Does a new driveway, patio or walkway trigger stormwater rules in Pennsylvania?

Updated November 11, 2026 · KeystoneProGuide editorial team

Can a new patio or driveway need stormwater approval?

It can, depending on where you live. The rules are not statewide. Each municipality writes its own stormwater ordinance, and the size of new hard surface that triggers it varies from place to place. Check with your township or borough before the work is priced, not after it is poured.

Why does paving matter for stormwater?

Because water cannot soak through it. Penn State Extension explains that traditional paving surfaces are impervious: rain and melting snow cannot pass through into the soil, so they run off instead. Stormwater from built-up areas is collected by separate storm sewer systems, which discharge it into local streams and rivers without treatment.

Those systems are regulated. Penn State Extension says Philadelphia and Pittsburgh have been in the state's MS4 program since the 1990s, and around 950 other systems had been enrolled by 2018, under permits from the Pennsylvania Department of Environmental Protection. Every MS4 program includes post-construction stormwater management, meant to keep new buildings, parking areas and other development from creating future problems. Municipal ordinances carry this down to individual properties; Upper Darby's, for instance, lists meeting certain MS4 permit requirements among its purposes.

How does a township count new paving?

Upper Darby Township in Delaware County is a worked example. Its ordinance applies to "all activities that may affect stormwater runoff", and it measures "regulated impervious surface", meaning new, additional or replacement hard cover. Its thresholds:

The total is cumulative. The ordinance's own example starts with a 150-square-foot shed, which is exempt. A later 499-square-foot room addition brings the total to 649 square feet and the simplified method. A 700-square-foot pool and patio after that brings the total to 1,349 square feet and the full requirements for all of it. Repaving without reconstruction is listed as exempt. The township may withdraw exemptions where a drainage problem is known downstream, and an exemption never removes the duty to protect neighboring property. Erosion and sediment control under state rules applies regardless.

Upper Darby's numbers are its own. Your municipality's ordinance may use different thresholds, a different starting date and different definitions, so ask for the stormwater section that applies to residential projects.

What size is a typical patio or driveway?

For scale, Angi's patio guide starts its size table at a 7-by-7-foot slab of 49 square feet and prices a 10-by-10-foot patio, 100 square feet, at $600 to $1,600. Its driveway guide lists common sizes including 12 by 24 feet (288 square feet) and 24 by 24 feet (576 square feet). Under a cumulative count like Upper Darby's, a driveway widening plus a patio can cross a threshold that neither would alone.

What about Philadelphia?

The city sets its own limits through its permit rules. A building permit is required for any project with 5,000 square feet or more of earth disturbance, and a separate Site Permit is required for earth disturbance over 1,400 square feet on steep slopes in the Steep Slope Protection Area, or over 500 square feet in the Wissahickon Watershed Overlay, except on sites designated Category 5. For smaller jobs, the city says sidewalks and driveways that stay out of the public right-of-way and include no parking often need no building permit, unless the property is on the historic register.

Does the state building code require a permit for paving?

The Uniform Construction Code regulation exempts sidewalks and driveways that are 30 inches or less above the adjacent ground and not built over a basement, as long as the work does not violate a law or ordinance. That last condition is where a municipal stormwater ordinance comes in: the building code exemption does not override it.

Are there paving options that reduce runoff?

Yes. Penn State Extension describes porous pavement and permeable pavers, specially designed concrete, asphalt and paving stones that let rain and snowmelt drain through. They must be installed over a carefully prepared base, at least graded washed stone and sometimes pipes and storage below. They need regular cleaning, often by vacuuming, to stay open, and a system not designed for heavy loads can fail; the extension service shows one that collapsed under truck traffic.

For homeowners, Penn State's stormwater advice also lists pervious pavers that can look like an ordinary brick or stone patio or driveway, set on a thick stone base, and suggests a professional landscaper for them. Its other options, such as redirecting downspouts to lawns and gardens and installing rain gardens, can also help a property manage its own water.

Whether a permeable surface counts differently under your ordinance is a question for the municipality.

What else comes with new paving?

Digging. Pennsylvania 811 asks for notice three to ten business days before excavation, and the contractor makes the call. Also think about where the water off the new surface will go: Penn State Extension notes that runoff erodes and washes out residential driveways and can pond and freeze.

For the concrete itself, see concrete driveways, patios and salt, and for the wider permit picture, what Pennsylvania requires. Contractors are on the masonry contractors page.

Sources

1. What is an MS4?, Penn State Extension
2. Roadside Guide to Clean Water: Porous and Permeable Paving Materials, Penn State Extension
3. How Can I Control Stormwater on My Property?, Penn State Extension
4. Is Stormwater Damaging My Property?, Penn State Extension
5. Stormwater Management, Article I: General Provisions, Township of Upper Darby
6. Get a Building Permit, City of Philadelphia
7. 34 Pa. Code § 403.62. Permit requirements and exemptions., Commonwealth of Pennsylvania (Pennsylvania Code)
8. How Much Does a Concrete Patio Cost? [2026 Data], Angi
9. Homeowners, Pennsylvania One Call System (Pennsylvania 811)
10. How Much Does a Concrete Driveway Cost in 2026?, Angi