Building an accessory dwelling unit in Newton can cost more than half a million dollars and take nine months just to get through permitting, according to residents and architects who shared their experiences with the Newton Beacon in a report published Monday, Aug. 17.

The city averages about 10 ADU approvals per year since 2014, with more than 120 total units on the ground. Almost 75% are internal conversions, and most detached units are built from historic carriage houses.

Lizbeth Heyer, an Auburndale resident and former chair of the Newton Housing Partnership, has been building a 1,030-square-foot internal ADU since January. The total cost exceeded $500,000. Permitting alone took nine months. Heyer and her husband spent $25,000 more than expected on fire protection, including a sprinkler system and an additional exit.

"It was a very long and convoluted process," Heyer told the Beacon. "My concern is for someone that doesn't do it every day — they might have given up, because it was really complicated and hard."

Heyer's complications stacked up: she needed a zoning variance to convert garage space to residential use, then a special permit because the city measured the unit at 1,030 square feet (including circulation and storage) rather than the architect's sub-1,000-square-foot calculation. She appeared before the city's land use committee. A decades-old clerical error involving a temporary certificate of occupancy added another month while the building commissioner issued a corrective letter.

Patrick Guthrie, a Newton Corner architect who has worked on four ADU projects in the city, said the permitting timeline from initial design to approval runs about six months. He considers finishing a full project in 12 to 18 months "fast." On one carriage-house conversion he worked on, the homeowner faced unexpected costs to hire a civil engineer for utility line installation, expenses that were never flagged during the city's pre-permit inquiry process.

Guthrie said stormwater drainage requirements hit harder on larger ADUs around 1,000 square feet, and that residents are often surprised they need a tree permit even if they don't plan to cut down any trees. Newton's Tree Preservation Ordinance covers all trees with a trunk diameter of six inches or greater.

A second unnamed resident told the Beacon their detached ADU cost more than $600,000, exceeding their budget by $120,000. That included $24,000 for a drainage basin and $20,000 to replace sidewalk sections with granite curbs around a new driveway. The city also required the resident to notify all neighbors in writing before submitting a building permit, causing an additional delay.

City response: Backyard Blueprints contest

Nora Colello, Newton's chief of long-range planning, acknowledged the process can become a confusing back-and-forth between residents, builders and the city, particularly for contractors unfamiliar with Newton's building and zoning laws. That confusion can drive up costs for residents paying architects by the hour.

The city's latest response is Backyard Blueprints, a public ADU design competition funded by a $19,500 AARP Community Challenge Grant that the City Council Finance Committee approved 5-0-1 on Aug. 3, with Councilor Malakie abstaining. Architects, designers and students can submit plans through Oct. 9. Newton residents will vote on the designs in November, and winning plans will become pre-reviewed templates available to homeowners for a flat $1,000 fee paid to the designer. Cash prizes go to the top three: $5,000, $4,000 and $3,000.

When the contest was announced Aug. 11, Colello told the Beacon the goal was to "create tools that make it easier for Newton residents to navigate the permitting process when it comes to ADUs."

Heyer proposed the city hire a "permit ombudsman" at the Inspectional Services Department or the Planning and Development Department to walk residents through the process step by step.

Residents with ADU questions can visit the Inspectional Services Department on the second floor of City Hall or email [email protected]. Design submissions are due Oct. 9.