Twenty-eight Broadway houses went dark Saturday as striking stagehands picketed in front of theaters, and disappointed consumers found their Rialto plans abruptly scuttled.

Strike was called Friday night by IATSE prexy Thomas C. Short, allowing little time to warn ticketbuyers.

Initial show affected Saturday was “Dr. Seuss’s How the Grinch Stole Christmas,” which was to have had the first of four performances at 11 a.m. News crews shot footage of disappointed theatergoers as production teams handed out fliers assuring patrons their tickets would be refunded.

Box offices were shuttered as their unionized employees honored the stagehands’ picket lines. Actors’ Equity endorsed the strike, while instructing its members to show up and sign in for work as required by that org’s contract.

Members of the stagehands’ union, Local One, carried signs and handed out an explanatory statement to passersby that highlighted the boom in Broadway grosses in recent years.

The union and the trade association of Broadway producers, the League of American Theaters and Producers, held dueling press conferences over the weekend to lay out their cases.

League prexy Charlotte St. Martin, at the Saturday afternoon conference called by producers, reiterated the risk to Broadway productions, saying that despite heightened grosses, only one in five productions recoups. She also repeated the League’s aim for a new agreement with the union that would reduce contractual obligations that producers consider outdated and overly costly featherbedding.

The League estimated that a strike costs the New York City economy $17 million a day, a tally combining box office losses with the ripple effects on surrounding local businesses that depend on theatergoer traffic.

At the union’s press conference Sunday, Local One prexy James J. Claffey said that maintaining standards of safety and efficiency was paramount, as was fighting to protect members’ incomes that might be significantly lowered by the new work rules supported by the League.

Neither side offered an estimation of how long the strike might last.

“As long as it takes,” said Michael David, producer of “Jersey Boys” and “The Farnsworth Invention.”

Over the past few years, the League has accumulated a war chest said to have reached $20 million in funds, which would help sustain productions during a work stoppage. The union, meanwhile, has its own reserve of around $4 million plus additional coin to support members of other unions affected by a strike.

The Gotham mayor’s office has previously offered to aid the two orgs in reaching a deal, but Local One declined the offer. On Saturday, Mayor Michael Bloomberg released a statement that encouraged a resolution, saying, “While this is a private labor matter, the economic impact is very public and will be felt far beyond the theaters closed today.”

An extended Broadway shutdown poses particular risks for productions with low advance sales as well as shows scheduled for limited engagements, which have only a short time to recoup capitalization costs.

“The economics of it are very fragile,” said James Sanna of Running Subway, the producing org behind the seasonal run of “Grinch.” “Something like this is devastating to us.”

Meanwhile, the eight productions unaffected by the strike — which are in theaters that have separate agreements with the union — anticipated picking up biz from aud spillover. Off Broadway productions also looked likely to get a boost.

Rialto shows unaffected by the strike include nonprofit productions “Mauritius,” “The Ritz,” “Pygmalion” and “Cymbeline,” as well as commercial shows “Young Frankenstein,” “Mary Poppins,” “Xanadu” and “The 25th Annual Putnam County Spelling Bee.”

Local One and the League have been wrangling over a new agreement for several weeks.

Stagehands have been working without a contract since their previous agreement with producers expired in July.

Talks broke off Oct. 9, and producers have been implementing some of their proposed work rules without union consent since Oct. 22.

Negotiations picked up again Nov. 7, in sessions attended by Intl. Alliance of Theatrical Stage Employees prexy Short. After a second day of talks was said to be unproductive, Short granted Local One strike authorization Nov. 8.

At issue are contractual employment obligations, particularly the hiring requirements for the process of loading a production into a Broadway theater. Producers seek to establish flexibility in those requirements, while stagehands refuse to give up what they see as hard-earned protections of their livelihood without receiving other benefits in exchange.

Over the weekend, ticketbuyers expressed some frustration — such as a tearful girl clutching her mother in front of “Mamma Mia!” — but in general, most were merely resigned.

“We were, like, counting down the days,” said a teenager from Long Island who came in early Saturday to line up for “Spring Awakening.” “I’ll come back, but this morning I was so furious.”

“I’m not a union person, but they have the right to do what they want,” said an older woman from Alabama, who had tickets to see “Wicked” Saturday afternoon and “Cyrano de Bergerac” that night. “That’s America for you.”

One family had come in to the city from Hershey, Pa., to catch the Saturday matinee of “Wicked,” having purchased tickets three months ago. “There were a few tears,” the mother admitted.

But soon thereafter, the family headed off to nearby New World Stages, to see if they could score matinee tickets to Off Broadway tuner “Altar Boyz.”