A dryer vent that is clogged in the wall shows itself the same way as any other clog: long drying times, a hot dryer and a weak flap outside. To find where the blockage is, test the system one section at a time, starting with the hose behind the dryer, then the hood outside, and finally the duct inside the wall. Wall sections clog most at elbows, at crushed or flexible duct and at joints held with screws. You can safely clear the hose and the hood yourself and gently brush a rigid run, but a crushed or disconnected duct inside the wall needs to be opened and repaired.
The three places a vent gets blocked
Every dryer vent has three parts, and each clogs for different reasons.
| Section | Where it is | Typical cause of a blockage |
|---|---|---|
| Transition hose | Behind the dryer, from the dryer outlet to the wall | Crushed when the dryer is pushed back, lint caught in the ridges |
| Wall or attic run | Inside the wall cavity, ceiling or attic | Lint at elbows, crushed duct, screws in joints, sags, disconnection |
| Termination | Wall hood or roof cap outside | Lint packed in the louvers, stuck damper, nest, screen |
How to tell where the blockage is
Turn the dryer off and unplug it or switch off its breaker before you pull it out. Then work through these checks.
1. Check the dryer and hose together. Disconnect the hose at the wall end, hold it pointed into a bag or bucket, and run the dryer on a no heat or air only setting for a minute. You should feel a strong, steady stream of air. If it is weak, the problem is the lint filter, the filter housing, the hose or the dryer itself.
2. Look at the hose. Check for kinks, flattened sections and tears. Shake it out or replace it with a short, listed hose. The code limits the transition to 8 feet and does not allow it to be hidden in the wall.
3. Check the hood. Reconnect everything and run the dryer. Outside, the flap should open fully and you should feel warm air. Look for lint in the louvers, a nest, a screen or a damper stuck half closed. Clear what you can reach safely from the ground.
4. Decide. If the dryer blows well with the hose disconnected, and the hood is clear but the flap still barely moves, the restriction is in the wall or attic section. That is the part to clean or open.
Why the wall section clogs
The duct inside the wall is out of sight, and it is where most installation shortcuts hide.
The elbow at the bottom. In many Florida homes the duct enters the wall low, turns 90 degrees and runs up into the attic or ceiling. Lint settles in that first turn, especially when the dryer stops and lint in the vertical section falls back down. Every 90 degree elbow also reduces the allowed run length by 5 feet under section M1502.
Crushed or flexible duct in the cavity. Foil hose pushed into the wall during construction or a remodel is common. It flattens against studs, plumbing or electrical boxes and catches lint in every ridge. The code requires rigid metal duct with a smooth interior inside walls and ceilings.
Screws through the joints. The code prohibits screws or fasteners that protrude into the duct, but we still find them. Each screw tip catches lint, and over time a small ball of lint becomes a plug.
Joints installed backward. Rigid duct sections should fit with the male end pointing toward the outside. When reversed, each joint presents a lip that catches lint.
Disconnected duct. A joint that has pulled apart inside the wall blows lint and humid air into the cavity. In Florida’s humidity, that can mean damp drywall and mold behind the laundry room, plus lint sitting where a fire would start out of sight.
Long runs to a roof. Interior laundry rooms often vent up through the attic and out a roof cap. The vertical climb and the long length both give lint more chances to settle.
What a homeowner can safely do
- Clean the lint filter every load, and wash off any film from dryer sheets.
- Vacuum the lint filter housing with a crevice tool.
- Replace a crushed or vinyl hose with a short, listed metal transition.
- Clear the hood from the outside: pull lint out of the louvers and make sure the damper swings freely.
- Brush a rigid metal run with a dryer vent brush kit, turning the rods in the direction the kit specifies so the sections do not unscrew inside the wall.
What to avoid
- Do not force a brush past a hard stop. That is often a crushed section, a screw or a disconnected joint, and pushing harder can separate the duct or leave the brush head stuck.
- Do not run a drill driven brush through foil hose. It shreds the foil.
- Do not use a leaf blower from outside. It packs lint deeper and can blow joints apart inside the wall.
- Do not keep running the dryer while the vent is blocked. Restricted airflow means a hotter dryer, and the US Fire Administration identifies failure to clean as the leading cause of home dryer fires.
When the wall needs opening
| What we find | What it means | Typical answer |
|---|---|---|
| Brush stops at the same point every time | Crush, screw or broken joint | Open the wall at that spot and repair |
| Lint or moisture stains on the wall near the laundry | Leaking or disconnected joint | Open, reconnect or replace with rigid duct |
| Foil hose visible inside the wall opening | Concealed flexible duct | Replace with rigid metal |
| A brush head or object stuck in the run | Obstruction | Retrieve, then clean the full run |
Most clogs in a rigid run clear without opening anything. A dryer vent cleaning costs $100 to $200. We measure airflow at the outside first, then run a rotary brush and compressed air through the full run from both ends where possible, clear the hood and measure again.
When the duct inside the wall is damaged or the wrong material, that is a dryer vent repair at $200 to $600, with rigid metal duct and joints sealed in foil tape. A run that has to be opened is quoted before booking. If you want to know what is inside the wall before deciding, a dryer vent inspection traces the run. Our article on signs of a clogged dryer vent lists other symptoms worth checking, and you can book through our contact page.
