The trio of young men hanging out in the murkily lit lobby at Vancouver City Hall on this warm July evening seemed displaced at first from their natural habitat, a craft-beer pub or nouveau-ramen restaurant.

But the three have forsaken other activities for a couple of hours to participate in a show of support for new rental and condo projects.

"This building will give 109 households the same opportunities I've had," 29-year-old Reilly Wood said when he got his chance to address city councillors, who were facing a series of public hearings about new projects that Tuesday.

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Mr. Wood, a software engineer who lives in a city-built apartment in the Mount Pleasant neighbourhood, was speaking in support of a proposed rental building nearby at Kingsway and St. George Street. "I welcome those people as my neighbours."

Brendan Dawe, a 25-year-old voter-outreach worker, later added his argument for a proposed 91-unit rental building on East Hastings Street, while 43-year-old technology worker Stuart Smith, the third attendee, watched and listened in preparation for being a speaker at a future meeting.

The three are part of a small but growing new group in Vancouver that is making an organized effort to show public support for new developments of all kinds, which they see as a key solution to the region's escalating housing crisis.

Among them is Karen Sawatzky, a Simon Fraser University graduate student who has highlighted the housing problems created by Airbnb in the city, and a random assortment of others who have met by chance.

They include one person who has worked with the NDP and another who is working the federal Liberals, but many are apolitical.

So far, they have shown up at the last three sets of public hearings on housing in Vancouver.

Their group, Abundant Housing Vancouver, is an unplanned participant in what has become an almost overnight social movement in dozens of American cities, where advocates have banded together to demand population density, more housing projects and less militant protection of single-family neighbourhoods.

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The city seen as leading that charge is San Francisco, where a former high-school math teacher named Sonja Trauss started a group called the San Francisco Bay Area Renters Association to lobby for more development.

But the idea has also popped up in such places as Iowa City, Cambridge, Mass., and Seattle.

Some of them call themselves YIMBYs (Yes in My Backyard), as the counter to groups that have become familiar sight in many high-growth cities, resident groups who oppose developments and are labelled NIMBYs (Not in My Back Yard).

The movement has grown so rapidly that a YIMBY conference last month in Boulder, Colo., drew representatives from more than a dozen cities, including one in New Zealand, and more than 200 national participants.

"You have a new narrative that's developing among progressives," said Sara Maxana, a leader in the Seattle for Everyone group, who was one of the key speakers in Boulder. "It used to be 'We need to charge developers for everything, we need to stop development.' But now we're saying when we put more barriers, that decreases supply and the cost of housing goes up. So we need to embrace it, but shape it."

Vancouver's group is just getting off the ground, with a website launched on Thursday and ongoing conversations over, yes, craft beers about where exactly everyone stands on support for which kinds of developments.

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They are not the first housing-action group that has launched in the city in recent years, as the rapid rise of house prices has created unprecedented stress. Other clusters of mainly young people have formed around the #donthave1million movement, Housing Action For Local Taxpayers, and Generation Squeeze.

For the first two, the impact of foreign capital on the housing movement has been a major focus and they have lobbied for information about the amount and controls or taxes to limit it.

Abundant Housing Vancouver does not discount that, but it has chosen to concentrate its energy on advocating for more supply – and supply that is not always squeezed into the slivers of land usually set aside for apartments in cities.

"Typically, the only place you can develop is where poor people live, like around Metrotown in Burnaby," Mr. Dawe said. "We'd see less of that if we didn't corral all the density there."

Mr. Dawe and others would like to see municipal councils be brave enough to start allowing denser development in the huge areas of land now set aside for single-family housing.

Danny Oleksiuk, a 31-year-old labour lawyer, said he was motivated to join up when he saw a map showing that 31 per cent of Vancouver's residents live on 83 per cent of the available land.

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"My interest is really in the single-family neighbourhoods, where it's now a $2-million entry price. There's a lot of land there and not a lot of people, but it's illegal to build affordable housing."

They have already been accused by some, in Vancouver's hyper-polarized environment, as being some kind of undercover agents for developers.

Mr. Oleksiuk dismisses that. "Where I live, I'd love to have another grocery store. If I lobby for that, no one would call me a shill for IGA."