5 rules for unincorporated McHenry County, Illinois.
Verified from official government sources
The McHenry County UDO allows one ancillary dwelling unit (ADU) per lot in unincorporated areas. It can be attached or detached, must not exceed the principal home, is capped at two bedrooms, and the lot must be owner-occupied.
McHenry County UDO § 16.56.030O.3.b–c
Ancillary dwelling units shall be limited to no more than 2 bedrooms. Ancillary dwelling units shall not exceed the size and scope of the principal residence.
In unincorporated McHenry County, a shed and other accessory structures must sit at least 10 feet from any lot line. In R-1, R-2 and R-3 residential districts, detached accessory structures are capped at 14 feet (flat roof) or 18 feet (pitched roof).
McHenry County UDO § 16.56.050A.1.d
Accessory structures shall be located a minimum of ten (10) feet from any lot line, unless otherwise specified by this Ordinance.
In unincorporated McHenry County you cannot convert a detached garage or other accessory structure into living quarters unless it qualifies as a permitted ancillary dwelling unit under the UDO. Otherwise, an accessory structure may not be used as a dwelling.
McHenry County UDO § 16.56.050A.1.a
No accessory structure may be used as a dwelling unit, unless permitted as an ancillary dwelling unit in accordance with § 16.56.030O.
A carport is an accessory structure under the McHenry County UDO. In R-1, R-2 and R-3 residential districts detached accessory structures are limited to 14 feet (flat/mansard roof) or 18 feet (pitched roof) tall, and must sit at least 10 feet from any lot line.
McHenry County UDO § 16.56.050A.2.a(2)
In the R-1, R-2, and R-3 Districts, detached accessory structures are limited to fourteen (14) feet in height for a flat or mansard roof design, and eighteen (18) feet in height for a pitched roof design.
McHenry County has no separate tiny-home category. A tiny home can only be a legal second dwelling if it qualifies as an ancillary dwelling unit under the UDO. Mobile home trailers and recreational vehicles are expressly barred from serving as an ADU.
McHenry County UDO § 16.56.030O.4.e
Mobile home trailers and recreational vehicles are prohibited from being used as an ancillary dwelling unit.
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