How to clean a dryer vent from outside or on the roof

Updated September 23, 2026 · Every figure checked twice against its source · How we verify

To clean a dryer vent from outside, find the hood on the wall or roof, pull out lint and any nesting material, check the flap swings freely, then feed a rotating brush into the duct toward the house and vacuum out what it loosens. A roof vent is the same job with a fall risk, which is why HomeGuide prices roof vent cleaning at $150 to $250 against $80 to $185 for a standard vent.

Where is my dryer vent outside?

Start at the wall behind the dryer and look for the matching spot on the outside wall: a hood with a flap or louvers. If there is none, the duct runs somewhere else, through the basement ceiling, up through the attic to the roof, or out a side wall. Follow the duct from the back of the dryer to find it.

The International Residential Code says the duct must end outside the building (section M1502.3). Where the dryer maker does not specify a location, it must end at least 3 feet from any opening into the building, including ventilated soffits. The USFA warns that faulty installations sometimes vent into the attic, crawl space, chimney or wall cavity. If the duct ends inside, it needs a repair, not a cleaning: see dryer vent repair.

How to clean dryer vent from outside

1. Turn the dryer off. For a full cleaning, unplug it too.
2. Clear the hood. Pull out lint and any nest from the opening and behind the flap or louvers. Wear gloves for nesting material.
3. Check the flap. It should swing freely. The NFPA says the outdoor flap should open when the dryer runs and must not be covered by snow.
4. Brush inward. Feed a rotating brush into the duct toward the house, adding rod sections as it goes, and pull it back often to empty the lint.
5. Vacuum the loosened lint from the outside end, then from inside at the dryer end if you can reach it.
6. Run the dryer and watch the hood. A strong, steady flow of warm air and an open flap mean the run is clear.

Cleaning only from outside leaves out the hose behind the dryer. Once a year, do the full job from inside as well; our guide on how to clean a dryer vent covers it.

How to clean exterior dryer vent hoods: what not to add

The code allows no screen at the duct termination: "Screens shall not be installed at the duct termination" (IRC M1502.3). The USFA agrees that wall dampers need a covering against rain, snow and dirt, but says not to use wire screen or cloth, which collect lint and clog the vent. The code also requires a backdraft damper at the termination and an opening of at least 12.5 square inches (M1502.3 and M1502.3.1).

That matters for products sold as an outside dryer vent lint catcher or outside dryer lint trap. A device that puts mesh across the exhaust at the termination conflicts with that rule. If you have one, ask your local building department before relying on it.

How to clean dryer vent on roof

A roof vent runs up through the attic and ends in a roof cap. Cleaning it means clearing the cap and brushing the duct downward, then vacuuming from the dryer end. Fixr says roof vents are more exposed to the elements and clog more than wall vents, and HomeGuide says these vertical vents are more prone to mold from roof leaks.

Roof work carries a fall risk. Unless you are comfortable and equipped on a roof, this is the one to hire out; here is what a professional dryer vent cleaning service should include.

How to clean dryer vent without going on roof

Work from the bottom. Disconnect the duct at the dryer and feed the brush up the run toward the roof cap, pulling it back often so lint falls toward you, then vacuum at the bottom. This cleans the duct but not the cap, where nests and lint collect. If the flap or cap is blocked, it still needs someone on the roof.

Lint coming out of outside dryer vent

Some lint in the exhaust is expected: the USFA says lint is carried through the vent system along with the moist air. Lint collecting on the hood is a cue to clean it; Massachusetts' Department of Fire Services says to clean outside vents twice a year. A sudden increase can mean the lint screen is torn or loose, and the USFA says not to run a dryer with a lint filter that is loose, damaged or clogged.

Sources

1. International Code Council, 2021 International Residential Code, section M1502: codes.iccsafe.org
2. U.S. Fire Administration, "Clothes Dryer Fires in Residential Buildings (2008 to 2010)", August 2012: usfa.fema.gov
3. NFPA, "Clothes dryer safety" tip sheet: nfpa.org
4. Massachusetts Department of Fire Services, "Dryer Fire Safety": mass.gov
5. HomeGuide, "How much does dryer vent cleaning cost?", page dated April 29, 2024: homeguide.com
6. Fixr, "Dryer vent cleaning cost", updated January 31, 2025: fixr.com

All sources read September 23, 2026.