Chimney Height Calculator
Determine the minimum required chimney height above the roofline using the 10-2-3 rule, NFPA 211, and IRC code standards. Enter your roof and chimney dimensions to get code-compliant clearance requirements instantly.
NFPA 211
IRC R1003
10-2-3 Rule
Roof Pitch Method
01
Building Parameters
Ridge Height (above grade)
Highest point of roof
22 ft
Eave Height (above grade)
Lowest edge of roof
9 ft
Chimney to Ridge (horiz.)
Measured along roof plane
8 ft
Current Chimney Height
Above roof deck/flashing
3 ft
Roof Pitch
02
Cross-Section Diagram
03
Required Minimum Height
Min. Required
—
above roof deck
Above Ridge
—
min 2 ft required
Clearance Status
—
current vs required
| Rule / Code | Requirement | Your Value | Status |
|---|---|---|---|
| 10-2-3 Rule ≥3 ft above roof at penetration; ≥2 ft above ridge within 10 ft |
— | — | — |
| NFPA 211 §13 Min. 3 ft above highest point of roof penetration |
3 ft min. | — | — |
| IRC R1003.9 Min. 3 ft above roof; ≥2 ft above ridge or obstruction within 10 ft |
3 ft min. | — | — |
| Pitch Correction Steep roofs (≥6/12) may require additional height |
— | — | — |
Adjust the sliders to evaluate your chimney’s code compliance.
04
Code Rules Explained
10-2-3
The Universal Rule
The chimney must extend at least 3 feet above the highest point where it passes through the roof. If any part of the roof (or another structure) is within 10 feet horizontally, the chimney must be at least 2 feet higher than that point. Covers the vast majority of residential installations.
NFPA 211
National Fire Protection
Standard for chimneys, fireplaces, vents, and solid fuel-burning appliances. Section 13 mandates the 3-foot / 2-foot-above-ridge requirements. This is the fire safety standard adopted by most jurisdictions and referenced by insurance requirements nationwide.
IRC §R1003
International Residential Code
Section R1003.9 of the IRC mirrors NFPA 211 requirements: chimney must be 3 ft above the roof at the point of penetration and at least 2 ft above any structure or roof within a 10-foot horizontal radius. Most US municipalities adopt the IRC as local building code.
⚠ Local Codes May Vary. Always verify requirements with your local building department or AHJ (Authority Having Jurisdiction). Some regions have adopted stricter standards. Gas appliance venting follows separate requirements under NFPA 54 / Z223.1. This calculator applies to solid-fuel (wood/pellet) chimneys.