One of Broadway’s prime musical houses, the St. James Theater, will soon begin an expansion of its stage that will push the back wall of the theater out into the alley behind it. Work begins this summer, just as the Helen Hayes Theater next door begins its own renovations — and as the St. James’ current tenant, “Something Rotten!,” continues its performances unabated.

The alley between the St. James and the Helen Hayes, two theaters that stand side by side on West 44th Street, has previously been part and parcel of the Hayes. But as Second Stage undertook its purchase of the Hayes, Jujamcyn Theaters, the owner of the St. James, bought the alley from the nonprofit. The goal is to deepen the St. James stage by ten feet, in order to accommodate the hefty technical demands of many of today’s splashy musicals. (Both Jujamcyn and Second Stage are keeping mum on the cost of the puchase.)

“At the end of it all, the Hayes will be a beautifully renovated play house and the James, which is already a premier musical house, will have a stage that can accommodate anything our creative teams dream up,” said Jujamcyn president Jordan Roth.

No one’s saying it out loud, but the St. James already has its first large-scale musical lined up for the newly expanded space — and it’s a doozy. Disney Theatrical’s stage adaptation of “Frozen” is poised to claim the venue when it skates onto Broadway in spring 2018. But none of the players involved will cop to that on the record, since “Frozen,” which premieres in Denver in summer 2017, hasn’t announced its New York specifics yet, and “Something Rotten!” is still chugging along in an open-ended run with no closing date announced. (The stage expansion, it’s said, had been planned for several years, predating “Frozen.”)

While “Rotten” is still running, Jujamcyn will begin the construction and renovation in the alley that will prep the space to become a part of the St. James stage, in a process that will include clearing out a few floors of offices that occupy the upper reaches of the alley. Sometime in 2017, the theater’s current back wall will be knocked out to connect the stage with its new expansion.

The process gets underway as Broadway real estate has become a topic of concern for commercial producers. The scarcity of available Broadway theaters has become a common state of affairs in recent years, but now the Hayes is about to begin its lifespan as a nonprofit house, the St. James seems to  be spoken for, and the Palace Theater is due to undergo a complicated elevation process that will take that venue out of commission for three years or so. There are also rumors that the construction of a proposed new Broadway theater, being built by the Shubert Organization next to the Imperial Theater, would at some point darken the Imperial Theater next door — but the Shuberts have never publicly confirmed whether that theater is in fact in the works, much less what kind of impact its construction would have.

The current tenant at the Palace, “An American in Paris,” just announced it will close in January, but it’s not yet certain whether the renovation on that theater will begin immediately after the production exits. Meanwhile, Jujamcyn will begin its work on the 44th Street alley later this summer, while Second Stage will start its own renovation process on the Hayes at around the same time.