1 county-level rule, plus city-specific rules for 2 cities in Hillsborough County, New Hampshire.
Verified from official government sources
Hillsborough County itself does not regulate Accessory Dwelling Units. Under New Hampshire's Home Rule structure (RSA Title LXIV), zoning and ADU regulation is handled by the individual cities and towns - Manchester, Nashua, Merrimack, Hudson, Milford, etc. New Hampshire's statewide ADU enabling law at RSA 674:71-73 requires every municipality with single-family zoning to permit at least one ADU per single-family lot as a matter of right.
2 cities in Hillsborough County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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Hillsborough County Ordinance Hub →