FRANKFURT — A gray apartment block in Frankfurt, graffiti across the facade. Eight French balconies look out onto a three-lane road, with the Zeil shopping district just a short walk away. Harald Müller and Carsten Siebert approach the entrance. Müller snaps photos of the doorbells and mailboxes with a digital camera. “Collecting evidence,” Siebert says, pressing a buzzer. A faint buzz, the door opens, and they step inside. The stairwell is narrow, the air dusty, bags of plaster leaning against the wall.
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Müller and Siebert are housing security officers with Frankfurt’s Building Inspectorate. One is 57 but looks much younger, with sneakers and a pearl bracelet on his left wrist; the other is in his late 40s, wearing a black softshell jacket. “Housing detectives” is probably closer to the mark: Their job is to track down illegally rented vacation apartments. To be allowed to join them, Die Zeit had to agree not to use their real names. Their boss insisted on it, worried for their safety. Müller has already been threatened with a knife.
Like many big cities, Frankfurt is also suffering from a shortage of affordable housing. One reason is the conversion of long-term rental units into vacation flats. With the rise of platforms like Airbnb, it has been more lucrative for some owners to rent short-term than to commit to permanent tenants. Over the years, cities and tourist regions alike have responded with regulations. But how effective are they? And is the crackdown on illegal vacation rentals really easing pressure on the housing market?
Is the crackdown on illegal vacation rentals really easing pressure on the housing market?
On the second floor, a stocky older man appears from above, clearly uneasy. Through the thin walls, the hum of traffic seeps in from outside. He explains that he is the neighbor, the one who filed the report, and lives directly above the suspect apartment. At night, he says, he can only sleep with the window open. But below, the noise has been relentless, along with the smell of cannabis and shisha. He admits he agonized “a lot” over whether to say anything, since it felt like “snitching.” But then again: “Why should I have to breathe it in and listen to it?” He points them to the right door, then heads back upstairs.
That is often how it happens. Frankfurt has a dedicated reporting office. “A lot of people come forward when they see people constantly arriving with rolling suitcases or partying,” Müller later explains. But the inspectorate also tracks down violations on the rental platforms themselves.
In this case, they found the property listed on one of the biggest vacation rental sites. Siebert had spotted the ad: “Nice apartment – centrally located.” A studio for two, with a bed, bathroom and small kitchenette. Rating: 4.66 out of 5 stars. Price: 77 euros a night. Not bad for Frankfurt. But at a monthly rate, that comes to more than 2,300 euros: out of reach for a student or most people working in the city center. From an owner’s point of view, though, the math is clear: daily rentals are far more profitable than a long-term lease.
At the end of last year, the Fraunhofer Institute for Industrial Engineering released a study commissioned by Airbnb. It concluded that shared housing models make more efficient use of space, but do not significantly affect overall rent levels.
Signs of systematic short-term rentals
The picture changes when you look at the number of apartments. In Frankfurt alone, Müller, Siebert, and their colleagues have put 1,141 illegal vacation units back onto the regular rental market since 2018. That is equivalent to a large new housing project, says Marcus Gwechenberger, Frankfurt’s head of planning and housing.
“If we develop a new neighborhood with 1,000 apartments, it takes at least as long. Because they first have to be designed and then built,” he notes. Other cities report similar successes: since 2016, Berlin’s Friedrichshain-Kreuzberg district has reclaimed more than 2,000 vacation apartments. Munich, meanwhile, counted 246 last year alone.
Siebert rings the bell. Nothing. He knocks. The bell again. At last, a sound from inside. The door creaks open. A young man stands in socks and flip-flops. Though it is past 10 a.m., he looks groggy.
“Good afternoon, building inspector. Do you live here?” Siebert asks. The man looks confused. Switching to English, Siebert asks if he booked the flat through the same portal where he found the ad. The man hesitates, then nods. He pulls out his phone and shows the listing. It matches.
Like detectives, the officers probe further. How long has he been here? How long is he staying? He only arrived today and plans to stay for a week. Does he have a booking confirmation? The man shows it without fuss.
How did he get in? Has he met the landlord? He ducks back into the flat and returns with a small box, black with a numeric code lock. Inside was the key, he explains. The landlord had given him the code, but they never met in person. Such boxes are typical for professional short-term rental operators, but increasingly used by private landlords, too. Another sign no one actually lives there.
“We also have the online reviews, which are admissible in court”
The officers thank him and leave. The guest has nothing to fear, but the landlord certainly does. Outside again, Müller and Siebert look pleased. Encounters like this are a stroke of luck.
“We also have the online reviews, which are admissible in court. But witness testimony can carry even more weight,” says Siebert. Because you always have to be ready for a trial. Frankfurt has had a vacation rental ordinance in place since 2018. Permanent subletting of individual rooms is allowed, or the entire flat for up to eight weeks per year.
“We object to the systematic conversion of apartments intended as homes into tourist rentals,” says planning chief Gwechenberger. The goal is to ensure people can live and work permanently in Frankfurt — not just tourists, business travelers or tradespeople passing through. Anyone renting regularly to short-term guests in Frankfurt needs a permit. Without one, fines run up to 25,000 euros, and in especially severe cases, even 500,000 euros.
The work is still demanding. It is not as simple as getting a tip and showing up. A site visit only comes at the end, Müller says. The first step is building a full picture. He clicks through digital inquiry forms. He needs to establish what the property is officially registered as: Are the rooms designated for residential use? Or licensed as offices? A guesthouse? Or storage?
Not everyone opens the door
This is decisive for how a case is handled. It may turn out that the apartment has a permit for vacation rental. Then the matter is settled quickly. But sometimes officials have to act fast, for instance if there is no fire escape.
“If we know about it, we are obligated to step in,” Siebert says. “And besides, you could hardly sleep at night yourself.”
Some permits date back to the 1950s, and certain documents are still written in Sütterlin script, an historical form of German handwriting taught in schools until 1941. Others were lost or burned during World War II. In such cases, Müller combs through the city archives, hoping to find something. If he does, it is rarely digitized. Then he has to sit in the reading room and work through paper files.
These are lovely houses. Families could easily live there.
Some cases drag on endlessly. On the fourth floor of the Frankfurt Building Inspectorate, you get a sense of this, reminiscent of investigations into organized crime. A colleague of Siebert and Müller points to a tall filing cabinet stuffed with folders. All of it belongs to a single case, she explains. It has been going on for two years. A company owns 10 properties in Frankfurt and rents out beds to construction workers or temporary staff. The business brings in six-figure sums each month. She shows photos she took during an inspection. These are lovely houses, she says. Families could easily live there.
“The trend now is toward entire buildings being taken over by different companies and converted into worker housing,” Müller adds. Such cases make up about half his workload, he estimates. The rest usually involve unsuspecting private individuals who take down their listings as soon as the inspector makes contact, or who go on to apply for a permit after all.
Sometimes, though, nothing happens. “We have a few like that, and we know they coach their guests,” Müller says. When they ring the bell, no one answers. “Then you’re left standing there like a drowned rat.”
Their next stop takes Müller and Siebert to an apartment block in the Gallus district, a short walk from the central station. Here, too, they suspect an illegal vacation rental. Three black key boxes are fixed to the rainwater pipe. They say they have tried six times already to find someone at home. According to the online booking calendar, the apartment should be occupied today. The doormat greets them with the word “Welcome.” They ring the bell. Silence.
