America's southern states are facing a silent epidemic that is decimating home values and putting owners' health at risk.

Mold has long plagued homes in warmer climates, causing ailments ranging from asthma, coughs and shortness of breath to bronchitis, allergic rhinitis and eczema.

But an explosion of new housing, rapidly constructed to combat a longstanding housing shortage, has sparked thousands of mold-related insurance claims and social media complaints from homeowners – and they could erode the housing market even further.

Particularly in Florida, which has been at the center of America's post-Covid homebuilding boom, new residences materialized quickly as cost-conscious buyers from New York and California moved in.

The state accounted for nearly 12 percent of all new-home construction permits issued nationwide in 2024, according to Realtor.com, making it one of the country's busiest markets for residential development.

Florida's new-build communities have raised concerns among experts ranging from poor ventilation to excessive indoor humidity – conditions that can create an ideal breeding ground for mold.

Dr Daryl Gioffre, a gut health specialist and mold toxicity expert based in Naples, Florida, said what makes mold so worrisome is its often 'invisible' nature.

'One of the biggest misconceptions is that mold is only a problem in older homes,' Gioffre told the Daily Mail. 'Some of the sickest mold patients I've worked with were living in brand-new homes.'

Frustrated social media users have dubbed it 'the mold pandemic,' and one expert said he would 'absolutely' liken its damage on the market to that of the condo crisis.

An estimated 47 percent of homes across the US have dampness or mold, according to Berkley Lab's resource bank and a 2022 NIOSH report.

Common sources of mold across the country include leaks (roofs, walls, plumbing), environmental factors (flooding from a major water event that leaves your carpet or wood soaked) and condensation (poor bathroom ventilation after a hot shower), among others.

But in southeastern states, humidity and structural issues are king.

In Florida, where humidity hovers at around 70 percent on average, close to 75 percent of homes in the state have mold, according to Palm Build Restoration.

Mold damage can be rectified, but it becomes a question of how far the homeowner is willing to go.

Sam Hickerson, who runs the mold remediation resource site restoreadvisor.com, told the Daily Mail that costs to fix mold in humid Southern states typically runs $1,500 to $6,000 for moderate cases. So, some owners opt to sell instead.

For buyers, Bob Miller of Millshire Realty told the Daily Mail that one of their biggest concerns shouldn't necessarily be the mold itself – it should be the cause.

'Recurrence is extremely common when the underlying moisture source isn't addressed,' Hickerson told the Daily Mail. 'Most homeowners who see it come back, it's because they missed a slow leak or inadequate ventilation.' 

'While not all mold is a major issue, black mold can create health concerns and significant property damage if left unaddressed,' Miller explained. 'Areas with high humidity, heavy rainfall and deferred maintenance tend to see these problems more often.'

Victoria Shtainer, an associate broker in New York and Florida, told the Daily Mail that mold has always been a 'huge risk' for homebuyers, with states like Florida and Louisiana being particularly dangerous.

'These states have high humidity, rain and hurricanes,' Shtainer added. 'Inspection is a must prior to buying a home in these states.'

Warm, muggy conditions create the perfect environment for the fungus. And in the quickly constructed houses, builders often prioritized speed over air quality, according to 100 Mile Home Inspections, leaving too many opportunities for mold to invade.

Mold can begin forming on porous materials within 24 to 48 hours under normal conditions. In South Florida condominiums, where humidity often reaches 70 percent and air conditioning runs year-round, growth can occur in as little as 12 to 24 hours. 

The average relative humidity in the country's most humid cities – including Lake Charles, Louisiana, Gainesville, Florida, Jackson, Mississippi, and Port Arthur, Texas – regularly reach 90 percent, according to 2025 data from NOAA.

And with the nearly five million new homes that went up between 2020 and 2023 mostly in the South and West, per a Stateline report, their residents were handed a welcome basket of related issues.

Construction expert Phil Adkins told the Daily Mail that new homes can actually be more prone to mold than older ones because 'newer builds are intentionally built tighter.'

'They are sealed and insulated for energy efficiency, which is great for your utility bills, but it also means less air flow than older and draftier builds,' Adkins explained. 'It also means that when moisture gets in, it has fewer ways to escape. That trapped humidity is the perfect environment for mold.

'New construction materials, like lumber, concrete and drywall, also carry a lot of built-in moisture that takes time to go away.'

Adkins said that in communities where demand is high, there's a rush to get new homes built, which means materials may not have the chance to properly dry off before being assembled.

Still, older buildings can pose just as big of a risk.

There's the possibility of widespread water damage, leaking roofs, aging plumbing systems and decades of deferred maintenance – all of which can create ideal conditions for mold growth, and have been uncovered during Florida inspections as of late.

Since the Surfside condo collapse in 2021, houses and buildings across the state have been facing added challenges when it comes to keeping homes up to code. 

Stricter condominium inspection requirements were introduced after the building collapse, consequently triggering sky-high costs for anyone wanting to hold onto their homes.

In worst-case scenarios, homeowners can face remediation costs amounting to tens of thousands of dollars.

California homeowner David Vivero told the Daily Mail that renovations at his mold-infested property cost as much as $800 per square foot after the contamination spread throughout the house.

And for homeowners like him, consequences extend beyond property damage.

Black mold linked to ongoing water intrusion can create serious health concerns if left untreated. 

By the time he discovered mold in his home, Vivero – who was in his 30s – had been diagnosed with kidney cancer. His wife's kidney function began declining, and his five-year-old son experienced neurodevelopmental challenges and anxiety. 

After repeatedly being told there was no mold problem, a pediatrician recommended mold testing – levels of concern were then found in Vivero's blood and urine. The family eventually discovered mold that had started in a wine cabinet and spread throughout their home.

'Once we started peeling back the layers of the house, we discovered it had spread everywhere,' said Vivero, who has since created a company aimed at helping homeowners test and monitor for mold and bacteria.

When inspections uncover structural problems, owners can face bills for tens of thousands of dollars. For some retirees or fixed-income owners, selling their home altogether becomes the more affordable option.

But getting out of a mold-laden house isn't as easy as listing it on the market.

If mold is discovered in a property, the home's resale value can drop pretty drastically – up to 37 percent, according to Ruby Home.

The data shows that as many as half of potential buyers back out of a deal once they learn a property has had a mold problem, even if it's already been fixed.

Insurance coverage can also be a major issue.

In 2022, approximately 264,000 mold-related insurance claims were filed in Florida, accounting for more than 20 percent of all homeowners insurance claims in the state. 

In most cases, standard homeowners insurance usually excludes mold, making it a required add-on. It's sometimes referred to as hidden water damage or water backup coverage, with payouts ranging anywhere from $5,000 to $50,000 depending on the state and type of coverage.

In Florida, adding the optional mold coverage typically costs between $500 to $1,500 per year, depending on the home's risk level and the coverage limit, according to Way Better Insurance.

But even then, mold insurance claims can be denied if the mold develops from something fixable. 

For example, if someone finds mold that was caused by a leaky pipe, their policy may not cover the damage because, technically, it's considered a maintenance issue. 

While experts are seeing the crisis concentrated around the Southeast, it could spread to other areas where high humidity, heavy rainfall and deferred maintenance create ideal conditions for mold growth. Coastal communities across the country are particularly vulnerable because moisture exposure is harder to control and maintenance costs are often higher.

'Florida's combination of heat, humidity and hurricane exposure makes it one of the hardest states in the country to keep mold at bay,' Hickerson said.

Not all states are hit as hard.

Areas with dry, desert-like climates, including Nevada and Arizona, have some of the country's 'least moldy' homes, according to American Home Shield.

Still, experts say they wouldn't count the fungus out completely, recommending thorough inspections before settling somewhere new.