Chimney height from the 3-2-10 rule, pipe sections, flashing, bracing and hearth pad cost.
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
⚠ The chimney needs to run 6.0 ft above the roof to satisfy the 3-2-10 rule at this pitch and ridge distance — anything over 5 ft above the roofline needs additional bracing beyond the base roof bracket, which is included above. Follow the pipe manufacturer's brace spacing exactly; an unsupported run flexes in wind and stresses the flashing seal.
⚠ This calculator assumes a listed double-wall connector pipe, which allows roughly 6 in of clearance to combustibles. Single-wall connector pipe needs about 18 in — nearly three times the clearance — so if your stove's manual specifies single-wall, re-check every clearance in the room before you buy.
⚠ Route the chimney between joists and rafters rather than cutting either — a 6 or 8 in flue with its required clearance almost always fits in a standard 16 or 24 in bay. If an obstruction forces a cut, that framing member needs to be doubled and headed off before you open the hole.
⚠ Local code and your stove's listing govern over these generic minimums — many jurisdictions require a permit and a final inspection for a new solid-fuel chimney, and the manufacturer's installation manual can call for more clearance or a taller run than the 3-2-10 rule alone.
| Plumbing & Heating | $781–$1,057 |
| Tile & Stone | $289–$391 |
| Roofing | $64–$86 |
| Finishing & Sealant | $15–$21 |
| Fasteners & Hardware | $7–$9 |
| Total | $1,156–$1,564 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
These are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
About this calculator
Give the Wood Stove Chimney Calculator your roof pitch and how far the chimney sits from the ridge, and it applies the 3-2-10 rule to find the shortest legal height above the roof — then works backward from there to the whole parts list: double-wall connector pipe from the stove to the ceiling or wall, a support box or thimble, Class-A insulated chimney sections sized to your attic or exterior run, flashing matched to your pitch, a storm collar, spark-arrestor cap and roof bracing.
Pick an interior route through the ceiling and attic or an exterior route up an outside wall, and the parts list changes to match — the exterior run adds a horizontal-to-vertical tee and wall straps instead of a ceiling firestop box. It also sizes a hearth pad from your stove's footprint and clearance-to-combustibles rating. This is a planning estimate; your stove's manual and local code always govern over these general minimums.
Step by step
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
Decide between an interior route through the ceiling and attic or an exterior route up an outside wall, then use your roof pitch and distance to the ridge to work out the minimum chimney height under the 3-2-10 rule before you cut anything.
Mark the ceiling and roof penetration so it falls between joists and rafters rather than through one — a 6 or 8 inch flue with its clearance almost always fits a standard bay without any structural cutting.
Install the firestop component that carries the transition from connector pipe to Class-A — a ceiling support box for the interior route, or a wall thimble and tee for the exterior route — square and level before anything stacks on top of it.
Assemble double-wall connector pipe from the stove's flue collar up to the support box or thimble, crimped end down so any condensation runs back toward the stove instead of dripping through a joint.
Build up Class-A insulated sections through the attic or up the exterior wall, twist-locking each joint and securing wall straps on an exterior run roughly every 4 feet.
Cut the roof opening to the flashing manufacturer's template, set the adjustable flashing matched to your pitch, and fit the storm collar above it, sealing every lap with high-temperature sealant, not standard caulk.
Continue the Class-A run to the height the 3-2-10 rule requires for your pitch and ridge distance, adding the roof support bracket at the deck and any additional bracing the manufacturer calls for above 5 feet of exposed run.
Install the spark-arrestor cap, then size and set the hearth pad so it extends past the stove's footprint by the full clearance-to-combustibles distance on every side before the stove goes into service.
Equip the job
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Interior & Finishing
Answers
It's the height rule most codes use for a chimney's termination point: the top has to sit at least 3 feet above the roof surface where it passes through, and at least 2 feet above any part of the roof — including the ridge, a dormer or an adjacent wall — within a 10-foot horizontal radius. If the ridge or another obstruction is close enough to matter, the 2-foot clearance usually forces the chimney taller than the flat 3-foot minimum, which is exactly what this calculator solves for using your pitch and ridge distance.
A straight interior run through an attic with a modest above-roof height typically lands between $1,200 and $2,000 in materials — Class-A insulated pipe is the single biggest line item, followed by the hearth pad and the ceiling support box or wall thimble. An exterior wall-mounted chimney usually costs more because it needs more Class-A footage and wall strap brackets to reach the same height above the roof. Professional installation, including any framing changes, commonly runs several times the materials total.
Class-A insulated pipe is required anywhere the chimney passes through a ceiling, attic, wall cavity or the roof itself, and above the roofline — anywhere it's near combustible framing or exposed outdoors. Only the short connector segment between the stove's flue collar and the ceiling support box or wall thimble uses connector (stove) pipe, which is a lighter double- or single-wall product rated for a room, not a concealed space. Mixing them up — running connector pipe through a wall or attic — is a serious fire-code violation.
Floor protection has to extend past the stove's footprint on every side by a distance set by the stove's clearance-to-combustibles rating — commonly 8 to 18 inches depending on whether it's a modern EPA-certified stove with a tight UL listing or an older, unlisted one. This calculator adds that clearance around your stove's footprint and matches the result to the nearest stock hearth pad kit size, or flags a custom cut-to-size pad if your stove and clearance combination runs larger than the biggest stock kit.
An interior chimney running up through the attic stays warmer along its whole length, which keeps flue gas above its condensation point and produces less creosote — generally the better-performing option where the framing allows it. An exterior chimney bolted up an outside wall is often easier to retrofit into a finished house since it avoids cutting the ceiling and roof deck together, but it runs cold on every side and must use pipe rated for outdoor, cold-climate exposure, or creosote builds up fast enough to become a chimney-fire risk.
At least once a year for a stove used as a primary heat source, and always before the first fire of a new heating season — creosote is a normal byproduct of burning wood and it accumulates on the flue walls every time the stove runs, regardless of how well the chimney is sized. A taller or cooler-running chimney, green or unseasoned firewood, and long, low-and-slow burns all speed up the buildup, so check more often in those cases rather than waiting for the annual mark.