Chicago Flat Roof and Shingle Roof Guide

A flat roof in Chicago is rarely flat. It is a low-slope roof, built to move water to a drain, and nearly every failure we see comes from water that stopped moving. A shingle roof works on a different principle: the steep pitch sheds water, and the shingles and flashing keep the rest out. Which kind you have decides your materials, your permit path and the kind of repair that makes sense.

This guide covers both roof types end to end for a Chicago owner: how roofs fail, how to tell repair from replacement, what the City permit rules say, what license your roofer must hold, and how to hire. Each section links to a deeper article. We are honest where the facts are thin. Where we haven't verified a rule, we say so and send you to the Department of Buildings.

If you only read one part, read this:

1. Find the water. A leak is where water shows up, not necessarily where it comes in. Ponding, failed flashing and clogged drains cause most flat roof problems.
2. Know your roof type. Low-slope and pitched roofs have different permit rules in Chicago.
3. Check the license. Illinois requires a roofing license, and a permit applicant using an unlicensed roofer isn't eligible for the City's Express reroofing permit.
4. Get the scope in writing, including what gets torn off, what gets fixed underneath and who pulls the permit.

Do you have a flat roof or a shingle roof?

Most Chicago two-flats, three-flats, greystones, courtyard buildings and storefronts have a flat or low-slope roof. Most bungalows and many single-family homes have a pitched roof covered in shingles. Some buildings have both, such as a flat main roof with a pitched porch or dormer roof.

For permit purposes, the line the City draws is pitch. The City's permit guide treats pitched roofs at 2:12 or steeper differently from low-slope roofs (Guide to Building Permits). If your roof is low-slope, almost every roofing job, even on a residential building up to four stories, needs a permit. We cover that in detail below.

Flat and low-slope roofs use a membrane. The National Roofing Contractors Association groups the membrane types as built-up roofing (BUR), polymer-modified bitumen, rubber sheets (EPDM), thermoplastic sheets (TPO and PVC), sheet metal and sprayed urethane foam (NRCA). On Chicago two-flats the common ones are modified bitumen (often called torch down), EPDM rubber and TPO. See TPO versus EPDM for a Chicago flat roof and torch down on a Chicago two-flat.

Shingle roofs use overlapping asphalt shingles over an underlayment on a pitched deck. See shingle roof replacement on a Chicago bungalow.

Our roofing services page covers both types. Akats is licensed and insured in Illinois, and roofing is one of the 11 trades we do in-house.

How do Chicago flat roofs fail?

Most flat roof failures fall into five groups.

Ponding water. The Asphalt Roofing Manufacturers Association defines ponding on a low-slope roof as water that remains on the roof 48 hours or longer. ARMA says it can overload the deck, grow algae and vegetation, clog drains, speed up membrane deterioration and wet the insulation. It recommends at least 1/4 inch per foot of slope, and the NRCA Roofing Manual it quotes recommends positive slope through a sloped deck or framing, tapered insulation, and proper placement of drains, scuppers and gutters (ARMA). Our deeper articles are ponding water on a flat roof and why water sits on Chicago roofs.

Drainage that doesn't drain. ARMA also notes that crickets (small sloped saddles) upslope of rooftop equipment and along low points between drains reduce localized ponding, and that secondary overflow drains may be required by local plumbing code (ARMA). See what a cricket is.

Failed flashing and edges. The roof edge, parapet wall, chimney and pipe penetrations are where most leaks start. The Brick Industry Association says flashing belongs at the tops of walls, parapets and chimneys (BIA Technical Note 7), and that caps and copings on top of walls need to shed water (BIA Technical Note 36A). When a coping lifts or a parapet flashing tears, water goes behind the membrane and into the wall. See when parapet flashing fails.

Membrane damage. Open seams, punctures, blisters and splits let water in. See why a flat roof bubbles or blisters.

Winter and snow. Chicago averages 38.4 inches of snow a year, based on 1991 to 2020 normals (NWS Chicago). Snow sits on a flat roof until it melts, and meltwater finds any weak spot. We've kept snow load and ice dams to short explainers because we haven't verified Chicago numbers for either. See flat roof snow load and ice dams on Chicago roofs.

For the leak itself, start with why Chicago flat roofs leak, and where to look first, then read finding and fixing a flat roof leak.

What are the warning signs your roof needs attention?

Check from the ground, from the attic or top floor, and (only if it is safe and you can access it) from the roof:

• Water stains, bubbling paint or damp plaster on ceilings and upper walls.
• Puddles that are still there two days after rain.
• Blisters, splits, open seams or exposed fabric on a flat membrane.
• Missing, curled or cracked shingles, or shingle granules collecting in gutters.
• Flashing that has lifted, rusted or pulled away at a wall, chimney or vent.
• Loose or cracked coping at the parapet, or mortar failing around the roof edge. See our brick and masonry repair guide.
• Clogged drains, scuppers or downspouts.
• Daylight in the attic, or a musty smell upstairs.

Don't walk a wet, icy or steep roof. Photograph what you can from a window or the ground, and have a roofer look. Our flat roof fall and spring checklist puts the seasonal walk-through on one page.

Repair, coat or replace: how do you decide?

Here is the honest sequence, from least to most work:

1. Spot repair. A torn seam, a bad pipe boot or a lifted flashing can often be fixed in one visit if the membrane and deck underneath are sound. See flat roof: repair or replace.
2. Coating. Coating can slow wear on a membrane that is still sound and well attached. It can't fix wet insulation or a rotted deck. See can you coat a flat roof instead of replacing it.
3. Recover. A new membrane over the existing roof, where the City's rules allow it and the existing roof is dry.
4. Tear-off and replacement. Everything above the deck comes off, wet material is replaced, and the roof is rebuilt to slope and drain properly.

We don't put a number of years on any roof here. Manufacturer pages publish warranty terms, not measured service life. For example, Carlisle SynTec describes one of its EPDM systems with a long non-prorated material warranty, and that is a warranty and specification term (Carlisle SynTec). A warranty tells you what a manufacturer will cover, not how long your roof will last on a Chicago building. See how long a flat roof lasts in Chicago weather for how we talk about it.

What does push a roof toward replacement:

• Wet insulation, which a surface repair won't dry out.
• A soft or sagging deck.
• Failure in many places at once, not one defect.
• Water ponding because the roof lacks slope.
• Repair after repair in the same area.

Related: what drives flat roof replacement cost in Chicago.

What are the flat roof membrane options?

You will hear four main names.

• Modified bitumen (torch down). Asphalt-based sheets. Johns Manville says its SBS modified bitumen can be installed by cold-applied, heat-weld (torch), self-adhered, mechanically fastened or hot-applied methods (Johns Manville). Torch application brings open flame to a building, so ask about fire safety.
• EPDM. A rubber sheet. Johns Manville offers EPDM with factory in-seam tape, which matters because seams are where many flat roofs fail (Johns Manville).
• TPO. A thermoplastic sheet formulated for heat-welded seams (Johns Manville).
• Built-up roofing (BUR). Layered asphalt and felts, the traditional tar-and-gravel roof (NRCA).

Which is best depends on the building, the substrate, access, the parapet and drain layout, and the roofer's experience with it. Reflective ("cool roof") systems exist, but we haven't verified Chicago's reflectance requirements, so we don't state any numbers. For comparison articles, see TPO versus EPDM and torch down roofing.

If you want a rooftop deck, read putting a deck on a flat roof first. An unpermitted rooftop feature makes the building ineligible for the City's Express reroofing permit (Guide to Building Permits).

What about shingle roofs?

A pitched roof sheds water faster, so shingle roofs tend to fail at the details: flashing at walls and chimneys, valleys, vents and the edges. Missing or lifted shingles, granule loss and sagging decking are the common signs.

For homeowners, three questions come up most:

• Can I roof over the old shingles? The City's Express reroofing permit allows a recover over one existing layer, and requires drawings from an architect or structural engineer to add a layer over two or more (Guide to Building Permits). We have not verified whether the code sets an absolute cap on layers, so check with the Department of Buildings. See can you roof over old shingles in Chicago.
• When is the best time to replace? Weather and scheduling both matter. See best month to replace a roof in Chicago.
• What does a bungalow replacement involve? Tear-off, deck repair, underlayment, flashing, shingles and ventilation. See shingle roof replacement on a Chicago bungalow.

We haven't verified slope minimums or ice and water barrier details for Chicago, so we don't state them here. Your roofer should be able to show you the manufacturer's installation instructions for the shingle they use.

Do you need a permit to repair or replace a roof in Chicago?

It depends on the roof type and the size of the job, and the City's rules are specific.

Small repairs: no permit. A permit isn't required for roof repair limited to 25 percent of the roof area (patching) on any building, as long as no part of an exterior wall or roof is cut away (Guide to Building Permits).

Pitched roofs on residential buildings up to four stories. The City lists roof repair, recover and replacement as no permit when the roof pitch is at least 2:12. Structural repair is not included (Guide to Building Permits).

Low-slope roofs: permit required. A permit is required for any structural roof repair and any work on low-slope roofs, even on residential buildings up to four stories (Guide to Building Permits). That is the rule that catches many flat roof owners by surprise.

Express Permit reroofing. The City's Express Permit Program has a Reroofing worktype (Guide to Building Permits). Eligible work includes roof repair limited to 25 percent of the roof area, a recover over one existing layer, and roof replacement with no structural work. With drawings by an Illinois architect or structural engineer, Express also covers an additional layer over two or more existing layers, and structural repairs to the roof structure. Not eligible: anyone without a valid Illinois roofing contractor license doing the work, a building with an unpermitted rooftop feature such as a roof deck, materials or methods that don't meet Building Code minimums, and work that doesn't meet the Energy Transformation Code insulation minimums (Guide to Building Permits).

Emergencies. Emergency work that normally needs a permit may be done first to prevent imminent harm, with the permit application submitted the next business day (Guide to Building Permits). Work in the public way, such as a dumpster in the street or alley, needs its own CDOT permit (Guide to Building Permits).

Permit rules change. Confirm with the Department of Buildings before you sign. Our full guide is Chicago roof permit: what needs one and what doesn't, with a short version in do you need a permit to patch a roof.

What does Chicago require when you re-roof?

The City says reroofing must meet the Chicago Energy Transformation Code insulation minimums, and that Express reroofing isn't available for work that doesn't comply (Guide to Building Permits). The City cites the residential and commercial sections of the Energy Transformation Code in its permit instructions.

What we don't state: specific R-values, reflectance numbers or a cap on layers. We haven't verified them from the code text, and a wrong number is worse than none. Ask your roofer to show the insulation plan in writing, and confirm with the Department of Buildings. We cover what we can verify in what Chicago requires when you re-roof.

Who is allowed to roof your building?

Two licenses can come into play.

Illinois roofing license. It is unlawful in Illinois to provide professional roofing services or hold yourself out as a roofing contractor without a license from IDFPR, the Illinois Department of Financial and Professional Regulation. Roofing and waterproofing work may be done only by a licensed roofing contractor or qualifying party, and roofing contractors may subcontract only to licensed roofing contractors (Roofing Industry Licensing Act).

The license has two types: limited, for residential properties of 8 units or less, and unlimited, for residential, commercial and industrial. Applicants need liability and workers' compensation insurance, an unemployment insurance account, a continuous bond and a qualifying party who passes the exam (Illinois General Assembly). There are exceptions, such as a person doing roofing work on their own property. A permit issuer must confirm the contractor is licensed before issuing the permit, and municipalities keep their power to regulate roofing through permits, fees and inspections (Illinois General Assembly).

Chicago general contractor license. A reroofing permit also requires a Chicago-licensed general contractor, unless the owner qualifies as an owner-contractor, and the contractor or roofing subcontractor must hold a valid Illinois roofing license (Guide to Building Permits).

You can check roofers on IDFPR's lookup, and Chicago contractors on the City's lookup (Department of Buildings).

What drives the cost of a roof job?

We don't publish prices. These are the factors that move the number:

• Roof size and shape, including parapets, skylights, penetrations and multiple levels.
• What's underneath. Wet insulation, a damaged deck or layers to tear off.
• Slope and drainage fixes. Tapered insulation, new drains or scuppers, crickets.
• Material and system. The membrane or shingle, the attachment method and the warranty tier.
• Insulation requirements under the Energy Transformation Code.
• Flashing, coping and masonry at the roof edge, which is often mason work.
• Access. Dumpster placement, hoisting and public way permits.
• Permit and engineering costs, when drawings are required.
• Season and weather. Cold, wet or windy conditions limit what can be installed.

See what drives flat roof replacement cost.

How do you hire a roofer in Chicago?

Before you sign, ask for:

1. An Illinois roofing license number, and check it with IDFPR. Ask about the Chicago general contractor license too (Department of Buildings).
2. Proof of insurance, including workers' compensation.
3. A written contract. Illinois requires a signed written contract or work order for home repair over $1,000 on a residence of 1 to 6 units, with the total cost and materials (Illinois Home Repair and Remodeling Act). The Act lists roofs among its examples (Illinois General Assembly).
4. The permit plan. Who pulls it, and when work starts relative to issuance. Permits expire if the first inspection isn't passed within 540 days of when work may begin (Guide to Building Permits).
5. The scope below the surface. What happens if the deck or insulation is wet when the old roof comes off.
6. Photos. Before, during and after, especially of anything that gets covered.

Be careful with anyone who wants to start without a permit on a low-slope roof, or who offers a fix that doesn't address where the water enters.

When should you call us?

Call when you see a ceiling stain, a puddle that doesn't drain, a torn or lifted membrane, damaged flashing, missing shingles or a failed coping. Call right away after storm damage. We look at the roof, the drains and the edges, give you a written estimate and tell you if a repair is enough.

Call 312-339-9627 or ask for a free estimate, in English or Spanish. If the City has flagged your roof or exterior, our team handles the repair and the paperwork. Start with what a Chicago violation notice says. And if your question is whether your roof job needs a permit, the Department of Buildings has the last word.

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.