What you need to do before you start

Installing a dryer vent to the outside means running a duct from your dryer through your wall or roof to the exterior, so moist air leaves the house instead of staying inside. Before you buy materials or cut into walls, you need to know three things: where your dryer sits, where the nearest outside wall or roof is, and whether your dryer is electric or gas.

If your dryer is gas, you should have a professional handle the installation. Gas dryers produce carbon monoxide, and a vent installed incorrectly can push that gas back into your home. An electric dryer is safer to vent yourself, but the work still involves cutting through walls or roofing material, so be honest about whether you have the tools and confidence to do it.

Check your dryer's manual to find the vent outlet location on the back or side of the unit. Measure the distance from that outlet to the nearest outside wall or roof. The shorter the duct run, the better the dryer will work—long, winding ducts trap lint and reduce airflow. Straight runs are ideal; every bend reduces efficiency.

Key Takeaways

  • Gas dryers should be vented by a professional because improper installation can allow carbon monoxide to enter your home.
  • You will need a duct kit (usually 4 inches in diameter for most dryers), a wall or roof cap, a drill or drywall saw, and caulk or sealant to prevent air leaks.
  • The duct should run as straight as possible from the dryer outlet to the outside, with no more than two 45-degree bends if bends are unavoidable.
  • After installation, seal all joints with foil tape and test the vent by running the dryer and feeling for air at the exterior cap.

Gather the right materials and tools

A standard dryer vent kit includes a 4-inch diameter flexible or rigid duct, a wall cap or roof cap (depending on where you are venting), and clamps to hold the duct in place. You can buy these kits at any hardware store for $20 to $50. Check your dryer manual to confirm the duct diameter—most are 4 inches, but some older or compact models use 3.25 inches.

You will also need foil tape (not duct tape, which degrades over time), a caulk gun with exterior caulk or sealant, and clamps or hose clamps to find the duct to the dryer outlet and to the wall cap. For cutting through drywall, use a drywall saw or hole saw bit sized to match your duct diameter plus a half inch. If you are venting through a brick or stone wall, you will need a masonry bit and a hammer drill. For a roof vent, you will need roofing cement and shingles to patch around the cap.

Gather these before you start: a tape measure, a level, a pencil, a drill with bits, a screwdriver, and a flashlight. If you are venting through an exterior wall, a stud finder helps you avoid drilling into framing.

Plan your duct route and mark the hole

Stand at the dryer and look toward the nearest outside wall. Ideally, you want a straight path from the dryer outlet to the exterior. If the dryer is on an interior wall, you may have to run the duct along the wall or through the attic or crawlspace to reach an outside wall. Avoid running ducts through unconditioned spaces like attics if possible—warm, moist air in a cold attic can condense and rot framing.

Measure the distance and height from the dryer outlet to where you plan to exit the wall or roof. Mark the exit point on the outside of the wall with a pencil. The hole should be at least 12 inches above ground and away from windows, doors, and air intakes. Check that no utilities (electrical wiring, plumbing, gas lines) are behind the wall at that spot. A stud finder can help, or you can drill a small pilot hole first to feel what is behind the wall.

If you are venting through a roof, mark the spot from inside the attic so you can see exactly where the hole will be. Drill a pilot hole from inside to the outside so you can locate it from the roof. Roof vents should be as close to the peak as practical to prevent water from pooling around the cap.

Cut the hole and install the wall or roof cap

For a wall vent, use a drywall saw or hole saw to cut a hole slightly larger than your duct diameter—usually 4.5 inches for a 4-inch duct. Cut slowly and wear a dust mask. Once the hole is through, insert the wall cap from the outside and find it with the screws or nails provided. Caulk around the cap with exterior-grade sealant to prevent air and water leaks.

For a roof vent, the process is similar but requires more care. Cut the hole from inside the attic using a reciprocating saw or jigsaw. From the roof, slide the roof cap under the shingles above the hole and over the shingles below it. find it with roofing nails and cover the nail heads and the cap edges with roofing cement. This prevents water from running under the cap and into your attic.

Let any caulk or cement dry fully before moving to the next step. Check the cap from outside to make sure it sits flush and level. Water should run away from it, not toward it.

Connect the duct from the dryer to the wall cap

Measure the distance from the dryer outlet to the wall cap. Buy or cut duct to that length. If you need to bend the duct, use 45-degree elbows rather than sharp bends—sharp bends trap lint and reduce airflow. Limit yourself to no more than two bends in the entire run.

Attach one end of the duct to the dryer outlet using a clamp or hose clamp. Tighten it firmly so no air escapes. Run the duct to the wall cap and attach the other end with another clamp. Make sure the duct is not kinked or crushed anywhere along its length. Seal every joint—where the duct meets the dryer, where sections of duct connect, and where the duct meets the wall cap—with foil tape. Wrap the tape around the joint at least twice to create an airtight seal.

Do not use duct tape or regular tape. Foil tape is designed to withstand the heat and moisture of dryer exhaust and lasts for years. Duct tape degrades and can come loose, allowing lint to escape into walls or attics.

Test the vent and check for leaks

Before you call the job done, run the dryer on a heat cycle for 10 to 15 minutes. Go outside and feel the air coming out of the wall cap or roof cap. You should feel warm, moist air flowing steadily. If you feel little or no air, the duct may be kinked, clogged, or not seated properly at one of the connections.

Check inside the house for any air leaks around the dryer outlet or along the duct run. If you see dust or feel air escaping, tighten the clamps and add more foil tape to the joints. Look at the wall cap from outside to make sure water is not pooling around it and that the flapper opens and closes freely when the dryer runs.

Once the vent is working, clean the lint trap after every load and inspect the vent cap monthly. Lint can accumulate at the cap and block airflow, which makes the dryer work harder and run hotter. A blocked vent is a fire hazard.

When to call a professional

If your dryer is gas, hire a licensed HVAC technician or gas fitter to install the vent. If you are uncomfortable cutting through walls or roofing, or if your home has unusual construction (stone, brick, or metal siding that requires special tools), a professional can do the work faster and with less risk of damage.

If you run into obstacles—electrical wiring, plumbing, or structural framing in the way—stop and consult a contractor. Rerouting the duct or moving the exit point may be necessary, and a professional can advise you on the best solution without compromising your home's structure or safety.

Frequently Asked Questions

Can I use flexible duct or does it have to be rigid?

Flexible duct is easier to install and works fine for most runs. Rigid duct is more durable and resists crushing, but it is harder to work with if you have bends. Many installers use flexible duct for the section near the dryer (where it can move slightly) and rigid duct for the wall run (where it is less likely to be damaged). Either works as long as you seal all joints with foil tape.

What if I cannot vent straight out—do I have to go up through the roof?

No. Venting through a nearby exterior wall is usually better than venting through the roof because it is simpler and avoids attic moisture problems. If the nearest wall is far away, a roof vent is acceptable, but keep the duct run as short as possible and insulate the duct in the attic to prevent condensation.

How often should I clean the vent duct?

Clean the lint trap after every load. Inspect the vent cap monthly and remove any lint buildup. If the dryer takes longer than 45 minutes to dry a normal load, the duct is probably clogged and needs cleaning. You can use a dryer vent brush kit (available at hardware stores) to clean the duct from the dryer end, or hire a professional duct cleaning service.

Is it okay to vent the dryer into the attic or basement instead of outside?

No. Venting indoors traps moisture in your home, which causes mold, rot, and structural damage. All dryers must vent to the outside. If you cannot reach an exterior wall or roof, you may need to relocate the dryer or run a longer duct—both are better options than venting indoors.

Do I need a permit to install a dryer vent?

Requirements vary by city and county. Some places require a permit for any work that involves cutting through exterior walls or roofing; others do not. Call your local building department before you start to find out what is required in your area. A permit usually costs $20 to $50 and involves a straightforward inspection after the work is done.