Boston Mayor Michelle Wu is revamping the city’s requirements for commercial developers to support daycare and early childhood programs.

The executive order clarifies the requirements for on-site day care facilities and a fee to support off-site programs for new commercial developments in 14 zoning districts in and around downtown Boston. Affordable day care is increasingly out of reach for working families, Wu said.

“Every worker in Boston should have access to the types of support that this program and place represents,” Wu said during a press conference at Boston City Hall’s childcare center, created in 1989 by former Mayor Raymond Flynn.

New commercial buildings are required to set aside space for day care centers on-site or pay a cash-out fee to support existing or new programs off-site, which would average $400,000 for a typical new building. The program will generate an estimated $800,000 to $1 million a year based upon the current pace of development, Wu said.

The funding could be used to bolster staffing at child care programs that have insufficient staff, Wu said.

In the Leather District, for example, new buildings with 100,000 to 200,000 square feet are required to include set aside 2 percent of their gross floor area for day care. The requirement expands on a sliding scale to a minimum 12,000 square feet for projects that are at least 1 million square feet.

A Boston Planning & Development Agency official said existing regulations will be updated to provide clear and transparent guidance to developers on what’s required.

“This is a theme that applies to many of our development requirements in Boston,” said Devin Quirk, the BPDA’s deputy chief of development and transformation.

The executive order clarifies the existing zoning language and places the Boston Office of Early Childhood in charge of how the off-site fees are distributed.