City officials are hoping that waivers on fees and charges will encourage more homeowners to consider joining the fledgling Accessory Dwelling Unit program.

Mayor Kirk Caldwell on Thursday signed Bill 27, which is expected to save anyone applying for an ADU permit over a two-year period as much as $10,000 by waiving all building permit, grading permit and inspection fees as well as wastewater facility charges. It also removes a park dedication fee for ADU permit applicants.

The Honolulu City Council passed the bill, which was drafted by the Department of Planning and Permitting, on July 6.

The ADU program is designed to make it easier for individual homeowners to carve out or build rentable living spaces, or second dwellings — not just for relatives, as has been allowed in limited numbers previously through “ohana” permits, but for nonrelatives as well.

An ADU can be attached or detached from the original home. It must have a separate kitchen, bedroom, bathroom and a dedicated parking stall.

Caldwell said Thursday that approximately 121,000 lots on Oahu might be eligible for a second unit of between 400 and 800 feet, as allowed by the ADU law approved last year to address “a demand that’s unmet.”

Bill 27 was triggered by complaints and the slow response to the rollout of the ADU program. Architects, planners and builders told city officials that while building an ADU might not be that expensive, “when you start looking at the different fees the city charges — sewer hookup fees, permitting fees, grading fees, grubbing fees — it can total to $7,000 to $10,000,” Caldwell said.

A flat-rate sewer hookup fee alone costs $6,634, city officials said.

To date, the Department of Planning and Permitting has approved 39 ADU permits, while 129 are “in the process,” Caldwell said. The funding breaks allowed by the law would be applied retroactively to those homeowners through refunds, he said.

Breaks will not, however, be given to homeowners seeking an after-the-fact building permit to convert an illegally constructed structure into an ADU, city officials said.

In approving the new bill, the Council added a provision requiring that permits must be acted upon within 60 days of an application’s submission. To facilitate that, the DPP is requiring that applicants fill out a “pre-check” form.

DPP Director George Atta said the city issued 778 pre-check applications, most of them this year. Many have been waiting for the waivers bill to be approved, he said.

Among the applicants was Greg Thielen, owner of Complete Construction Fees Hawaii, who wants to convert the recreation room in his Kailua home into an ADU. Atta said it was Thielen’s letter of complaint about the fees that helped prompt the second bill.

“The waiving of fees removes a substantial barrier for homeowners considering the construction of an ADU on their property,” Thielen said during a news conference at the Frank Fasi Municipal Building permitting center.

Atta said at least a half-dozen homebuilders and contractors of packaged homes are seeking pre-approvals of their models that would cut down on the cost and time for putting in place ADUs.

Travis Wittmeyer, owner of Blue and Green Innovations, said that 75 to 80 homeowners have approached his company about building ADUs. The company has pre-engineered plans that it will make available for free to a homeowner seeking an ADU.

The semiautonomous Honolulu Board of Water Supply is considering a plan to allow breaks for water hookup fees, which average about $5,000, Atta said.

The ADU program is among several initiatives rolled out by Caldwell in September 2014 to tackle the affordable-housing crunch. Another initiative, which requires developers to set aside more affordable units that are within reach of those in lower-income strata, is still being worked on, Caldwell said.

More information about ADUs is available online at honoluludpp.org.