How to Replace Dryer Duct: Materials, Steps, and Safety
Learning how to replace dryer duct is a practical home improvement project that directly improves safety. Dryer duct replacement is most often needed when the existing duct is made from unsafe flexible plastic or foil accordion material — materials that are highly prone to lint accumulation, are combustible, and are no longer permitted in new residential construction under most building codes. Replacing unsafe duct with rigid metal is the single most significant improvement you can make to a dryer vent system. This guide covers what materials to buy, how to remove the old duct, and how to install the new duct correctly and safely.
When Dryer Duct Replacement Is Needed
Not every dryer vent problem requires duct replacement. But these situations do:
Plastic or foil accordion duct. The corrugated, flexible "slinky" style duct — available in white plastic and shiny foil — has been used for decades as a low-cost, easy-to-install option. It is also a documented fire hazard. The ridged interior traps lint at every fold. When heated, plastic can warp, melt, or ignite. Foil will not burn but can disintegrate in a fire. Many fire safety organizations explicitly recommend replacement with metal duct.
Crushed or kinked duct. A flexible connector that has been squeezed by the dryer sliding against the wall, or a rigid duct section that has been stepped on or damaged during construction, restricts airflow and cannot be restored by cleaning.
Disconnected sections. Duct that has separated at a joint leaks moist, lint-laden air into wall cavities, contributing to mold growth and structural damage.
Non-compliant configuration. Duct runs exceeding 35 feet, or runs with too many bends for their length, may need to be rerouted rather than cleaned.
Choosing the Right Duct Material
The material choice determines long-term safety and maintenance requirements:
Rigid aluminum duct (4-inch diameter) is the top choice for the in-wall or in-ceiling duct run. The smooth interior surface minimizes lint accumulation and allows lint to flow through more easily. Sold in 2-foot rigid sections at hardware stores.
Rigid galvanized steel duct is equally safe and slightly more durable. Choose either aluminum or galvanized, but do not mix parts from both in a single run — they use different joining methods.
Semi-rigid aluminum flex duct is appropriate for the short connector section between the dryer exhaust port and the wall — typically 12 to 24 inches. It allows for slight positional adjustment when moving the dryer without disconnecting the full duct. Do not use it for long in-wall runs.
What to avoid: Plastic accordion duct (white corrugated), foil accordion duct (shiny corrugated), and any flexible duct that is not UL-listed semi-rigid aluminum.
| Duct Material | Code Compliant? | Fire Safety | Lint Accumulation | Approx. Cost (per ft) |
|---|---|---|---|---|
| Rigid aluminum | Yes | Best | Lowest | $2–$4/ft |
| Rigid galvanized steel | Yes | Best | Lowest | $2–$5/ft |
| Semi-rigid aluminum | Yes (short runs) | Good | Low | $3–$5/ft |
| Foil accordion (corrugated) | No (new installs) | Poor | High | $1–$2/ft |
| Plastic accordion (white) | No | Worst | Very high | $0.50–$1.50/ft |
How to Replace Dryer Duct: Step by Step
- 1
Measure the existing duct route and plan the new one
Measure the distance from the dryer exhaust port to the exterior vent cap. Count the number of bends. The total duct length must not exceed 35 feet, minus 5 feet per 90-degree elbow and 2.5 feet per 45-degree elbow. Buy enough rigid duct sections and fittings to complete the run.
- 2
Disconnect and remove the old duct
Unplug the dryer, close the gas valve if applicable, and pull the dryer away from the wall. Disconnect the flexible connector from the dryer exhaust port. Remove the entire old duct run — pull it out through the wall opening or from the exterior vent cap end.
- 3
Clean the duct opening and exhaust port
Vacuum lint from the dryer exhaust port and from the interior of the wall duct opening. If the old duct left adhesive residue or lint deposits on the wall opening, clean these away before installing new duct.
- 4
Install the exterior vent cap (if replacing)
From outside, install the new exterior vent cap. Cut the through-wall duct pipe to the correct length (same as the original), slide it through the wall, attach the cap to the siding using the provided screws, and seal around the perimeter with exterior caulk.
- 5
Assemble the interior rigid duct run
Starting at the wall, connect rigid duct sections toward the dryer, using elbows as needed for turns. Join sections by overlapping the crimped (narrow) end of one piece into the next. Do not use screws inside the duct — they snag lint. Seal all joints with metal foil tape.
- 6
Install the flexible connector
Cut a length of semi-rigid aluminum flex duct to bridge from the last rigid duct section to the dryer exhaust port. Keep it as short as practical. Secure with hose clamps at both ends and ensure there are no sharp bends.
- 7
Slide dryer back and test
Push the dryer back into position without crushing the flexible connector. Restore power and gas. Run a full drying cycle and check the exterior vent cap — the flap should open fully and you should feel strong, warm airflow.
Building Code Requirements
Dryer duct installation is governed by the International Residential Code (IRC M1502) and local codes. Key requirements:
- •Maximum duct length: 35 feet (minus 5 feet per 90-degree elbow, 2.5 feet per 45-degree elbow)
- •Minimum duct diameter: 4 inches
- •Duct must terminate to the exterior — not to a crawlspace, attic, or wall cavity
- •Exterior cap must be equipped with a backdraft damper
- •No screens at the exterior termination (lint clogs them)
- •All joints must be sealed with metal foil tape — not standard duct tape
- •Rigid metal or UL-listed semi-rigid aluminum only
Not sure whether to DIY or hire a professional? LintSnap can assess your current duct, recommend replacement when needed, and handle cleaning for a flat $149.
Get a Professional Assessment →Cost of Dryer Duct Replacement
The cost depends on the scope of the project:
Flexible connector only (semi-rigid, 12–24 inches): $15 to $40 in materials, 30 minutes of work.
Exposed accessible duct run (not in walls): $30 to $80 in materials, 1 to 2 hours of work.
Full replacement including in-wall duct: $50 to $120 in materials if you DIY the accessible sections. Professional replacement typically costs $150 to $500 depending on how much of the duct is inside walls.
New installation through an exterior wall: $200 to $800 for professional installation.
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