The state’s new housing law aimed to help fix the affordability crisis. Experts now say it won’t deliver.

And towns like Norwood are the reason why.

Its new zoning rules looked transformational on paper — so much so that one Norwood Select Board member suggested it would forever alter the character of the town — but they were actually crafted to do close to as little as possible without violating the new law.

Indeed, the plan calls for more than 2,000 new homes in a suburb of about 30,000 people. In practice, it could create more like 300.

Norwood is no outlier. As towns around Greater Boston vote on their MBTA Communities plans — most of which are due by year’s end — a Globe review of dozens of preliminary and already-passed zoning strategies found that towns are deliberately designing plans that cleverly end-run the new state mandate.

Some towns are simply zoning to allow apartment buildings in places where apartment buildings already exist. What developer will find it economically wise to tear down an existing building to create a new one of similar size? Others are writing their zoning rules in good faith, but capping building heights and densities in ways that effectively make new development impractical. All these steps are designed to limit new building to a scale local community government can swallow or to prevent it altogether.

The result, according to developers, zoning experts, and an analysis of historic development patterns here, is that MBTA Communities will more likely generate somewhere between 20,000 and 40,000 new units over the next two decades. Even that might be an overestimate.

“Some communities have figured out that if they don’t want to produce housing, it’s not that difficult to cut MBTA Communities off at the knees,” said Jay Doherty, CEO of developer Cabot Cabot and Forbes. “I won’t say the law is not helpful. Anything’s helpful. We need housing. But I’m afraid the way communities are treating it right now will mean that it just won’t be enough to move the needle.”

The law’s Achilles’ heel, some advocates say, is how much discretion it gives communities over where to put the new zoning it mandates.

That particular wrinkle is a nod to the state’s long tradition of local control over land use, but in practice, it allows towns to comply by zoning for new apartment buildings in places where they know nothing new is likely to be built. Or maybe they permit another floor or two above what’s already there, but tearing down a three-story apartment building to build a four-story version makes little economic sense.

The result? Zoning plans that sound far more ambitious than they will actually be. And that has some worried that, after so much local drama, MBTA Communities won’t make a meaningful dent in a housing shortage that is an increasingly urgent threat to the regional economy and the people who live here.

“The average suburban voter who thinks this is a huge deal might believe this is all we need to do, or their town needs to do, to solve the housing crisis,” said Luc Schuster, executive director of The Boston Foundation’s research center Boston Indicators. “My concern is that people will become skeptical about zoning reform when this doesn’t solve the problem.”

An example of how towns are minimizing the law’s impact played out in Norwood earlier this year, where planners chose three different areas to rezone, each clustered around one of the town’s three commuter rail stops.

The first is a clutch of older, commercial and industrial lots across from the Norwood Central station, a spot that most in town agree is prime for new development. The other places Norwood rezoned? Quite the opposite. Roughly two-thirds of the land in Norwood’s plan is already covered by housing developments. That, say the people who wrote the plan, was quite intentional.

“We’ve strategically placed these districts in areas that have multifamily housing,” Norwood planner Sarah Dixon told the town’s Select Board earlier this year. “The market incentive to tear down [an apartment complex] and rebuild isn’t there.”

Yet it meets the letter of the law. Based on the town’s population and level of transit access, MBTA Communities requires Norwood to draw zoning that could enable 2,045 new units. So that’s what Norwood did. If developers bought and razed all the existing buildings in the zones and built new ones at the maximum allowable height and density the new plan allows, they would have room for 2,045 apartments and condos.

But most of those existing buildings aren’t going anywhere. There are already about 1,300 apartments in the areas Norwood rezoned. Save for those few low-slung auto shops and other commercial properties ripe for redevelopment, there’s little incentive for a developer to do much of anything.

In effect, the law lets towns draw districts in places they know will never be developed. And towns are taking full advantage.

In Chelmsford, for example, the Planning Board is rezoning an already built-out stretch of Route 110. It contains no vacant or industrial parcels, just condo complexes. Planning Board member Annita Tanini described the board’s strategy as making “as many barriers [to development] as possible.”

Wellesley is revamping the zoning where The Nines, an 850-unit apartment complex on the town’s border with Newton, now sits. On paper that fulfills some 60 percent of the new law’s local mandate. Dedham did something similar when it passed its plan last year, zoning over several existing and permitted apartment buildings and Legacy Place, a thriving mixed-use complex. One developer who requested anonymity to discuss a town their firm does business in reviewed Dedham’s zoning said they “would be shocked to see one unit of housing created.”

An even more extreme example is Sudbury, where local officials drew two zoning districts roughly five miles apart, each atop sprawling apartment complexes.

“This is the sort of thing we’ve come to expect with statewide zoning mandates,” said Jenny Schuetz, a zoning researcher with the Brookings Institution. “The Boston suburbs have spent decades doing everything they can to prevent new housing development. I suspect that MBTA Communities is going to be the same.”

The Executive Office of Housing and Livable Communities, the state housing office responsible for reviewing MBTA Communities plans, only considers whether zoning will be economically feasible in certain instances, specifically when communities want to require a portion of new housing to be income-restricted at lower rents. In other words, in places like Norwood or Chelmsford, whether or not any housing would actually be built as a result of their zoning won’t be relevant for state approval.

In a statement, a spokesperson for the state housing office said the agency is committed to ensuring communities pass compliant zoning.

“Massachusetts must plan for more housing,” the agency said in a statement. “EOHLC will continue to ... help communities develop districts that meet the urgency of the moment.”

Of course, even town officials who support MBTA Communities face delicate politics. Resistance to the law has grown as more communities write their plans. Opponents have tended to be louder, warning of thousands of new residents they say no town can support. At the same time, the law is the law, and state housing officials and Attorney General Andrea Campbell have been clear they’ll sanction communities that don’t comply. Campbell has already sued the town of Milton for failing to meet the law’s requirements, and the Healey administration limited the town’s access to certain grant programs.

Dixon, the Norwood planner, said her town had to walk a fine line. Local leaders didn’t want to pass a plan that was only compliant on paper, but they also needed to come up with something that could get approved by Town Meeting. She acknowledges the zoning will result in only maybe three or four new buildings in the next few years.

“It’s not the most ambitious plan,” she said. “I don’t know that we would have been successful if we proposed something more aggressive than this.”

To be sure, some communities are embracing the law and the idea that they need to grow. Some 50 cities and towns have already passed plans and some early adopters, like Arlington and Lexington, went well beyond what’s required.

Even those good-faith plans, though, may have a limited impact.

Take Arlington. After a debate so fierce the police had to be called to one meeting, the town last year passed a plan that rezones key stretches of two major commercial arteries, Massachusetts Avenue and Broadway, and makes room — on paper — for more than 3,200 homes, far exceeding the 2,046 the law requires of Arlington.

But here, too, it’s not that simple. Mass. Ave. and Broadway are already lined with two- and three-story residential buildings, and Arlington’s zoning plan mostly limits new structures to four stories. What’s more, many of the lots are themselves pretty small, meaning a developer would have to acquire a bunch of them, one by one, to build anything substantial. That adds time and cost.

What’s left are parcels only big enough for small and midsize projects, the sort of developments that are challenging for builders to finance because they have to be able to make a profit on relatively few units. The result is a mismatch between the kind of development that towns want or are willing to see, and the kind of project developers can make work financially.

Doherty, of Cabot Cabot and Forbes, said these days he generally needs five stories of height to make a project work. Margins have gotten tighter as interest rates and construction costs have soared, and when he looks around at the zoning plans towns are adopting, he sees very few parcels that could support the scale of projects he builds.

Sandi Silk, senior vice president at Jefferson Apartment Group, a national developer that has built thousands of apartments in Greater Boston, has looked for sites in many communities and come to a similar conclusion: The zoning many communities have passed just isn’t going to work for many projects, particularly bigger ones.

“What this law has turned out to be is communities enabling the permitting of small scale multifamily projects,” Silk said. “But we’re not going to solve the housing crisis on the backs of [that].”

Indeed, Arlington’s plan theoretically makes room for more than 3,000 new units, but in reality planners there say they’ll be lucky to see 200 built over the next decade. Newton and Lexington adopted similar strategies, and the build out will likely be far less than some projected as well.

As Schuster, of Boston Indicators, sees it, MBTA Communities has been oversold by both housing advocates and opponents.

“MBTA Communities is a good law, and it is certainly better than nothing,” said Schuster. “But we’ve spent too much time focusing on a law that is not the be-all end-all solution. We have to start talking about what we can do next.”

Andrew Brinker can be reached at andrew.brinker@globe.com. Follow him @andrewnbrinker.