For most sheds, the honest answer is "it depends on which town you're in," which is a less satisfying answer than a flat yes or no, but it's the accurate one, and understanding why makes the actual phone call to your municipality much shorter.
The state exemption, and why it doesn't end the conversation
Pennsylvania's Uniform Construction Code exempts detached sheds, carports, and similar "utility and miscellaneous" structures under 1,000 square feet from the state's building permit requirement. That's a real exemption, not a myth, but two things narrow it considerably in practice.
First, state law also gives individual municipalities the authority to require a permit for these structures anyway, through their own local ordinance, and plenty of Delaware County municipalities have done exactly that. Some set their own threshold well below the state's 1,000-square-foot mark, sometimes as low as 100 to 200 square feet. There's no way to know your specific town's number without asking, since it isn't standardized across the county.
Second, even a shed that's fully exempt from the building permit under both state and local rules usually still needs a zoning permit. Zoning doesn't care about square footage exemptions for construction standards, it cares about where the structure sits: how far from the property line, whether it counts against your lot's impervious coverage limit, whether accessory structures are capped at a certain size or number in your district. A 10-by-12 shed with zero building code involvement can still get flagged for sitting too close to a side yard.
Why the exemption exists in the first place
The building-permit exemption isn't an oversight, it's a deliberate choice to keep small, low-risk accessory structures out of the same inspection process as a house addition or a garage. A prefab shed sitting on skids or a simple gravel pad doesn't carry the same structural stakes as something attached to your home's electrical or plumbing systems. That's also why the exemption disappears the moment a shed stops being simple: run electrical service to it, plumb it, or build it large enough to function as habitable or commercial space, and it's back under full Uniform Construction Code review regardless of square footage.
What changes once a shed needs a permit
If your municipality does require a permit, whether because of its size or because the local ordinance sets a lower bar than the state, the process generally looks at:
Foundation and anchoring, especially for anything larger than a small prefab kit, to confirm it won't shift or become a wind hazard.
Setback distance from property lines and, in some municipalities, from your own house, septic system, or well if you have one.
Electrical work, if you're running power to it, which needs its own separate electrical permit and inspection no matter how small the structure is.
The practical path
Measure the shed you're planning, footprint and height, before you call. Ask your municipality two specific questions: is a building permit required at this size, and is a zoning permit required regardless of size. Many code enforcement offices can answer both in one call, since the same office often handles both functions in smaller municipalities. Get the answer in writing or note who you spoke with and when, since "the person I talked to said it was fine" carries very little weight if a neighbor complains six months later or the shed becomes an issue when the property sells.
More
Find your municipality's permit and zoning contacts. See also the permit FAQ, the glossary, and Do You Need a Permit to Build a Deck in Delaware County, PA?.