A Tribeca glass office building being redeveloped over a Verizon substation for the glamorous Spring Studios is being flipped to an entity of American Realty Capital Properties (ARCP) by Joseph Sitt, The Post has learned.

In April, Sitt agreed to buy the 90-percent completed Morris Adjmi-designed project at 50 Varick St. for $83 million from Estate4, a Milan-based developer, sources said. Sitt has now agreed to sell the contract to buy the building, a 100,000-square-foot multi-story commercial condominium, to the publicly traded ARCP for $90 million.

The building, by the Holland Tunnel entrance, has views to the Hudson River. London-based Spring — akin to Milk Studios — will also have use of a large roof deck.

According to public documents, condo by-laws require the building to be entirely smoke-free, which may become an issue at some point for some of Spring’s fashionista clients.

No one responded to requests for comment.