. Cost: typically $200–$400 from a CSIA-certified inspector.
Listed / Listing
A product that has been tested by a recognized testing laboratory (such as UL, ETL, or CSA) and found to meet applicable safety standards. "Listed" does not mean "approved by a government agency" — it means a private testing lab has verified the product meets published standards. Building codes require listed products for chimneys (UL 103 HT), stovepipes, and hearth pads. Mixing components from different listed systems (e.g., one brand's pipe with another brand's support box) voids the listing.
NFPA 211
The National Fire Protection Association's Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances. The authoritative technical standard for chimney systems and solid fuel appliance installation in the United States. The IRC references NFPA 211 for technical details on chimney sizing, clearance reductions, chimney height rules, and inspection levels. The current edition referenced in most adopted codes is the 2019 or 2021 edition.
Single-Wall Stovepipe
The black metal connector pipe used between a wood stove's flue outlet and the chimney system. Single-wall stovepipe requires 18 inches of clearance from all combustible surfaces and cannot be used through walls, ceilings, floors, or attic spaces. Contrasted with double-wall stovepipe (6-inch clearance) and Class A chimney (2-inch clearance through building assemblies).
Stovepipe (Connector)
The section of pipe connecting the stove's flue outlet to the chimney system. Different from the chimney itself — the stovepipe is the short connector section, subject to different clearance rules than Class A chimney pipe. Joints in single-wall stovepipe must be oriented with the crimped (male) end down, overlapping the smooth (female) end above, to prevent creosote from leaking out of joints.
3/2/10 Rule (Chimney Height)
Shorthand for the NFPA 211 chimney height requirement: the chimney must extend at least 3 feet above the highest point where it passes through the roof, AND at least 2 feet above any part of the building or obstruction within 10 horizontal feet. Both conditions must be satisfied; the more restrictive (taller) result governs. See the Chimney Height Guide.