Site plans in Illinois

Five conditions that shape an Illinois site plan

Illinois does not approve private site plans at state level. Approval is municipal or county, and state and regional agencies attach their own permits for highway access, stormwater discharge, floodways, sewer connections and tanks. The IDFPR Code Enforcement Manual tells code officials that before a permit issues, special permits may be needed from historic preservation authorities, US or Illinois EPA, US or Illinois DOT, the Army Corps of Engineers, IDNR, the Coast Guard or the FAA, and that the owner or design professional must find out which apply ^[1]. Five conditions decide how an Illinois plan is drawn and how long it takes.

1. The site plan carries a surveyor's seal when it carries the boundary. The Code Enforcement Manual states that if a site plan shows "any technical information, such as dimensions or bearings, relating to boundaries," it must be signed and sealed by a professional land surveyor as well as by the design professional responsible for the proposed conditions, and that this includes a boundary survey used as an underlay ^[1]. Nearly every commercial plan is drawn over a survey, so the permit-set site plan in Illinois is a two-seal sheet.

2. Population decides what a town may demand. Under Article VII, Section 6 of the 1970 Constitution, a municipality over 25,000 is a home rule unit automatically, and a smaller one becomes home rule by referendum ^[6]. A home rule unit may act without a statutory grant; a non-home rule municipality may act only where the Illinois Municipal Code (65 ILCS 5) grants the power ^[7]. Separately, a municipality's subdivision and comprehensive plan jurisdiction reaches unincorporated land within 1.5 miles of its corporate boundaries, unless another municipality already holds it ^[8]. A county parcel can need a village's plat approval even though the village has no zoning power over it, and home rule does not widen that reach ^[7].

3. Stormwater has a different owner on each side of a line. In Chicago, the Stormwater Management Ordinance (Chapter 11-18) governs development that disturbs 15,000 or more square feet or creates 7,500 or more square feet of at-grade impervious surface, and stormwater approval must be in hand before a building or sewer permit can issue ^[9]. In suburban Cook County, the Metropolitan Water Reclamation District (MWRD) is the stormwater authority under its Watershed Management Ordinance, with a permit triggered by disturbance of more than 0.5 acre ^[3]. DuPage, Kane, Lake, McHenry and Will hold countywide stormwater authority under 55 ILCS 5/5-1062 ^[10]. Even the rainfall data differs: the IDNR model ordinance references Illinois State Water Survey Bulletin 70, and MWRD requires Bulletin 75 ^{[11, 3]}.

4. The state highway is usually the critical path. IDOT advises allowing 9 to 14 months from first submission to permit issuance for larger developments, subdivisions or permits with signals or turn lanes ^[2]. On a commercial site that takes access from a state route with a new signal or turn lane, the access permit sets the schedule, not the zoning hearing.

5. No part of the state is code-free. Public Act 103-0510 created the State Building and Residential Codes Act, effective 1 January 2025 ^[5]. Where a county or municipality has no building code, construction must still meet the Capital Development Board baseline, which includes the IBC with Appendix G (flood-resistant construction), and a qualified inspector must state that the building complies ^[12]. Every Illinois site plan is drawn against a code; the question is only who enforces it.

Approval layers: state, region, county and municipality

Local review runs on one of two tracks. By-right projects that meet every zoning standard go through staff review in a community development or building department, often with an internal committee drawing in engineering, fire and public works; that track is measured in weeks. Planned unit developments, special uses, variations, rezonings and annexations go to a Plan Commission recommendation and then a decision by the corporate authorities after a noticed public hearing; that track is measured in months.

Outside municipal fire departments, Illinois fire service is often delivered by independent fire protection districts, which are separate units of local government with their own review and fees. On rural and unincorporated commercial sites, district review commonly turns on turning radii, access width, hydrant spacing and fire lane geometry, so the district belongs on the first-week call list.

Land division runs under the Illinois Plat Act, 765 ILCS 205, whose exemptions decide whether a plat of subdivision is needed at all ^[17]. Only the professional land surveyor who signs a plat, or a person with that surveyor's written authorization, may record it ^[1].

Who prepares and seals what

Illinois licenses four design professions separately, each under its own Act: architects (225 ILCS 305), professional engineers (225 ILCS 325), structural engineers (225 ILCS 340) and professional land surveyors (225 ILCS 330), all regulated by IDFPR ^[1]. The Code Enforcement Manual draws the lines a permit set has to follow:

The seal goes on the first sheet of any bound set and on every loose sheet. It must be reproducible (embossed seals do not satisfy the Acts), it may be applied electronically, and it carries the current date and the license expiration date. The cover sheet lists the project, the design firm and its Professional Design Firm registration number, every code used, a drawing index and which drawings each seal covers. Only Illinois licensees may seal Illinois work ^[1].

The retaining wall rule matters on almost any site with grade change, a loading dock or a detention basin: the wall detail belongs to a structural engineer, not to the civil engineer drawing the grading around it ^[1].

A preliminary site plan from the studio is the layout those seals sit on. It fixes site disposition, buildings, drive aisles, parking, pads and yield, with a site data table carrying acreage, zoning, setbacks and parking required against provided. Developers take it to early conversations with a municipality, to a lender and to a contractor for pricing; the client's Illinois engineer of record, structural engineer and surveyor then build the sealed permit set on it. The guide to who prepares a site plan sets out that division of work, and preliminary vs final site plan shows where the sheet changes hands. For an Illinois project that needs coordination across those disciplines, see the site plan consultant and site plan architect pages.

Statewide overlays

The building code baseline since 2025

From 1 January 2025, a local code must regulate the structural design of new non-residential buildings at least as stringently as the IBC, rehabilitation at least as stringently as the IEBC and residential structure at least as stringently as the IRC ^{[5, 12]}. In a jurisdiction with no code, a commercial building must meet the IEBC and IBC (1/1/25 edition, including Appendix G, excluding Chapters 11, 13 and 29), the NEC, the Illinois Energy Conservation Code, the Illinois Accessibility Code, the Illinois Plumbing Code and the Fire Prevention and Safety Rules including NFPA 101 ^[12].

Three timing rules follow. A municipality or county adopting or amending a code must notify CDB at least 30 days before the effective date. Once a permit issues, the code in effect on 1 January of the calendar year in which the permit was applied for governs for the life of the permit. From 1 January 2027, building inspectors must hold ICC certification ^[18]. Because the baseline allows the current edition or the most recent preceding one, two adjacent jurisdictions can reference different ASCE 7 editions and so different design loads ^[12]. CDB's directory of locally adopted codes is the first check for any project outside a major city ^[19].

Energy and accessibility

The Illinois Energy Conservation Code (20 ILCS 3125/15) applies statewide; the current edition is the 2024 IECC as amended, effective 30 November 2025 ^[20]. The Illinois Stretch Energy Code is mandatory for projects authorized or funded by CDB and optional for municipalities that adopt it ^[21].

The Illinois Accessibility Code (71 Ill. Adm. Code 400), adopted under the Environmental Barriers Act (410 ILCS 25), has the force of a building code ^[13]. It is a minimum that binds every governmental unit, home rule units included, and any of them may go stricter; where a permit is required for a public facility, a Statement of Compliance is part of the permit process ^[22]. Its defined accessible route expressly includes exterior routes: parking access aisles, curb ramps, crosswalks at vehicular ways, walks, ramps and lifts ^[23]. Accessible parking counts, access aisle geometry and the route from parking to the entrance are therefore set by a state code layered over the federal ADA, and a plan must satisfy both. The studio's note on ADA compliance in commercial site plans covers the federal side.

Construction stormwater: ILR10

County stormwater outside Cook

The five collar counties (DuPage, Kane, Lake, McHenry and Will) received countywide stormwater powers under Public Acts 85-905 and 85-1266, codified at 55 ILCS 5/5-1062; each has a stormwater management planning committee with equal county board and municipal representation ^[10]. DuPage's ordinance, effective February 1992, supersedes less restrictive municipal rules, and where county and other rules differ the most restrictive controls ^[25]. In McHenry County, 21 of 30 municipalities are Certified Communities that enforce the county's Stormwater Management Ordinance within their limits ^[26]. The studio's note on stormwater as a site plan variable covers how detention and retention rules change a layout.

Floodways, wetlands and species

IDNR's Office of Water Resources permits construction in regulatory floodways under 615 ILCS 5/18g ^[15]. In Cook County, MWRD regulates isolated wetlands only and expressly leaves Corps-jurisdictional wetlands to the US Army Corps of Engineers under Section 404 ^[3]. Statewide, IBC Appendix G brings flood-resistant construction standards even to jurisdictions without a building department ^[12].

Underground storage tanks

The Office of the State Fire Marshal issues permits to install, repair, upgrade, close or remove a tank, and handles registration, contractor certification and UST Fund eligibility. A release is reported to the Illinois Emergency Management Agency; corrective action then runs through the IEPA Leaking UST Section, which issues the No Further Remediation letter ^{[27, 28, 16]}. The NFR letter must be filed with the county recorder within 45 days so that engineered barriers and institutional controls run with the land, and those controls limit where a new plan can excavate, plant or route utilities ^[27]. The UST Fund pays a maximum of $1,500,000 per occurrence, less a deductible of $5,000 to $100,000 set by OSFM ^[28].

State highway access

Work in the right of way of an Interstate, US route, Illinois route or other state-maintained road needs a permit under 605 ILCS 5/9-113, and access driveway standards sit at 92 Ill. Adm. Code 550. Applications go to the IDOT District office, not a central office, and requirements vary by District. The submittal is a letter of request with a description of work, location map, detailed drawings, traffic studies and a traffic control plan, and a bond is commonly required ^[2]. District access guidelines set the geometry that drives the plan: District 2's, for example, set intersection sight distance by design speed and crossing width, and clear storage distance near rail crossings ^[29].

Top jurisdictions

Chicago

Chicago runs its own zoning, building and stormwater codes; the Chicago site plan page covers the city in depth. Chapter 17-13 of the Zoning Ordinance holds the review procedures, including Site Plan Review at 17-13-0800, and Chapter 17-8 sets Planned Development thresholds, mandatory at 17-8-0500 and elective at 17-8-0600 ^{[30, 33]}. A site plan review submittal includes a map of surrounding land uses and buildings for one block in all directions, elevations of every proposed facade and the specified materials; projects proposing alternative compliance with on-site open space standards also go through it ^[31].

Planned Developments run in two parts: Part I review (zoning plus Planning and Design Review by DPD, leading to the PD ordinance) and Part II review of construction plans for conformance with the approved PD ^{[34, 35]}. Later phases of a PD go through site plan review under 17-13-0800, review fees are paid in installments, and for some PDs site plan approval requires a courtesy presentation to the Chicago Plan Commission at a public meeting ^[36].

The building code is Title 14B, based on the 2018 IBC, applying to most permit applications started on or after 1 August 2020; the accessibility provisions of Chapter 14B-11 and Section 14R-3-305 apply to all applications started on or after 1 December 2019 ^{[37, 38]}.

Chicago stormwater rules shape the plan directly. Land areas separated by public right of way at the end of development are not substantially contiguous. Rate control is not required for projects discharging directly to Lake Michigan, though every other standard still applies. Volume control applies to every regulated development except new roofs on a vertical addition. The initial submittal is signed by the applicant, sealed by a Professional Engineer and filed through the DOB Express Permit Program and E-Plan (ProjectDox) ^[9]. The Department of Water Management's 2026 Regulations for Sewer Construction and Stormwater Management are the current technical text ^[39]. Inside the city, an MWRD permit is required only for impacts to MWRD facilities ^[3]. For a sense of the scale of current city work, see the studio's notes on the United Center redevelopment and the North Michigan Avenue revamp.

Suburban Cook County and MWRD

Two Cook County conditions move the layout. MWRD's Technical Guidance Manual notes design constraints on retention practices "due to the prevalence of soils with poor infiltration rates throughout Cook County," and requires them to drain to two inches above the bottom of the practice within 72 hours ^[40]; volume control often has to come from storage, which takes land. And a municipality straddling Cook and a neighboring county remains under the full WMO in its Cook portion unless it holds an intergovernmental agreement with MWRD, even if it has adopted the neighbor county's ordinance ^[41]. Article 14 lets qualified Authorized Municipalities issue watershed permits locally ^[3].

Downstate and the Metro East

Rockford, Springfield, Champaign, Peoria and the Metro East counties of St. Clair and Madison lie outside the five collar counties that received countywide stormwater powers under 55 ILCS 5/5-1062 ^[10], and their review bodies, fees and clocks are set by each city and county. The same statewide rules still apply: the 25,000 home rule line ^[6], the 1.5 mile plat reach ^[8], ILR10 ^[14], the CDB baseline ^[12] and the IDOT District office for state routes ^[2]. The service areas page lists where the studio works.

Asset registries

RV parks, campgrounds and glamping. The OHI and ARVC state rules list, a secondary source, names the Illinois Department of Public Health as the campground licensing agency ^[42]. Locally, an Illinois RV park or campground is a zoning special use in most counties, frequently a discretionary approval. The same holds for tents, cabins and yurts on a glamping site plan: classification is a local zoning and building permit question. The studio's state-by-state RV park matrix sets Illinois beside the states that publish hard caps.

Car washes. Illinois has no car wash statute; the state-level constraint is discharge, not water supply. In Cook County, sanitary discharge falls under MWRD's Pretreatment and Cost Recovery program ^[43]. Local codes set the queue. In St. Charles, Table 17.24-3 of the zoning code requires 10 stacking spaces at 9 x 20 ft in a single line; a car wash is permitted in the BR district, but the drive-through component requires a Special Use under Sec. 17.04.330, with a public hearing, mailed notice and six findings of fact that must all be affirmative ^[44]. The Club Car Wash staff report of 5 May 2026 shows the plan at work: dual pay lanes each hold 12 to 13 cars before merging after the pay station, and the report counts 26 to 28 stacking spaces provided against a 10-space code minimum, with a projected 80 PM peak hour trips (40 in, 40 out), and staff reviewed the project against comprehensive plan policies "relevant to review of the Concept Plan" ^[44]. A car wash site plan for the Chicago suburbs starts from those facts; which stages take an unsealed concept plan is covered in where unsealed site plans are accepted.

Fuel, c-stores and truck stops. The sequence is the OSFM tank permit with a certified installation contractor, the canopy and dispenser layout under the local building code, the IDOT or county driveway permit, and the stormwater permit. Any site with tank history needs a check for a recorded NFR letter, because its engineered barriers fix where the new plan can dig ^[27]. See the gas station and truck stop hubs, and the studio's guide to gas station permitting, tanks and traffic.

Self storage and multifamily. No state licensing layer applies. In Cook County detention applies to a non-residential parcel of 3.0 acres or more once new development there totals 0.50 acre or more in the aggregate, counting everything developed since 1 May 2014 ^[3]. MWRD groups multi-family with non-residential at the 0.50 acre volume control and 3.0 acre detention parcel sizes, rather than the 1.0 and 5.0 acre subdivision thresholds ^[3]. An impervious-heavy self storage campus hits that line early.

Hotels. A hotel is Group R-1 under the IBC as adopted locally or under the CDB baseline, and its accessible route from parking to entrance falls under the Illinois Accessibility Code as well as the ADA ^[13]. If the program includes a public pool, only architects and structural engineers may design its structural portions, and professional engineers are required for its mechanical and electrical systems ^[1]. See the hotel site plan hub.

Marinas. Construction in public waters runs through IDNR's Office of Water Resources under 615 ILCS 5, alongside US Army Corps Section 404 and Section 10 permits; in Cook County, new or reconstructed outfalls to waterways or Lake Michigan need an MWRD permit, and MWRD operates the Chicago Area Waterway System ^{[15, 3, 45]}. Fuel dock tanks fall under OSFM ^[16]. See the marina site plan hub.

Industrial, warehouse and flex. No state licensing layer applies; the binding constraints are local zoning, the detention thresholds and IDOT access. See the industrial, warehouse and flex space hubs, and the small-bay industrial model project in Grove City, Ohio for a comparable Midwest layout.

Timelines and bottlenecks

On a state route with a signal or turn lane, IDOT starts first and finishes last. Stormwater review runs in parallel but has its own loop, and in Cook County every MWRD resubmittal takes 15 working days ^[3]. The ILR10 Notice of Intent asks whether state historic preservation and endangered species compliance has been achieved, through coordination with SHPO and IDNR or through interagency agreements ^[24].

The review cycles that Illinois costs and most states do not:

1. A site plan on a survey underlay without a professional land surveyor's seal ^[1].
2. A retaining wall detail sealed by a professional engineer rather than a structural engineer ^[1].
3. A missing Professional Design Firm registration number on the cover sheet ^[1].
4. The wrong rainfall bulletin: Bulletin 75 for MWRD, Bulletin 70 in the IDNR model ordinance ^{[3, 11]}.
5. Cook County detention sized without the area developed since 1 May 2014 ^[3].
6. Volume control designed around infiltration in Cook County soils ^[40].
7. Multi-family treated as residential under the WMO ^[3].
8. Schedule R not on file before MWRD permit issuance ^[3].
9. A Chicago building or sewer permit sought before stormwater approval ^[9].
10. A village's 1.5 mile plat jurisdiction missed on an unincorporated parcel ^[8].
11. A municipality on the Cook line assumed to be outside the WMO ^[41].
12. A rural site scoped as if no code applied ^[12].

Proof points

Population. Illinois had 12,719,141 residents on 1 July 2025, up 16,108 over the year and the third consecutive year of growth, with net domestic out-migration of 40,017, the lowest in 15 years ^[46]. Growth is concentrated: 15 of 102 counties gained population from 2020 to 2024, including Kendall, Champaign, Grundy, McHenry and Will ^[47].

Will County logistics. CenterPoint Intermodal Center at Joliet and Elwood is built on the former Joliet Army Ammunition Plant site ^{[48, 49]}. Will County holds countywide stormwater authority under 55 ILCS 5/5-1062 ^[10], and it is one of the counties that gained population ^[47]. The studio's notes on flex space and industrial trends cover the demand side.

Chicago planned development. The Planned Development application for 11400 to 11458 S. Halsted in the Chicago Plan Commission's published materials shows the PD sequence in practice, from the installment fee structure to the courtesy presentation before site plan approval ^[36].

Suburban car wash. In the Club Car Wash case before the St. Charles Plan Commission on 5 May 2026, the code required 10 stacking spaces, and staff accepted two lanes that each met the required count ^[44].

Working across the state line

Illinois projects often sit in a regional pipeline. The Iowa, Wisconsin, Indiana and Missouri pages set out the neighboring states' approval layers. For the full service, start at site plan services.

By Viola Sauer, Principal, Innowave Studio