Concrete and Paver Patio Permits: Drainage and Lot Coverage

You treat the backyard slab like landscaping.

Pavers go down over a weekend, the concrete crew pours a 20-by-20 pad, and nobody mentions the building department—until a neighbor complains about runoff, the HOA asks for a stamped plan, or the city flags lot coverage. That is when "just flatwork" turns into a patio permit, a grading sign-off, or an impervious-cover problem.

This guide is for uncovered concrete and paver patios at grade: flatwork, drainage, and how cities count hard surfaces toward lot limits. It is not a patio-cover or pergola guide (see pergola and patio cover permits), not a driveway curb-cut / right-of-way guide (see driveway curb-cut and ROW permits), and not a general grading megaguide. Rules are local. PermitCove is an independent homeowner guide—not a government agency. Confirm with your AHJ before you dig.

What counts as a patio / flatwork

Most cities treat a patio as an open-air leisure surface at or near existing grade—brick, block, pavers, stone, or concrete. Prince George's County, Maryland, defines patios that way on its residential patio page: masonry leisure areas of brick, block, pavers, stone, or concrete.

In plain English, that usually includes:

• Poured concrete slabs (plain, stamped, or broom finish)
• Interlocking or loose-laid pavers over a compacted base
• Brick, flagstone, or other at-grade hardscape used as a patio

It is a different animal from a raised deck, a roofed porch or screened porch, or a driveway apron that meets the street. If your patio sits on top of a retaining wall or a tall seat wall is part of the design, you may also need wall review—see our retaining wall permits guide.

Planning a fire pit on the new patio? See fire pit permits and setbacks.

When cities typically require a patio / flatwork permit

There is no single national square-footage rule. Cities publish their own size thresholds, then add "always require a permit" triggers for height, utilities, and fire features. A few published examples:

Notice how different those are: Lombard can trigger at 100 square feet, while Naperville and Prince George's publish a 500-square-foot pattern for many at-grade slabs. "My neighbor poured without a permit" is not a substitute for reading your local handout.

If you are just starting, run the 10-minute AHJ permit checklist and ask specifically about flatwork, patio, or hardscape—not only "building permit."

Drainage and grading: the part that fails inspections

Cities care where the water goes after a hard surface replaces lawn. Positive drainage away from the house and away from the neighbor is the theme across patio handouts.

• Naperville requires a Patio Grading Certification (owner and contractor). Positive drainage within roughly 2%–25% slopes, consistent with the subdivision master grading plan, and not adversely affecting neighbors. A detailed PE grading plan may be required if the patio is within 5 feet of an easement, within 15 feet of a property line, includes vertical elements such as seat walls, has site constraints, or has historical drainage issues.
• Lombard calls for a minimum slope of 1% and a maximum of 8%, drainage that does not adversely affect adjoining properties, and notes that within 5 feet of a property line you may need a 2-inch curb. The patio surface is generally expected to match existing ground elevation unless a private development engineer approves otherwise in writing.

Call 811 before digging. Naperville also notes that underground electric service is not permitted under a deck or patio, and meter relocation—if needed—is at the owner's expense.

Impervious cover, lot coverage, and open-space limits

Even when the building counter says "no patio permit," zoning or stormwater rules may still limit how much of the lot you can pave.

• Lombard: Most single-family residential lots must maintain 50% open space (lawn, garden, natural area). Patios do not count as open space.
• Ann Arbor, MI: Impervious surfaces include rooftops, walkways, decks, patios, courtyards, driveways, concrete/asphalt, gravel roads, and compacted surfaces that impede infiltration. Stormwater management is required on 1–2 family residential when you increase impervious area by 200 square feet or more. If new impervious is ≥200 sq ft, the worksheet's First Flush storage is new impervious square feet × 0.08 = cubic feet required, and the worksheet goes with the grading permit.
• Austin, TX: Impervious cover counting includes building coverage, paved areas, walkways, and driveways; uncovered patio is a line item, and AC pads and other concrete flatwork count. Uncovered wood decks with drainage spaces over a pervious surface are commonly counted at 50% of horizontal area (see Austin's residential measuring worksheets and LDC 25-1-23 related rules). A common residential max is often around 45%, but it varies by zoning district—some small-lot and other districts allow higher. Check your zoning district; do not assume every Austin lot is 45%.

Pavers with open joints can still count as impervious if the base or joints do not infiltrate the way your city defines "pervious." Ask how your AHJ scores the product you are buying—do not assume "pavers = permeable credit" without their worksheet.

Packet checklist (what to bring)

Composite from Naperville, Prince George's County, and Lombard patio materials—adapt to your local checklist and use how to apply for a building permit for the process habits:

1. Signed permit application
2. Legal plat of survey (or site/plot plan) with the patio drawn to scale, distances to property lines, and nearby utilities/windows called out
3. Photos of rear and side yards (Naperville asks for photos of rear/sides and the electric meter about 10 feet each side)
4. Patio grading certification or drainage notes (owner + contractor where required)
5. Cross-section of the paving system (example: Naperville concrete — minimum 4" slab over minimum 4" compacted gravel base; Lombard concrete — 4" compacted aggregate CA-6 plus 5" six-bag air-entrained concrete with 6×6 wire mesh)
6. Stairs/landings plans if elevation changes
7. Contractor information (Prince George's expects an MHIC-licensed contractor unless the homeowner erects the work)
8. Separate electrical (and plumbing/gas) permit applications if you are adding fixtures, outlets, or a fire feature with utilities
9. HOA architectural approval letter if your association requires it—separate from the city/county permit

Post the permit where required. Naperville invalidates the permit if work does not commence within 180 days, requires the permit displayed in a window, and asks you to schedule inspections with 72 hours' notice at 630/420-6100 option 1. Lombard requires a pre-pour inspection—do not bury the base until they see it.

Common fail patterns

• Treating any uncovered slab as "landscaping only," then hitting a 100 or 500 sq ft threshold you never checked
• Adding a fire pit, gas grill stub, or outlets after the fact—utilities and permanent fire features flip many "small patio" exemptions
• Building more than about 30 inches above adjacent grade without treating it like a raised structure (Naperville's height trigger)
• Draining toward the neighbor or ignoring master grading / open-space limits
• Pouring over easements or too close to property lines without the PE plan the handout called for
• Skipping septic-access review on well/septic lots (Prince George's)
• Counting on HOA approval alone—or city approval alone—when you need both
• Pouring before the pre-pour inspection

FAQ

Do I need a permit for a small concrete patio?

It depends on your city. Lombard requires permits at 100 square feet or greater (and sooner in easements or with utilities). Naperville and Prince George's publish under-500-square-foot patterns for many at-grade patios—but both still impose setbacks, and Naperville still requires a permit for fire features, height over 30 inches, and electrical/plumbing/gas. Read your handout, not a neighbor's story.

Do pavers need the same permit as poured concrete?

Usually yes when the surface is a patio. Prince George's lists brick, block, pavers, stone, or concrete together. Zoning and impervious-cover counting often treat both as hardscape.

Is a patio the same as a patio cover?

No. An uncovered slab or paver surface is flatwork. A roofed structure is a patio cover or pergola project with different load and zoning rules—use the pergola and patio cover guide.

What if my lot is already near its impervious or open-space limit?

You may need stormwater storage (Ann Arbor's First Flush math when you add 200+ sq ft), a smaller footprint, permeable products your city actually credits, or a redesign. Austin homeowners should check the zoning district's impervious-cover maximum rather than assuming a single citywide percentage.

Can the homeowner pull the permit?

Often yes for owner-built work, but some counties require a licensed contractor (Prince George's references MHIC licensing unless the homeowner erects). Ask who must be the applicant before you schedule the pour.

Bottom line

Uncovered concrete and paver patios look like landscaping, but cities regulate them as flatwork with size thresholds, drainage certifications, and impervious or open-space math. Check square footage, height, utilities, fire features, easements, and lot-coverage worksheets before the base goes in. Bring a scaled site plan, a cross-section, and grading notes that protect the neighbor. Confirm every number with your AHJ—this guide shows how published cities draw the lines; it does not replace your local permit counter.

Official sources

• City of Naperville — Residential Patio/Athletic Court Permit (PDF, revised 06/23/2023)
• Prince George's County, MD — Patios
• Village of Lombard — Patios handout (PDF)
• City of Ann Arbor — Impervious Area Worksheet for Residential
• City of Austin — HOME amendments (Development Services)
• City of Austin — Residential permit / impervious cover worksheet example

We research public city, county, and state building-department pages and translate them into plain-English checklists. We are not a government agency and this is not legal advice.

Edited by Ahmed Khalifa, founder of PermitCove. Sources are linked inline; see our Editorial Policy.