The basic route: drill, insert duct, seal it

Running a dryer vent through a wall means drilling a hole from inside your laundry room to the outside, then feeding a metal duct through it and sealing the gap. The hole is typically 4 inches in diameter for a standard dryer. You'll need a drill with a spade bit or hole saw, a length of rigid or semi-rigid metal duct, a wall cap (the fitting that covers the hole on the outside), caulk, and about an hour of work.

The process itself is straightforward: locate where you want the vent to exit, drill through the wall from inside, push the duct through, attach the wall cap on the outside, and seal around it with caulk. The trickiest part is usually finding a spot that doesn't hit studs, pipes, or electrical wiring inside the wall. A stud finder helps, but if you're uncertain about what's inside your wall, a drywall saw and a flashlight let you peek before committing to the full hole.

Key Takeaways

  • A standard dryer vent hole is 4 inches in diameter and requires a spade bit or hole saw, metal duct, a wall cap, and exterior caulk.
  • Locate your hole away from studs and electrical outlets by using a stud finder and checking both sides of the wall before drilling.
  • Rigid metal duct lasts longer than flexible foil duct and resists lint buildup better, though it is harder to route around obstacles.
  • Seal the gap between the duct and wall opening with caulk on the outside; do not rely on caulk alone to hold the duct in place.
  • The duct should slope slightly downward as it runs from the dryer to the wall opening to prevent moisture from pooling inside.

Finding the right spot on your wall

Before you drill, walk outside and look at where you want the vent to exit. Pick a spot that is visible and accessible for cleaning—you'll need to clear lint from the outside cap periodically. Avoid spots directly above a deck, patio, or window, since lint and moisture will blow onto those areas. A side wall of the house is usually better than a gable end, because wind pressure is less likely to push air back into the duct.

Once you've chosen the outside location, go back inside and mark that spot on the wall. Use a stud finder to check for wooden studs on both sides of the wall. If the stud finder shows a stud where you want to drill, move your mark 16 inches to the left or right—studs are typically spaced 16 inches apart. If you're still uncertain, use a drywall saw to cut a small exploratory hole, shine a flashlight through it, and look for pipes or wiring. Patch the small hole with spackle afterward.

Drilling the hole and inserting the duct

Use a 4-inch spade bit or hole saw attached to a drill. A hole saw is cleaner and faster, but a spade bit works if that's what you have. Drill from inside the house, pushing straight through the wall. Go slowly and let the bit do the work—forcing it will bind the drill. Once the bit breaks through the outside, stop and remove the drill.

From outside, you may need to enlarge the hole slightly or clean up the edges with a utility knife. Push the metal duct through the hole from inside. The duct should fit snugly but not so tight that you can't move it. Attach the wall cap to the outside end of the duct—most caps have a flange that overlaps the wall, and you find it with the small screws or rivets that come with the cap. Make sure the cap's damper (the flap that opens when air flows) moves freely and isn't blocked by lint or debris.

Connecting the duct to your dryer

Inside, the duct that runs through the wall needs to connect to the outlet on the back of your dryer. Measure the distance from the dryer to the wall opening and cut or bend your duct to fit. If you're using rigid duct, you may need an elbow fitting to change direction. If you're using flexible foil duct, you can bend it gently, but avoid sharp kinks that trap lint.

Slide the duct onto the dryer outlet and find it with a hose clamp or duct tape. Tighten the clamp so the duct doesn't slip off when the dryer runs. The duct should slope slightly downward as it runs toward the wall—a drop of about 1/4 inch per foot is ideal. This slope prevents moisture from collecting inside the duct and dripping back toward the dryer.

Sealing and insulating the opening

Once the duct is in place and the wall cap is attached, seal the gap between the duct and the wall opening with exterior caulk. Use a caulk gun and explore a continuous bead around the entire opening on the outside of the house. Smooth it with a wet finger or caulk tool so it sits flush against both the duct and the wall. This prevents air leaks and keeps insects and rain out of the gap.

Do not rely on caulk to hold the duct in place—it is a seal, not a fastener. The duct should be supported by the wall cap and the connection at the dryer. If the duct sags between the dryer and the wall, add a duct support bracket or hang it with a wire loop from a ceiling joist to keep it level.

Rigid versus flexible duct: which to choose

Rigid metal duct is the better choice for a through-wall installation. It resists crushing, doesn't trap lint as easily as flexible duct, and lasts 15 to 20 years or longer. The downside is that it's harder to route around obstacles and requires elbows and connectors if you need to change direction.

Flexible foil duct is easier to install if your path is not straight, and it costs less. However, it can kink, which blocks airflow and traps lint. It also degrades faster—typically 5 to 10 years—and is more prone to tearing. If you use flexible duct, keep the run as short and straight as possible, and avoid bending it sharply.

Common mistakes to avoid

The most common error is running the duct downward as it leaves the dryer, which causes moisture to pool inside. The duct should always slope downward toward the wall opening, not away from it. Another mistake is using too many elbows or bends, which increases resistance and makes the dryer work harder. Each 90-degree elbow adds the equivalent of about 5 feet of straight duct to the system's resistance, so minimize turns.

Don't drill into a stud or electrical wire—this is why the stud finder matters. Don't forget to install the wall cap on the outside; without it, rain and insects will enter the duct. And don't seal the inside connection between the duct and dryer with caulk; use a hose clamp instead, because caulk will crack and fail when the duct vibrates during the dryer cycle.

Frequently Asked Questions

Can I run the dryer vent through an interior wall instead of an exterior wall?

No. Interior walls lead nowhere, and the moist air will condense inside the wall cavity, causing mold and rot. The vent must exit to the outside of the house. If your laundry room is in the center of the house, you may need to run the duct a longer distance, but it must reach an exterior wall or roof.

What size hole do I need for a standard electric dryer?

A standard electric dryer uses a 4-inch duct, so you need a 4-inch hole. Gas dryers also use 4-inch ducts. Some older or compact dryers may use 3-inch ducts, so check your dryer's manual or the outlet on the back of the unit before you drill.

Do I need to insulate the duct after it goes through the wall?

Insulation is not required, but it can help in cold climates. If warm, moist air travels through an uninsulated duct in a cold wall cavity, condensation may form inside the duct. Wrapping the duct with foam pipe insulation reduces this risk. It also slightly improves dryer efficiency by keeping the air warm as it travels to the outside.

How often should I clean the outside vent cap?

Check the cap every month and clear any lint buildup around the damper. A clogged cap forces the dryer to work harder and can cause heat to back up into the laundry room. If you notice the dryer taking longer to dry clothes, a blocked vent cap is often the culprit.

Can I use PVC pipe instead of metal duct for the dryer vent?

No. PVC is not rated for the heat and moisture that dryer vents produce, and it can warp or release fumes. Metal duct is required by building codes and manufacturer specifications. Stick with rigid or flexible metal duct only.