Bathroom mold

[Scouter]

A few years (5+) ago we replaced our bathroom tub and surround, this year the caulking developed mold. We have a fan and we keep it running 30-60 minutes after the bath/shower. Is this something normal? Does caulking always develop mold? Should the fan prevent it?

[EightFingers]

What type of caulk did you use?

[Scouter]

What type of caulk did you use?

Whatever the professionals used when they installed it. I assume they know what they're doing, bathroom remodeling is their primary business.

[Snipe Hunter]

Replace the Caulk. I've learned over the years to buy good caulk for a variety of reasons. Cheap painter's caulk shrinks and cracks. Cheap silicon caulk or "paintable"  silicon caulk contains some latex or other "polymers" in it to make it spread easier and adhere to latex paint. But don't do much to prevent mold. Step up and buy 100% Silicon caulk. It should say "Bathrooms" or Kitchens" on it.  No caulk lasts forever and most don't have any mold inhibitors in it. Look for "Meets ASTM C-920, Class 50" on the label. GE Supreme Kitchen and Bath has the mold inhibitors and very high adhesion properties and Meets ASTM C-920, Class 50. There are several GE Supremes. This should be a black tube. You might not find it in the big box stores. One GE Supreme is paintable and will have "Hybrid" on the label. This isn't the one you want. You'll find the the mold inhibitors are usually wax. Don't let that scare you. It works.

I'm sure there's other brands that meet ASTM C-920, Class 50 but I haven't used them.

You want this one.

I don't think I paid this much but here it is. I think I paid about $10 a tube. Amazon

[Scouter]

Replace the Caulk. I've learned over the years to buy good caulk for a variety of reasons. Cheap painter's caulk shrinks and cracks. Cheap silicon caulk or "paintable"  silicon caulk contains some latex or other "polymers" in it to make it spread easier and adhere to latex paint. But don't do much to prevent mold. Step up and buy 100% Silicon caulk. It should say "Bathrooms" or Kitchens" on it.  No caulk lasts forever and most don't have any mold inhibitors in it. Look for "Meets ASTM C-920, Class 50" on the label. GE Supreme Kitchen and Bath has the mold inhibitors and very high adhesion properties and Meets ASTM C-920, Class 50. There are several GE Supremes. This should be a black tube. You might not find it in the big box stores. One GE Supreme is paintable and will have "Hybrid" on the label. This isn't the one you want. You'll find the the mold inhibitors are usually wax. Don't let that scare you. It works.

I'm sure there's other brands that meet ASTM C-920, Class 50 but I haven't used them.

You want this one.

I don't think I paid this much but here it is. I think I paid about $10 a tube. Amazon

Makes me feel better, that is what I bought at our local plumber's supply company.

[Cooler]

I used to have a mold problem with my shower.  I now leave the shower door open for an hour or so after using it to allow it to quickly dry out.  I have not had a repeat in the last 18 years.

The fan alone might not dry out the shower if the door is closed.

A very slow (but safe) way to clean the mold is to spray it with hydrogen peroxide.  It takes about 10 applications over 10 days, but no odors or dangerous chemicals.

[joe1086]

FWIW if you recaulk....

You also don't want a deep gap full of caulk. Thick caulk applications are less flexible than thinner ones and that's why many fail. Water gets behind failed caulk, doesn't dry and mold results. Use a foam backer rod if the gap is deeper than the tile depth. Borgs have it but not in all sizes. I think I got 100' of it for $5 or $6 delivered on Amazon.

[brianwelch]

Best caulk I have ever used is a polyurethane. It was 2 part, exterior application on my windows,  installed by a pro, but 15 years after it was installed, I still could not peel it cleanly or cut thru it with a razor knife, it was so elastic...
I am sure federal/EPA guidelines have made the recipe such that the current product is nowhere near as good...

[mike4244]

A few years (5+) ago we replaced our bathroom tub and surround, this year the caulking developed mold. We have a fan and we keep it running 30-60 minutes after the bath/shower. Is this something normal? Does caulking always develop mold? Should the fan prevent it?

You can eliminate the mold and prevent it from appearing with Clorox household bleach. I keep a spray bottle in the bathrooms and spray about bi-weekly. I spray with the ceiling fan on because the bleach does have an unpleasant odor. Takes 30/40  minutes to disperse the odor. 
Usually the mold is gone in 24 hours. Been doing this 10+ years or more and mold has not re-appeared.
mike

[Scouter]

You can eliminate the mold and prevent it from appearing with Clorox household bleach. I keep a spray bottle in the bathrooms and spray about bi-weekly. I spray with the ceiling fan on because the bleach does have an unpleasant odor. Takes 30/40  minutes to disperse the odor. 
Usually the mold is gone in 24 hours. Been doing this 10+ years or more and mold has not re-appeared.
mike

Good idea. Clorox made a device you hung in the shower, after the shower press a button, closed the curtain/door, and it sprayed a scented bleach. Worked well for years, then they discontinued it.