Can a Dryer Vent End Under a Deck?

How a Hood Ends Up Under a Deck

One way it happens: the duct went out the wall behind the laundry, and years later a deck was built against that wall, right over the hood. Sometimes the deck is high and open and the hood barely notices. Sometimes the deck sits a foot off the ground with skirting around it, and the hood now blows into a dark box.

The code question and the practical question are the same: does the air have somewhere to go, and can anyone reach the hood to clean it?

What the Rules Say

No section of the 2023 Florida Building Code, Residential, names a deck. Section M1502.3 asks that the duct terminate on the outside of the building with a backdraft damper and no screen, and section M1501.1 rules out an attic, soffit, ridge vent or crawl space. Section M1502.1 makes the dryer maker's installation instructions part of the rule.

Those instructions are where a deck runs into trouble. GE's say to keep a minimum of 12 inches between the vent hood and the ground or any other obstruction, to avoid restricting the outlet, and not to obstruct the exhausted air. A Whirlpool compact dryer sheet says the hood must be at least 12 inches from the ground or any object in the path of the exhaust. Deck joists, a beam, lattice skirting or the ground under a low deck can all sit inside that 12 inches.

There is a second line in GE's instructions worth reading against an enclosed deck: a dryer must not be exhausted into any concealed space of a building where lint can accumulate. A fully skirted space under a deck attached to the house is not named as such, but it behaves like one.

• 12 inches clear below the hood, to the ground.
• 12 inches clear in front of the hood, to joists, beams or skirting.
• A flap that opens fully and closes again.
• A way to reach the hood for cleaning without removing deck boards.
• Open air around it, not a skirted, enclosed space.

Why Low Decks Cause Trouble

A dryer pushes out warm, damp air with lint in it. Under an open, high deck that air drifts away. Under a low, skirted deck it has nowhere to go: the damp air hangs against the joists and the underside of the boards, and lint drops onto the ground below the hood and stays there, building up around the flap.

Cleaning is the other problem. A hood you cannot reach does not get its flap cleared or its lint picked out, and a blocked flap backs lint up the whole duct. If you have to lift deck boards or crawl through a gap to see the hood, it is in the wrong place.

Where to Move the Hood

The first choice is a different wall: the nearest outside wall clear of the deck, if the route there fits within the dryer's length chart. Next is a higher spot on the same wall, above the deck surface, where the hood also keeps 3 feet from windows and doors under section M1502.3. A third choice is to carry the duct beneath the deck to a hood past its edge, in smooth metal, supported at intervals no greater than 12 feet; every foot and elbow of that extension counts against the dryer's limit, so it works only on short runs.

Each option closes the old opening under the deck, so the hood cannot keep blowing into the space behind the skirting.

Looking at the Hood Under Your Deck

Run the dryer and look at the hood from the edge of the deck with a light. Is the flap lifting? Is there lint on the ground below it or on the joists in front of it? Measure from the hood to the ground and to the nearest joist, beam or skirting board. If anything is within 12 inches, or you cannot see the hood without crawling under, the hood needs to move. Do not crawl under a low deck with the dryer running or into a space you cannot easily back out of.

Getting It Moved

Moving a hood out from under a deck is dryer vent installation work: a new opening, a duct to it and the old hole closed. Our guide on dryer vent distance from windows and the AC unit covers the rules the new spot has to meet.

Our experienced crew works under decks and eaves for a locally owned, family-owned company that is Proudly American. Ask for a free inspection: the hood, the possible routes and the dryer's chart get measured, and the written estimate follows. If your deck is high and open enough to leave the hood alone, our Proudly American technicians will say so.