Portland, ME Accessory Structures: ADU Impact Fees (2026)

Portland's municipal code does not include a residential-impact-fee chapter of general application to ADUs. The state statute at 30-A MRS §4364-B(3) caps municipal parking demand for ADUs at the parking required for the principal unit (no extra spaces may be required), and §4364-B(4) exempts one ADU from any density or area calculation — both of which limit the cost levers municipalities may impose on ADU production. Portland's ADU compliance costs accordingly consist of: (i) the standard building-permit fee charged by the Permitting and Inspections Department, typically computed as a fee per $1,000 of declared construction value under the published fee schedule; (ii) separate trade-permit fees for electrical, plumbing, and mechanical work; (iii) water and sewer connection or impact fees charged by the Portland Water District (a separate quasi-municipal entity governed by 35-A MRS) if the ADU requires a new connection rather than tying into the existing principal-unit service; (iv) the Maine state plan-review fee where applicable under MUBEC; and (v) recording fees for the required common-ownership deed restriction at the Cumberland County Registry of Deeds. No school, parks, traffic, or transportation impact fees of general application are imposed on residential ADUs in Portland. Property tax reassessment will occur after construction under 36 MRS §708 (just value reassessment), increasing the lot's annual assessment to reflect the added improvement.