Home additions in Oak Park, IL

Oak Park's zoning ordinance, adopted in 2017, sets minimum single family lot areas from 3,500 square feet in the smallest lot districts to 10,000 square feet in the estate district. Maximum building coverage runs from 35 percent on the largest lots to 60 percent on the smallest, and total impervious surface is capped too. Rear setbacks are 30 or 35 feet, or 20 percent of lot depth, whichever is less, and the height limit in the single family districts is 30 feet.

Your garage counts. Detached accessory structures may cover no more than 20 percent of the lot and are included in the building coverage and impervious limits. A 2018 amendment set garage setbacks at one foot from one side lot line and two and a half feet from the other, and four feet from the rear line where there is rear access.

The village requires drawings for any residential addition to be prepared by an Illinois licensed architect, and a plat of survey showing every structure and setback. Footings go below the 42 inch frost depth in the village's design criteria. Near the north end of Ridgeland Avenue, the old Lake Michigan shoreline, the village may ask for a soils report before it approves a foundation.

Oak Park's code amendments require an NFPA 13D sprinkler system throughout the house when an addition's building area is more than half the existing building area. A plan comparing the two has to go in with the permit. For a modest Oak Park Foursquare that line can arrive sooner than you think, so we size the addition against it early. Separately, the village's all electric rule applies to new residential buildings on a newly created foundation, and its definition covers attached structures, so we raise that with the building division at the start.

In the Frank Lloyd Wright Prairie School of Architecture, Ridgeland Oak Park and Gunderson districts, the village's guidelines say additions should go on the rear or side so the original house stays the main thing seen from the street. Second floor additions should be set back from the front facade, and you cannot raise the whole roof so the attic reads as a new storey.

Dormers are common in Oak Park and have their own rules. A street visible dormer cannot cover more than half of its roof plane, it needs at least one window, and several dormers together must not look like an added floor. If an addition removes historic fabric from a contributing building, that is partial demolition and needs a Certificate of Appropriateness. The commission meets monthly, so we build about thirty days for review into the schedule.