The basic steps for installing a dryer vent

Installing a dryer vent means running a duct from the back of your dryer to the outside of your home, then attaching an exterior vent cap so moist air can escape. The job takes two to four hours for most people and requires only basic tools: a drill, ductwork (usually 4-inch aluminum or flexible ducting), a vent cap, hose clamps, and a way to cut through your wall—either a hole saw if you're venting through a nearby exterior wall, or a longer duct run if the dryer is far from outside.

The most common mistake is venting into an attic, crawlspace, or garage instead of outside. Moisture trapped indoors rots framing, grows mold, and defeats the purpose of the dryer. A second mistake is using too many bends or too long a duct run without checking your dryer's manual—most dryers lose efficiency sharply after 25 feet of duct, and each 90-degree bend counts as extra length.

Key Takeaways

  • Dryer vents must run to the outside of your home, not into an attic or garage, because trapped moisture causes rot and mold.
  • Most residential dryers use 4-inch diameter ducting, but check your dryer's manual because some models differ.
  • The duct run should be as short and straight as possible—most manufacturers recommend no more than 25 feet total, counting each 90-degree bend as extra length.
  • An exterior vent cap with a damper (flapper) prevents outside air and pests from entering the duct when the dryer is off.
  • Flexible ducting is easier to install around obstacles, but rigid aluminum duct resists lint buildup better and lasts longer.

Choosing your vent route and ductwork type

Before you buy materials, decide whether you'll vent through an exterior wall near the dryer or run duct a longer distance. Venting through the nearest wall is always the best choice if possible—it's shorter, easier to install, and easier to clean. Measure the distance from the back of your dryer to the outside wall. If it's more than 8 to 10 feet, or if you have to make more than two 90-degree bends, the duct run becomes inefficient and lint accumulates faster.

Next, choose between flexible ducting and rigid aluminum duct. Flexible ducting (also called flex duct or accordion duct) is easier to route around obstacles and takes less time to install. Rigid aluminum duct is smoother inside, resists crushing, and sheds lint more easily—it's the better long-term choice if you can fit it. Many installers use rigid duct for the main run and a short flex section where the duct connects to the dryer, since dryers vibrate slightly during operation.

Check your dryer's manual for the correct duct diameter. Most household electric dryers use 4-inch ducting, but some compact or gas models use 3.25 inches. Using the wrong size creates air leaks and reduces airflow.

Cutting the hole and preparing the exterior opening

Mark the location on your exterior wall where the duct will exit. Choose a spot at least 12 inches away from any corner, window, or door, and at least 12 inches above ground level or snow line if you live in a cold climate. Avoid locations directly above a deck or patio where exhaust will blow onto people.

If you're venting through wood siding or vinyl, use a hole saw (4.25 inches for standard 4-inch duct) attached to a power drill. Drill from inside the house so you can see where the bit exits, then finish from outside. If you're venting through brick or stucco, you may need a masonry bit or a rotary hammer—this is the point where many homeowners call a contractor, since the work is slow and the tool rental adds cost.

Once the hole is cut, install the exterior vent cap from outside. Most caps have a flange that slides over the duct and a damper (flapper) that opens when air flows out and closes when the dryer is off. find the cap with the fasteners it comes with—usually screws or nails through the flange into the siding. Seal around the flange with exterior caulk to prevent water from running behind the siding.

Running the duct from the dryer to the wall

Disconnect the dryer's power before you work on it. Most dryers have a short duct or no duct at all when they arrive—you'll be adding the main run. Slide the duct onto the outlet at the back of the dryer and find it with a hose clamp (a metal band that tightens with a screw). Tighten the clamp firmly but not so hard that you crush the duct.

Route the duct toward the exterior wall, keeping bends as gentle as possible. If you must make a 90-degree turn, use an actual 90-degree elbow fitting rather than kinking the duct—kinks trap lint and reduce airflow. Support the duct every 4 to 6 feet with a strap or bracket so it doesn't sag and collect water or lint. Avoid running duct through walls, attics, or crawlspaces where you can't see it or clean it later.

When the duct reaches the wall, connect it to the exterior vent cap. If you're using rigid duct, use a connector fitting and hose clamps at each joint. If you're using flex duct, slide it over the cap's inlet and clamp it. Make sure the damper inside the cap moves freely—push it by hand to confirm it opens and closes without sticking.

Sealing joints and testing airflow

Every joint in the duct run should be clamped and sealed. Use foil tape (also called HVAC tape or duct tape—the real kind, not the gray cloth tape from a hardware store) to seal the seams where duct sections connect. Wrap the tape around the joint, overlapping by at least 2 inches. Do not use cloth duct tape; it degrades in the heat and humidity of a dryer vent.

Once everything is connected, reconnect the dryer's power and run it on high heat for 10 to 15 minutes. Go outside and feel the air coming from the vent cap—it should be warm and moist, and the damper should open fully. If the airflow is weak, check for kinks in the duct, too many bends, or a damper stuck closed. If the damper doesn't open, it may be clogged with lint or installed backward.

Common mistakes and how to avoid them

The most frequent error is venting into an attic or garage to avoid cutting through an exterior wall. This traps moisture indoors and causes mold, rot, and structural damage that costs thousands to repair. Venting outside is not optional—it's the only correct choice.

A second common mistake is using too much flexible ducting or making too many bends. Flexible duct has a corrugated interior that traps lint; rigid duct is smoother and sheds lint better. If your duct run is longer than 25 feet or has more than two 90-degree bends, lint will accumulate faster and you'll need to clean it more often.

Many people also forget to install a damper on the exterior vent cap, or they install one that doesn't move freely. Without a damper, cold outside air flows backward into the dryer when it's off, and pests can enter the duct. Test the damper by hand before you finish—it should move easily and seal completely when closed.

Finally, some installers use the wrong tape to seal joints. Cloth duct tape (the gray kind) breaks down in heat and humidity. Use foil tape instead, which is rated for high-temperature ducts and lasts the life of the vent.

When to call a professional

If your dryer is more than 30 feet from an exterior wall, or if you'd need more than three 90-degree bends to reach outside, a professional can advise whether the run is feasible or whether relocating the dryer makes sense. If you need to vent through brick, stucco, or stone, the work requires specialized tools and is usually faster and cleaner when done by someone with experience.

If your dryer is in a basement or interior room far from any exterior wall, a contractor can assess whether a longer duct run with booster fan is worth the cost, or whether moving the dryer to a more convenient location is the better choice. Some jurisdictions also require a permit for dryer vent installation—check with your local building department before you start.

Frequently Asked Questions

Can I vent my dryer into the attic or garage instead of outside?

No. Venting indoors traps moisture that rots wood framing, grows mold, and damages insulation. The moisture also makes your home harder to heat or cool. Venting must go to the outside of your home.

What size duct do I need?

Most household electric dryers use 4-inch ducting. Some compact or gas models use 3.25 inches. Check your dryer's manual or the outlet on the back of the unit to confirm the correct size before you buy materials.

How often should I clean the dryer vent?

Clean the vent at least once a year, or more often if you dry a lot of laundry or notice the dryer taking longer to dry clothes. Lint buildup reduces airflow, makes the dryer work harder, and is a fire hazard. A professional vent cleaning takes 30 to 60 minutes.

Can I use regular duct tape to seal the duct joints?

No. Cloth duct tape breaks down in the heat and humidity of a dryer vent. Use foil tape (HVAC tape) instead, which is rated for high temperatures and lasts much longer.

What if the dryer vent damper is stuck closed?

A stuck damper usually means lint has built up inside the vent cap or duct. Disconnect the duct at the cap, look inside with a flashlight, and remove any lint by hand or with a brush. If the damper still won't move, the cap may need to be replaced.