Prior to World War II and the suburban growth that followed, urban homes were often built with a smaller residence — often tucked from view in the backyard — to accommodate a single relative or a renter.

Yet that dated concept is now a timely topic of debate in Manatee County, where commissioners have indefinitely postponed acting on a proposed “accessory dwelling unit” ordinance because of neighborhood opposition.

The concept may appeal to millennials, young professionals who find market-rate apartments with more space than they may need to be too expensive on their starting salaries.

Middle-aged homeowners may want an apartment on their premises for an elderly parent who can mostly live independently but would benefit from having one of their adult offspring nearby.

Yet, as Manatee commissioners are finding out, homeowner associations and others may raise objections if they think accessory dwellings could add too much density to their neighborhoods and cause parking and other woes.

After some neighborhoods objected, the Manatee County Commission recently tabled for further discussion and possible revisions a proposed ordinance to allow “accessory dwelling units,” such as garage apartments, on lots designated for single-family homes. Several other jurisdictions in the Tampa Bay area already allow ADUs in designated residential zones. Proponents of the idea say it could create more affordable housing. Opponents say it could alter the density, character and parking availability of long-established subdivisions.

The cities of Sarasota, Bradenton, St. Petersburg and Tampa allow accessory dwellings in specified areas.

Sarasota County’s code does as well, though its planners are working on revisions pertaining to density calculations in that ordinance for which public hearings will be conducted in August and September.

Venice does not allow accessory dwellings in its “traditional residential districts,” Jeff Shrum, the city’s development services director, said. The city is in the process of updating its land development code by early 2020. “This will be a topic of conversation during the discussion of zoning districts and alternative housing identified in the city’s comprehensive plan,” Shrum said. He expects “any increase or potential increase in densities is likely to be met with a significant amount of opposition, no matter the rationale.”