By Noah Sanders

If you’ve lived in San Francisco for any period of time, you’ve probably heard a horror story about mold in someone’s home. You’re familiar with tales of damp closets covered in spore-producing fungi. You’ve heard about Stachybotrys chartarum (or toxic black mold) causing asthma, headaches, and melancholic bouts of lethargy. You know of walls being removed and homes being evacuated due to full-on fungal invasions. Mold is a dangerous beast, and San Francisco can feel like its primary point of attack. Dig a little deeper, and what seeps to the surface is something a bit scarier: mold is a naturally occurring phenomena, and most plus-size cities are fertile breeding grounds for the stuff. 

Mold sucks, no two ways about it. But it is preventable, and if dealt with promptly and properly, is also completely manageable. So what is San Francisco doing wrong that so many of us are having problems with it? That answer ties back into this city’s current housing crisis.

The Horrors of Humidity

Molds are, to be frank, all over the place. The simple, microscopic organisms help break down dead stuff, plants and animals, and facilitate the reuse of their nutrients. To do so, mold fires an innumerous amount of spores into the atmosphere, which float along looking for the aforementioned deceased matter to sup on. Don’t panic, but everyone inhales an acceptable number of these spores, for the most part without any health issues. It’s only when mold is left unchecked in dank, dark climes, where it can multiply to high and potentially unhealthy levels, that it’s a problem. Mold’s a tricky beast; allergy levels can vary greatly between those exposed, with some unlucky folks actually developing allergies. Side effects to the fungal spores include mild hay fever, asthma, sinus infections, headaches, general depression, and a host of other respiratory maladies. If you see discolored or splotchy patches, if your apartment smells musty, or if your home has had past or recent water damage, chances are high that you’re living with mold.

As Karen Cohn, a program manager for the San Francisco Department of Public Health says, San Francisco is a particularly fertile environment for mold. “We are in a moist, humid environment. We have an extremely old housing stock– the fourth highest number of pre-1978 housing in the country – and in old homes, windows were single pane and walls were badly insulated.” That translates into hundreds of homes that don’t protect against the onset of moisture, a tantalizing petri dish for mold to form. I spoke to more than a few people in San Francisco who reported everything from a few splotches growing along their windowsill, to outbreaks getting so bad that they had to throw out mattresses and entire collections of vintage clothing.

Two years ago, John Wilson* moved into a Tenderloin apartment built in 1911, and learned about mold intrusion firsthand. “It was one or two months into living there and I couldn’t breath in my apartment,” he says. “Turns out I’m super allergic to mold, so we started moving things around in our closet and I was like, ‘Oh fuck.'” Wilson’s closet, which he described as feeling “wet” all the time, was covered in mold. “It was everywhere. On our clothes, our hats, our jackets. It was one of those moments where you feel like you’ve just lost the apartment contest.” He also suffered from a host of common mold issues – asthma, headaches, and lethargy.

San Francisco is one of the few cities in the country that places mold in the same category as rats and trash as a legal nuisance, and landlords can be liable if reported mold issues aren’t taken care of promptly. Wilson and his partner called their building manager, took pictures, and put in a work order for the apartment to be inspected and the mold removed. He also bought humidifiers, but the situation only worsened. “The apartment had no ventilation, and when we would cook, the moisture would just hang in the air,” he says.

At one point, the mold in his closet grew so bad that Wilson had to move all of his belongings into the main room, effectively cutting the small studio he was sharing in half. In the months after the mold had been reported, Wilson’s building went through a management change. After a year, he complained to the Rent Board and learned the new owners had no idea a work order had ever been filed. He was awarded three months rent and the management did what they could to remediate the mold. “We thought it was just in the closet, but it was everywhere. They tore down the walls and put in this special mold-resistant padding, re-sheetrocked the whole place, and in the end I actually ended up sleeping in that closet,” he says. When Wilson asked the workers removing the mold if the repairs would solve the problem, he was told they would eliminate the issue in the apartment, but that the mold was all over the building, so there was a potential for it to return. Almost a year later, when he was packing up to move to Oakland, Wilson saw the telltale multicolored splotches of mold.

Our Cramped City

If environmental dampness was the city’s only concern, the mold problem would definitely look less depressing. Cohn believes our issues are more than just damp climates and old buildings, they’re also economic and housing related. “We have a lot of overcrowding because of the cost of our housing,” she says. The Wall Street Journal reported in July that San Francisco had handily led the country in rent increases, with an average of 7.8 percent growth in rental prices, more than twice the rest of the nation. The average rental cost of a two-bedroom apartment in San Francisco teeters around $4,000 a month, and with the city considered one of the densest urban areas in the United States, it makes sense that more people are crowding into homes just to make rent. More people means more breathing, showering, and cooking (and creating condensation). Even worse, more roommates invariably mean more clutter, more beds, and more junk pressed up against walls. This creates tightly packed spaces where the extra condensation has nowhere to go, opening the door for mold to creep in along the edges. “Over-occupied homes have an additional moisture source,” says Cohn, “and that moisture has to go somewhere. If people aren’t opening windows, you’re going to have mold problems.” While Cohn hasn’t seen a major spike in mold-related inquiries in the last few years, she has seen increasingly more people relegating themselves to mold-infested living situations.

A tighter rental market increases fears that if someone loses their apartment, they won’t be able to find another affordable rental within the city. As Wilson says, “We were initially nervous to bring up our mold problem because we were worried that they’d choose to just remediate the whole building, and we’d get kicked out.” Even in San Francisco, where deferred maintenance of mold is just cause to sue your landlord, Wilson says, “If I had a place now that had really bad mold, I wouldn’t say a word. I’d keep my mouth shut.” Education about renter rights is an important part of mold remediation. Says Cohn, “People are scared of this subject. If something leaks and it isn’t taken care of, this is the property owner’s responsibility. Tenants need to feel empowered to ask for that.”

Growing Mold Together

Unfortunately, mold is an environmental surety. If you live in a city with a damp climate, the potential for it to spread is there. With education, prevention, and maintenance, mold becomes just another urban issue. But it’s also a symbol of the steadily changing nature of this city. San Francisco’s population is estimated to hit over a million people in the next 20 years (a million people spread out over a miniscule seven square miles). Rents are skyrocketing, and the ability of the middle and lower class to find affordable housing is becoming increasingly difficult. In effect, while shiny new condos are crowding out the skyline all over the city, the average renter is getting pushed down.

Which brings us back to mold. Sure, living with mold isn’t ideal, and no one really wants to do it, but on the other hand, with the rental market as it is, who can afford finding somewhere new to live? We fear mold because, yes, it can cause startling health effects and make for a shitty living situation, but some of us fear mold more because its presence indicates a reason we might be removed from our current living situations, regardless of how substandard they might be.


Mold proliferates with moisture, so preventing it means preventing dampness in your apartment. Cheryl Pearce, a certified microbiologist and owner of Mold Busters (an inspection and mold remediation business), recommends opening a window for five minutes every few hours to allow stagnant air out and cleaner, outdoor air in. If you have leaks or water damage, get them fixed as quickly as possible. If you think you have mold, call a recommended mold inspection company like Mold Busters, and make sure you get both an air test, a visual inspection, and a solid explanation of what you need to do to fix the current problem and to prevent the issue in the future.

*name changed upon request of the interviewee