From the outside, the 1975 Hino KL looks like a regular truck, discreetly parked week-round in East Vancouver. But this truck is anything but ordinary. Every weekend, it becomes a place of gathering for the city’s growing underground sauna community—a community that, according to Adrian Sinclair, co-founder of Transformation Projects and a sauna veteran, has existed for over a decade.

Inside, the truck is equipped with a sauna room that can fit up to 15 people, in addition to a lounge area where regulars can relax before or after their sweat.

“It all started in 2001, when Karlis Kalnins, the originator of this whole thing, built a sauna in a truck and drove it up to the Intention Festival for New Year’s Eve,” Sinclair says. That Sunday, Kalnins invited a few people for a sweat. He did it again the next week and the week after that. Fourteen years later, the weekly sweat has becomea regular weekend activity for many.

Sinclair and Kalnins met in 2005 and started working together to scale up the concept of mobile saunas.

Four years ago, they created the BC Mobile Sauna Society to keep up with the growing community. Today, the non- profit operates two mobile saunas in Vancouver and one in Gabriola Island.

The location and time of the weekly sweat is not advertised anywhere. To join, you must be invited by someone who’s already been to the mobile sauna.

“For example, if I invite you and you come to the sweat, next weekend you can invite someone else. That’s how the community grows, but at the same time stays familiar,” explains Sinclair. There’s no fee to participate, though donations are highly encouraged.

The trucks usually stay parked in one location for roughly six months. “When you stay this long, you are able to create communities that continue to come to the weekly sweats even after the bus moves away,” Sinclair says.

The weekly sweat brings together a diverse crowd. Twenty-year-old university students sit in the steam with 65-year-old retirees.

“A lot of times, when people get invited, they are hesitant. They don’t want to be naked in front of people they’ve never seen before,” Sinclair says. “But I can’t count how many times someone’s come up to me and told me how glad they were they had come.”

On some nights, the steam involves singing. Other times, it’s just about nice conversations with familiar strangers. Whatever it is, there are always plenty of opportunities for shared experiences. That’s why Sinclair believes people keep coming back, every weekend, for years.

“The sweat changes people. You get to talk to people who are not in your social milieu and connect with someone on a deeper level,” he says. “And that’s pretty unusual in our society because everyone lives in a niche. It’s a way to rewire yourself and get into a more calm space in your mind.”

Inspired by the potential of the trucks hold as community-building spaces, Sinclair decided to start up a commercial version of the mobile sauna that could be rented by companies, organizations or small groups of people.

Last year, his event production business, Transformation Projects, bought a 1985 Thomas Built Bus and completely refurbished it. They added a sauna and a lounge. The bus already had a stove, four burners, and a fridge, all of which run on propane.

“With the Sauna Bus, we are trying to strike a balance between making a living, and at the same time maintaining strong community standards,” says Sinclair. Today, the bus is available for rent at $250/hour.

Sinclair believes whether it’s yoga class, a run, or the weekly sauna, it’s important to have activities that people engage in regularly.

“The weekly sweat is powerful not just because it’s a sauna or because it’s interesting and weird. It’s also powerful because it’s weekly. There’s something to be said for that,” he says.

“Once you’ve made that emotional commitment, you can’t avoid it...these are the activities that help connect with people without you realizing it.”

For more information on the Sauna Bus, see Saunabus.Tumblr.com