Water dripping from a bathroom fan is one of those problems that tends to get ignored longer than it should. It often starts as a small drip after a hot shower, easy to assume it will dry out on its own. But the water has to be going somewhere, and in most cases, it is going into your ceiling cavity, onto the drywall, or along the duct and into the wall framing above.
In Vancouver’s climate, where the air is consistently damp from October through April, and temperatures drop enough at night to create condensation inside uninsulated ductwork, bathroom fan leaks are genuinely common. Many homes built in the 1970s and 1980s have exhaust fans that were installed without proper duct insulation, or worse, fans that vent directly into the attic space instead of to the exterior. Both situations cause chronic moisture problems that go far beyond a dripping fan cover.
Before you try to fix anything, there is one question worth answering first.
Condensation or Actual Water Intrusion?
The fix for a leaking bathroom fan depends entirely on where the water is actually coming from. Two very different causes look identical from inside the bathroom.
Condensation happens when warm, humid air from your shower travels through the exhaust duct and hits a cold surface inside the duct or at the vent cap. The moisture in the air condenses into water droplets, which then run back down the duct and drip through the fan housing. This is the more common cause in Vancouver homes, particularly in winter when the temperature difference between bathroom air and the uninsulated duct above is significant.
Actual water intrusion means rain or outside moisture is entering through the roof vent, damaged flashing, or a compromised vent cap, and traveling back down the duct into the fan. This type of leak often shows up or gets worse during or after rain, not just after showers.
To tell the difference: if the dripping only happens after hot showers and stops within an hour, condensation is the likely cause. If water appears during or after rainfall, regardless of whether anyone showered, the problem is outside at the roof vent or flashing.
Signs Your Bathroom Fan Is Causing Water Damage
You may already be past the “dripping fan” stage without realizing it. Watch for these indicators:
- Water stains on the ceiling around the fan are usually yellowish or brownish. These stains expand over time and indicate that moisture has been saturating the drywall repeatedly.
- Paint is bubbling or peeling near the fan. The moisture pushes through the ceiling material and breaks the paint’s bond from behind.
- A soft or sagging area on the ceiling around the fan. This means the drywall has absorbed enough water to lose structural integrity. At this stage, you are dealing with damage, not just a nuisance.
- A persistent musty smell in the bathroom even after it dries out. This is almost always a sign that mold is already growing somewhere in the ceiling cavity or ductwork, not just surface moisture.
- Dripping sounds inside the duct when the fan runs, or water visible on the fan cover or grille after showers.
Fixing a Condensation Problem
If condensation is the cause, the solution is to reduce the temperature difference the air encounters as it travels through the duct.
Insulate the ductwork: This is the most effective fix for condensation-related leaks. The duct carrying warm bathroom air should be wrapped in foam or fiberglass duct insulation along its entire length. Without insulation, the duct wall acts like a cold glass on a humid day. Moisture condenses on the inner surface and runs back toward the fan.
Check the duct slope: The duct should slope slightly downward toward the exterior vent so that any condensation that does form drains outward rather than back toward the fan. If the duct sags in the middle or runs flat, water pools and eventually finds its way back through the fan.
Check how the duct is vented: In many older Vancouver homes, bathroom fans were installed to vent into the attic rather than to the outside. This is not up to current code and creates chronic moisture problems in the attic on top of the condensation issue at the fan. If your duct terminates in the attic rather than at an exterior wall cap or roof vent, this needs to be corrected.
Run the fan longer: Running your exhaust fan for at least 20 minutes after showering removes the bulk of the humid air before it has a chance to condense in the duct. Many homeowners turn the fan off as soon as they leave the bathroom, which leaves the duct full of humid air to cool and condense.
Upgrade the fan if it is undersized: Fan capacity is measured in CFM (cubic feet per minute). The general rule is 1 CFM per square foot of bathroom floor space. An undersized fan does not move enough air to actually clear moisture before it condenses. If the fan has been in place since the 1980s or 1990s, it is likely both undersized and aging.
Fixing a Rain or Roof Vent Problem
If the water appears during rainfall rather than after showers, the problem is at the exterior and needs to be addressed from the outside.
Inspect the roof vent or wall cap: The exterior vent where the duct exits should have a cover that opens when the fan runs and closes when it does not, keeping rain and pests out. If the flaps are stuck open, broken, or missing, rain can enter freely. Replace the vent cap if it is damaged.
Check the flashing: If the duct exits through the roof, the flashing around the vent penetration can crack or lift over time, particularly after freeze-thaw cycles during Vancouver winters. Water that gets under the flashing travels down the duct and appears as a fan leak inside the bathroom.
Look for missing or damaged caulking: Look for the signs around the roof vent perimeter. Re-caulking with roofing-grade sealant is a straightforward fix if the flashing is otherwise intact.
For any work on the roof itself, a licensed roofing contractor is the right call. This is not a DIY situation if you are not comfortable on a roof, and getting it wrong means continued water entry.
When the Fan Has Already Caused Water Damage
If you have water stains, soft drywall, or a musty smell that has been present for more than a few days, the problem has already moved past a leaky fan and into structural moisture territory. The ceiling drywall may need to be opened to check how far moisture has spread into the framing and insulation above.
In Vancouver’s humid climate, mold can establish itself inside a wet ceiling cavity within 24 to 48 hours. If you can smell that distinctive musty odor, mold is almost certainly already present somewhere in the assembly above the fan. Surface cleaning does not address mold that has grown on framing or the back of drywall. That requires proper remediation. If mold has been detected or is suspected, USA Restoration’s mold remediation team can assess and treat it safely before repairs begin.
Prevention Habits That Actually Help
A few consistent habits dramatically reduce the chance of this problem recurring:
Run the exhaust fan for the full duration of your shower plus 20 minutes afterward. A timer switch or a humidity-sensing fan makes this automatic.
Keep the exterior vent clear. Check the outside vent cap seasonally, especially in autumn when debris and leaves can lodge in the flap and hold it partially open.
Feel the duct during winter if you have attic access. If the outside of the duct feels cold to the touch, it needs insulation. This is usually a half-hour job with basic materials from a hardware store.
Check the ceiling around your fan twice a year. A quick look for new staining, bubbling paint, or soft spots catches problems early before they require major repairs.
Frequently Asked Questions
Why does my bathroom fan drip water after a hot shower?
This is almost always condensation. Warm humid air from the shower travels into the exhaust duct, hits a cold surface inside the uninsulated duct, and turns back into water that drips through the fan. Insulating the ductwork and running the fan longer after showers solves most cases.
How do I know if my bathroom fan is leaking condensation or rain?
If water only appears after hot showers and stops within an hour, it is condensation. If water appears during or after rainfall, regardless of shower use, the problem is at the roof vent, vent cap, or flashing, and needs to be fixed from the outside.
Can a leaking bathroom fan cause mold in the ceiling?
Yes, and fairly quickly. In Vancouver’s climate, consistent moisture in a ceiling cavity can lead to mold growth on drywall and wood framing within 24 to 48 hours. A musty smell coming from the fan area is usually the first sign that mold is already present above the ceiling.
What CFM rating should my bathroom exhaust fan be?
The general guideline is 1 CFM per square foot of bathroom floor space, with a minimum of 50 CFM for any bathroom. Older fans installed decades ago often fall well below this, which means they cannot clear moisture fast enough to prevent condensation buildup in the duct.
Is it okay if my bathroom fan vents into the attic?
No. Venting a bathroom fan into the attic is not up to current building code and causes moisture problems in the attic over time. The duct should terminate at an exterior vent cap on an outside wall or through the roof. If yours currently vents into the attic, that needs to be corrected.
How long should I run my bathroom exhaust fan after a shower?
At least 20 minutes after you finish showering. Running it only during the shower is not enough time to remove the moisture from the air in the room and the duct. A timer switch or a humidity-sensing fan can automate this without any effort.
Conclusion
A dripping bathroom fan is almost always either a condensation problem or a rain intrusion problem, and the fix is completely different depending on which one it is. Getting that diagnosis right first saves you from addressing the wrong thing and watching the leak continue.
For most Vancouver homes, condensation is the culprit, and insulating the ductwork, combined with running the fan longer, solves it cleanly. If the water comes in during rain, the issue is at the roof vent or flashing and needs to be addressed from the outside. Either way, if there are already water stains or a musty smell in the bathroom, the damage inside the ceiling needs to be checked before repairs are made. Water that has been sitting in a ceiling cavity for any length of time in the Pacific Northwest does not dry on its own.