Basement Excavation in Chicago: What It Takes and What It Triggers

Digging out a Chicago basement means excavating beside and below a building that is still standing on that ground, so it is a structural job first and an excavation job second. It triggers permits, drawings from an Illinois design professional, a call to 811 Chicago, and a close look at the neighbors' walls. We can tell you what the City's rules say and what the job touches. We won't give a generic method here, because the right way to carry a wall depends on your building and your soil, and that is an engineer's call.

What does "digging out a basement" actually mean?

People use the phrase for several different jobs, and the paperwork differs for each:

• Lowering an existing basement floor to gain headroom. The foundation walls stay, but what supports them changes.
• Excavating a crawl space or partial basement to make a full one.
• Digging out a new basement under an addition or a rebuilt building.
• Excavating outside a foundation wall for repair or drainage. That is a different job, covered in foundation repair in Chicago.

The first two are the hard ones. The building is already loaded, and every inch of depth you add changes the load path of the soil beside and below the footing. We don't state a safe depth or a standard method. Check with the Department of Buildings, and hire a structural engineer to design it.

Do you need a permit to dig out a basement in Chicago?

Almost certainly yes, because this is not the kind of site work the City exempts. The basic rule is that a building permit is required before beginning most construction, demolition, rehabilitation and repair work, with a limited range of site work, nonstructural repairs and minor alterations exempt (City of Chicago).

The City's excavation exemption is narrow. There is no building permit for grading or excavation no deeper than 5 feet below grade on private property, or no deeper than 10 feet if the work is not within 5 feet horizontally of an existing structure or the public way (City of Chicago). A basement dig is, by definition, near and under an existing structure, so it does not fit the second exemption. And altering what carries a building's weight is not a grading job.

We can't tell you your project's exact permit path. Ask the Department of Buildings, or have us run it through our permit process. Our excavation permit depth rules article explains the thresholds in detail.

Why drawings are part of the job

The City's Standard Plan Review permit is the process for plan-based work, and it lists foundations and excavation of not more than 12 feet deep among the types of projects it covers. It requires an architect to prepare the drawings, submits through E-Plan, and requires zoning approval for all projects (City of Chicago).

Plan-based permits require plans prepared by an Illinois-licensed architect or engineer, and for most projects that means an architect or a structural engineer (City of Chicago). So a basement lowering is a design job. Expect the drawings to show what you are changing, what supports what, and how the work is staged.

If the excavation would go beyond the range that program lists, ask the Department of Buildings which review applies. We don't state a different threshold because we haven't confirmed one.

The 811 call comes first

Before any non-emergency excavation in Chicago, you call 811 Chicago (DIGGER), a free service run by CDOT, with at least two business days of notice, excluding weekends and holidays (City of Chicago). The call applies to homeowners, including on private property (City of Chicago). State law adds hand or vacuum excavation within the tolerance zone around marked lines (220 ILCS 50). A basement dig has lines to find: water service, sewer connections, gas, electric and anything else entering the building near the area you are opening.

Our Chicago DIGGER 811 article has the full rules and the difference between DIGGER and JULIE.

Who is allowed to do the work

Chicago permit rules say an individual without a general contractor license cannot perform or oversee work needing a demolition permit or excavation notice (City of Chicago). Plan on a licensed general contractor and an engineer. A contractor who offers to dig your basement out without drawings or a permit is carrying a risk that ends up on you.

What soil, footings and water are asking for

Soil and water decide what is possible. The National Ready Mixed Concrete Association (NRMCA) advises assessing soil conditions, and notes footings must bear on undisturbed or well-compacted soil (NRMCA). It also recommends drain tile or pipes around the exterior footing and exterior-side waterproofing for poured basements. When you lower a floor, that footing zone is exactly what you are exposing.

Water management is part of the design, not a finishing touch. The University of Minnesota Extension says to slope soil away from the foundation at least 1 inch per foot for at least 6 feet, and to discharge downspouts at least 4 feet from the wall (UMN Extension). Those numbers are general guidance, not a Chicago code rule, but they show why grading and downspouts get reviewed in any basement project.

We don't make claims here about Chicago soil type, frost depth or minimum footing depth. Those need an engineer's site-specific input and a check with the Department of Buildings.

What it does to the walls you already have

Existing basement walls may show cracking before work starts. NRMCA says some cracking in poured basement walls is normal, from shrinkage, corners at openings, pour lines and settlement, and that typical builder warranties require repair only if cracks leak, show measurable vertical displacement, or exceed 1/8 inch (NRMCA). That is guidance on new poured walls and does not describe how an old Chicago masonry foundation will behave.

The point for planning is to document the existing conditions before anyone digs. Photos, crack locations and the state of the masonry above are all part of a good scope. If the walls are old brick or stone, ask about masonry repair before or during the dig.

What it does to the neighbors

On Chicago lots, the next building is often only a few feet away, and many are attached. Digging near a shared wall or the lot line carries real risk of movement and damage to the neighbor's property. We cover this in digging next to a neighbor's wall. The City's demolition rules require bracing certification or the neighbor's written consent when an adjoining structure is affected (City of Chicago), and that is a good sign of how seriously the City treats adjoining structures. For excavation, check with the Department of Buildings on what applies.

What the job puts in the street and alley

A basement dig produces a lot of soil. Hauling it out puts trucks and dumpsters in front of the building. Using the street, alley, sidewalk or parkway for materials, scaffolding or a dumpster needs a separate CDOT permit (City of Chicago). Who pulls that permit, and who pays, should be written in your contract.

What to ask before you hire anyone

1. Who designs this, and can I see the engineer's drawings before the work starts?
2. Who pulls the building permit and the public way permit? What are the numbers?
3. Has 811 Chicago been called, and are the marks in?
4. How is the existing foundation supported at each stage?
5. What is the plan for drainage, waterproofing and the new floor?
6. How are my neighbors' walls protected, and who documents their condition?
7. What is excluded from this bid?

If any answer is "we'll figure it out when we get there," that is a reason to keep looking. Our excavation crew works with engineers on Chicago lots and handles the permits, the 811 call and the dig. For the bigger picture of permits, utilities and foundations, see the excavation and foundation guide.

Common questions

This article explains general rules and common situations in Chicago. It is not legal advice, and City rules change. For a specific property, check with the Chicago Department of Buildings or a licensed professional.