How tall is a chimney, and how tall should it be?
Short answer. There is no single height: a chimney runs from its firebox or appliance to the top, and many fireplace and stove makers call for roughly 15 feet or more of total height for reliable draft, so two-story homes have noticeably taller chimneys. Above the roof, the code minimum is at least 3 feet above where it passes through and 2 feet higher than anything within 10 feet, and many chimneys are built taller for draft or looks.
Two different heights
- Total height affects draft. Taller flues pull harder, which is why a fireplace in a low addition can struggle while a two-story chimney draws well. Appliance instructions often state a minimum.
- Height above the roof is set by the 3-2-10 rule and by appearance. Exterior chimneys on Georgia homes are often built well above the minimum so they look proportional on a two-story front.
What a tall chimney means for the roof
- Crickets. The residential code requires a cricket on the uphill side of a chimney wider than 30 inches, measured parallel to the ridge, unless it meets the ridge. Wide chimneys on steep roofs collect a lot of water and needles behind them.
- Long flashing runs. A chimney rising through a steep roof has long sides of step flashing and long counterflashing, more seams to keep tight.
- Bracing. Factory-built chimneys that extend well above the roof need the manufacturer's bracing.
- Weather. The top courses, crown and cap take the most wind, rain and hail, so tall chimneys show wear and storm damage first.
- Access. Repairs on a tall chimney need roof brackets or scaffolding, which affects cost.
Can a chimney be too tall?
Very tall chimneys can draft too strongly for some stoves, which a sweep may correct with a damper, and a tall exterior chimney on a cold wall cools smoke faster, which builds creosote quicker. Structurally, tall masonry needs a sound footing and good mortar to resist leaning. See chimney leaks and crickets and roof flashing explained.