Bathroom walls showing signs of moisture?

I am not sure I am asking the question in the correct section of the site, but i started noticing in our master bathroom that the walls seem to be "moist". I am not sure that is the correct terminology, so I am including a picture for reference.


Hopefully you will be able to see the it in the picture. The exhaust fan seems to work fine, i tested with a piece of toilet paper and it attaches to the outside grill of the vent, showing there is somewhat of a suction.

Can you provide any feedback whether this could be a problem and how i might address it?

Thank you

 

Highly likely from humidity from showers. If you don't run (or don't have) an exhaust fan, then the moisture has no place to go, deposits itself on the ceiling and walls and runs down. Exhaust fans should run possibly up to 30 minutes after you leave the shower to evacuate all the hot moist air.

 

Are your mirrors all steamed up after you get out of the shower? The stains may be residual from previous use. You use the fan, but does everybody that uses the bathroom faithfully turn the fan on when using the shower or bath. My wife is famous for steaming the outer layer of skin off her body with each shower, I finally convinced her to dial the heat back some.

 

The fan also needs to stay on until the steam is gone, NOT until the person leaves the bathroom. I've seen people add circuits so the fan stays on 5 minutes after the light is turned off.

Also holding up a piece of toilet paper indicates very little suction, just that there is some. Will it hold a piece of letter paper? Where does the fan duct to, maybe you could see if it's clogged.

 

The minimum fan flow should be 50 cfm, and most older fans don't make that level. They also make special switches for bathroom fans that will turn on the fan when needed, but remain on for an adjustable period of time when the fan is turned off. This allows people to leave when done and turn the fan switch off and the fan will then turn off after the preset delay time.

Bud

 

Answering some of the questions, the fan lists 50 cfm. I did test with an A4 sheet of paper and the fan did hold it. Only a piece of toilet paper. I am also going to buy a humidity sensor as advised. Finally I know the biggest issue would be mold, is there a way to detect if I do already have mold without ripping the drywall?

Thank you for all the help

 

Is the moisture only apparent after taking a shower or bath? Is it more apparent during the cold or warm season? It looks like surface moisture as opposed to latent moisture from inside the walls. As others have said, keep the fan on for longer periods and start the fan before showering. Keep door open after showering and let dryer air from rest of house blend in. Make sure everybody pays attention to the fan rules. Also try and limit shower use to no more than 15 minutes. Anything longer is a waste.

 

Just one correction. It did NOT hold the A4 sheet. The moisture as you see on the picture is apparent at any time, but worse after shower

 

Can you hear the damper open and close when using the fan? Sometimes, you hear a light "clunk" after you turn the fan off which is the damper closing. It may be stuck closed or restricting air flow. Have you verified that you are getting good flow out of the roof or eaves (or where ever the vent exits)?

 

50 cfm is extremely small. 100 cfm should be the minimum for even the smallest of bathrooms. If you have no mold on the wet side of the sheet rock then you will have none on the dry side. As stated bath fans must run at least 20 minutes after showering to remove the RH. With only a 50 cfm fan id say an hour.