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I have a popcorn ceiling in my bathroom that has a tendency to collect mold. I clean it off with bleach but it always comes back. There was no mold prior to remodeling the bathroom a few years ago, which is strange since the remodeling removed wallpaper and leaky tiles that I would've thought would increase mold production. There is a vent in the bathroom in addition to the recently upgraded bath fan, so it has plenty of ventilation. What is making the ceiling such a cozy place for mold in the otherwise clean and well-ventilated room?

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    A "popcorn" ceiling is probably not the best choice for a location like this. Have you considered removing it and using a different covering?
    – jwh20
    Dec 29, 2020 at 17:50
  • Or just paint it. Acoustical texture isn't initially sealed very well.
    – isherwood
    Dec 29, 2020 at 17:56
  • And mold doesn't grow where there isn't moisture. Your bath fan isn't doing the job or something else is introducing water to that location.
    – isherwood
    Dec 29, 2020 at 17:57
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    I have seen bathroom remodels where a new door or a new floor was installed that reduced the air gap at the bottom of the door. A tight seal will keep the nice new fan from moving air with the door closed.
    – Ed Beal
    Dec 29, 2020 at 18:13
  • Could also be because the new shower is more powerful. I've seen this before where the new 'power' shower delivers way more water which means more 'steam' to condense on cooler spots.
    – handyman
    Dec 29, 2020 at 19:53

2 Answers 2

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The root cause of the reoccurring mold was not the ceiling, but the walls. There is a decorative ring of dark colored tiles at the top of the shower, and these were hiding mold. Deep cleaning the tiles near the ceiling has prevented the mold from coming back.

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Did you put in the new bath fan after the rest of the remodel? If the new ceiling was up for even a few days before you got your ventilation system up and running, there’s a chance that mold could have started growing then. It only takes 24-48 hours for mold to start growing (https://www.fema.gov/pdf/rebuild/recover/fema_mold_brochure_english.pdf). Popcorn ceilings are porous enough that mold can penetrate them very easily.

The big problem is that you’re using store bought bleach. On porous material, household bleach only kills surface mold, and the water in it actually ends up feeding the roots of the mold. I learned this the hard way - I was using bleach to try and clean up some problem spots too and couldn’t figure out why it wasn’t taking care of the problem. I finally ended up having to hire a remediation company. And they explained to me why my bleach hadn’t worked. Here’s some more info on this, if you’re interested.

Bleach works really, really well on surfaces that aren’t porous. It will basically kill every kind of mold that it touches. But the chlorine (sodium hypochlorite) in chlorine bleach is going to keep it from penetrating past the surface of a material that’s porous. (https://moldandairductpros.com/using-bleach-to-remove-mold/) That’s it’s job. So when you use bleach on a surface like popcorn ceiling, you’re removing the visible mold, but the roots of the mold are left completely untouched. But wait, it gets worse. The roots of the mold are left untouched by the bleach… but Clorox bleach is made of “mostly water and sodium hypochlorite” (https://www.clorox.com/learn/what-is-bleach-what-are-active-ingredients/)… and water will definitely penetrate a porous surface. What’s mold love more than water? So when you use bleach on your ceiling, not only is the chlorine failing to kill the mold below the surface, but the water is feeding it.

I know this is a really old post, and you’ve definitely figured out your bathroom mold situation by now, but for anyone else in a similar situation, I’d probably say that your best bet is to get a professional to handle any kind of serious, stubborn moldproblem. Especially dealing with a porous material. I know it can be pricey, but you might end up having to hire pros after trying to DIY anyway (like I did.) Also, removing the mold at the root level will probably involve some amount of remediation that could go wrong if you don’t know what you’re doing. And you could even end up disturbing the colony and spreading the mold to other parts of your house. If you decide to tackle it yourself, make sure you really read up on proper PPE and how to use barriers to keep spores from spreading. This is a useful site with general info about remediation, and it’s got good advice on PPE and containment: https://ehs.ncsu.edu/occupational-health/indoor-air-quality/mold-remediation-guidelines/ Good luck! Hope this is helpful to someone!

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