It’s been a decade since Denver began allowing developers to build on tiny lots near neighborhood urban centers without providing off-street parking, but only one new building has taken advantage of that exemption.

That’s about to change. And as the city’s development boom targets smaller and smaller spaces to shoehorn townhomes and micro-apartments, City Council members and some neighborhood activists worry that developers soon will exploit the parking exemption in a big way.

The council this week advanced a moratorium that would pause the parking exemption for some potential developments so the city can tighten the rule this fall, potentially to limit how big new buildings could be without providing parking. The exemption applies to small lots, defined as 6,250 square feet or less, in mixed-use zoning districts.

“There are tons of these opportunities on old South Pearl Street where all of a sudden, it could be row after row of 16 units with no parking, where it used to be single-family homes” or shops, Councilman Jolon Clark said. He represents south Denver and spoke in favor of the seven-month moratorium during Wednesday’s meeting of the Neighborhoods and Planning Committee.

Clark noted one proposal that has a developer eyeing exactly that — to build 16 housing units on a lot with just 50 feet of street frontage — to replace an old house within a block of Sushi Den. That is along one of Pearl Street’s most parking-choked stretches, and the developer is proposing to include just six off-street parking spaces, well below what would be required by the city’s minimum parking ratios if it was built on a larger lot.

“That is something that will dramatically change the feel of that community,” Clark said.

Among a half-dozen developments in the pipeline that qualify for the parking exemption is Pando Holdings’ plan to build two micro-apartment buildings on small side-by-side lots on Humboldt Street south of 16th Avenue. Its site development plans say each building would have 54 studio apartments, with no parking proposed — an idea that has ruffled some feathers in the neighborhood.

Another proposed project calls for two side-by-side buildings with a total of 43 units and no parking near Stout and Downing streets in Curtis Park, the city’s planning department says. The Landmark Preservation Commission rejected the first design, and a new concept design is underway, a department spokeswoman said.

The moratorium, which the committee advanced via voice vote to the full council, wouldn’t necessarily stop those in-the-works projects from proceeding, but it could force a pause for other budding plans for housing or, potentially, commercial buildings. The council likely will consider the moratorium by late next month.

If passed, it would expire March 31, or sooner if the council approves a zoning text amendment modifying the exemption.

Underlying the discussion of the moratorium, which grew in part out of a focus group convened by outgoing Councilwoman Jeanne Robb early last year, is a growing tension between urbanizing forces and those seeking to preserve older neighborhoods’ character.

Advocates for density and walkability say more Denver residents want to live without cars, so no-parking developments could appeal to them, especially near transit and bus lines. No required parking also lowers building costs, potentially allowing for more affordable rents.

“Our idea was to provide a more affordable option for renters that don’t rely on a car to get around,” said Kiely Wilson, a principal at Pando Holdings, in an e-mail about the Humboldt Street project. “We will have brand new apartments with 11.5-foot ceilings for under a $1,000/month. We have spent years studying the product type and making sure we deliver quality spaces and architecture. We intend for this to be a long-term asset for our business.”

But skeptics say not all residents of no-parking buildings will actually forgo cars, simply adding their vehicles to the competition for limited street parking nearby.

Last year’s focus group urged the city to study car-ownership trends and other patterns in denser neighborhoods and to monitor investment in small lots.

The small zone lot parking exemption initially was applied to the East Colfax Avenue corridor starting in 2005, with the intention of providing an incentive to reuse old buildings rather than tearing them down and combining adjacent lots for bigger projects, city planners say.

During the 2010 rezoning of most of the city, the parking exemption was expanded to a range of mixed-use zoning districts for any land use. Most visibly, small lots qualify in areas including 32nd Avenue near Lowell Boulevard in West Highland, on rapidly redeveloping Tennyson Street north of 38th Avenue, parts of South Broadway from downtown to Englewood, the Santa Fe Arts District, Welton Street in Five Points, Cherry Creek North, and parts of Capitol Hill, Uptown, River North and Highland.

According to Kyle Dalton, a principal city planner at the committee meeting, the proposed projects that would qualify for the parking exemption are in various stages of planning review. A few developers are still hammering out conceptual plans that are of a smaller scale; those could change or be withdrawn.

Councilman Paul Kashmann is heading the moratorium proposal in place of Albus Brooks, who is on medical leave. Kashmann told the committee that the small-lot parking exemption initially was intended to apply to development plans for, at most, buildings with a few units.

“This was before the current landscape where we’re seeing large numbers of units (and) micro-housing units of 300 or 350 square feet,” he said. “We’re looking at some developments right now on adjacent lots where we’re getting as many as 100 micro-housing units, with no parking requirements whatsoever.”

The moratorium would not affect a separate parking exemption that applies to any project built downtown, where micro-apartment projects also are underway, some without parking.

As drafted, the moratorium would still allow smaller-scale projects to proceed without off-street parking. The exceptions — still under debate — allow for residential developments with 10 or fewer units, non-residential developments that are no more than two stories or 35 feet tall, and mixed-use projects that meet the first two limitations.

If the council approves the moratorium, the Department of Community Planning and Development says it will create a stakeholder group to recommend permanent restrictions on the small lot parking exemption. It would aim to include a proposed change in a bundle of zoning text amendment changes it’s planning to initiate this fall.