ADU rules in McHenry County, IL — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
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.
Under UDO § 16.56.030O, ancillary dwelling units are subject to the Zoning District Uses table and may be attached to or detached from the principal home. They must meet all building code and McHenry County Department of Health well/septic requirements. Only one ADU is permitted per lot, it must be owner-occupied (owner may live in either unit), and one extra parking space is required. A detached ADU may be no more than 35 feet tall, cannot sit in the effective street yard, must meet principal-structure side and rear setbacks, and its footprint cannot exceed 900 square feet. This governs unincorporated land; cities like Crystal Lake, Woodstock, and McHenry set their own rules.
Zoning enforcement by the county Zoning Enforcement Officer; nonconforming or unpermitted ADUs must be brought into compliance or removed, and variations are required to legalize noncompliant units.
Other ordinances people look up for this city. Green dot = verified primary-source excerpt.
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Crystal Lake collects yard waste and food-scrap compost weekly at the curb from April 1 through November 30. Leaves and grass must go in biodegradable paper ...
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Crystal Lake uses a color-coded water-conservation system. During a declared 'Yellow' condition, odd-numbered addresses water on odd dates and even addresses...
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Crystal Lake Chapter 526 lists noxious weeds - burdock, ragweed, thistle, poison ivy, wild mustard and others - plus any unmanaged vegetation as nuisance gre...
See how McHenry County's adu rules rules stack up against other locations.
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