On Nov. 19, the Zoning Board of Appeal rejected a non-profit group's plans to convert a Shawmut Avenue office building into affordable apartments because it would have one apartment on the first floor despite being in Boston's coastal flood resilience overlay district, where residences are supposed to be higher than that in anticipation of flooding as sea levels continue to rise and storms become more fierce.

The board's vote, however, will likely only delay, not stop, Inquilinos Boricuas en Acción's proposal to convert space inside 403-405 Shawmut Ave. into six apartments, all to be rented at affordable rates.

The board denied the proposal "without prejudice," which means the non-profit can come back in less than a year with a new proposal, for example, one in which the building only has five residential units, on the upper floors, or it somehow rejiggers its plans to fit six units above the ground level and its anticipated possible flood level in the coming decades.

"This is coming as a bit of a surprise," IBA attorney Jacob Taylor said.

The overlay district, adopted in 2019, covers parts of the city from East Boston to Dorchester that could experience significant ocean, or in some cases, river, flooding in the future.

The IBA proposal was part of a larger package reviewed by the zoning board, in which IBA also sought approval to do extensive renovations on several buildings in the South End in which it already rents affordable units, from roof replacements to kitchen and electrical upgrades.

Those projects, along with the Shawmut Avenue proposal, needed separate zoning-board approval because they sit in another "overlay district" in which new buildings or large renovation projects have to be certified as not affecting the amount of rainwater that percolates into the ground. That water is necessary to keep the wooden pilings that support so many buildings in the South End, the Back Bay and Bay Village from drying out, which could lead to rotting.

The board approved all of the projects, including the Shawmut Avenue one, as compliant with the city's groundwater-conservation regulations.