Adopted building code
The 2021 International Residential Code, as adopted by the State in the Pennsylvania Uniform Construction Code (UCC). 34 Pa. Code 403.21(a)(7) adopts "The 'International Residential Code of 2021,' except that:" followed by the State's list of exclusions and modifications, effective January 1, 2026 (55 Pa.B. 7701). None of the State's changes touches Chapter 9, Roof Assemblies, or Section R803, Roof Sheathing, so those apply as the International Code Council publishes them. Work on existing buildings is also pointed to the State's existing-building code: "The repair, alteration, change of occupancy, addition and relocation of existing buildings must comply with Chapter 34 of the 'International Building Code of 2021' or with the 'International Existing Building Code of 2021'" (34 Pa. Code 403.21(f)). The UCC is the minimum everywhere in the state: "no municipality may propose or enact any ordinance which is less than the minimum requirement of the Uniform Construction Code" (Pennsylvania Construction Code Act, Act 45 of 1999, section 503(b)). The Act also lists work it "shall not apply to", including "Alterations to residential buildings which do not make structural changes or changes to means of egress" or to "Repairs to residential buildings," in each case "except as might be required by ordinances" kept in force under section 303(b)(1) or adopted under section 503 (Act 45 section 104(b)(5) and (6); 34 Pa. Code 403.1(b)(8) and (9)). The Act defines a repair as "The reconstruction or renewal of any part of an existing building for the purpose of its maintenance." So whether the code's roofing rules reach a given house reroof depends on the municipality's own ordinances. Everything above is Pennsylvania state law, the same in every municipality. Locally, Pennsbury Township, in Chester County, issues building permits through its own Building, Codes and Zoning Department at the Township office, 702 Baltimore Pike, Chadds Ford. Section 78-1 of the Township Code says "Pennsbury Township hereby elects to administer and enforce the provisions of the Pennsylvania Construction Code Act," and the Department's page says "Our team reviews and issues building permits, conducts inspections, enforces zoning ordinances, and ensures compliance with building and safety codes." Chapter 78 of the Township Code, Article I (Ord. No. 2004-3), read in full, adopts the Uniform Construction Code "as amended from time to time" as the Township's building code and names no roof work; Section 78-5A keeps in force building code ordinances adopted "on or before July 1, 1999," which "equal or exceed the requirements of the code," and this record found none naming roof work. Article II of the same chapter adopts a property maintenance code. No Township page read names a code edition.
Permit process
Pennsbury Township's code and pages read for this record do not say whether a house reroof needs a permit. Chapter 78 of the Township Code, Article I (Ord. No. 2004-3), read in full, adopts the Uniform Construction Code "as amended from time to time" as the Township's building code and names no roof work; Section 78-5A keeps in force building code ordinances adopted "on or before July 1, 1999," which "equal or exceed the requirements of the code," and this record found none naming roof work. Article II of the same chapter adopts a property maintenance code. The Township's Permit Application Instructions page says "Before beginning any work, verify whether your project requires a permit" and lists as "Common projects requiring permits" "New building construction, additions, interior and exterior alterations" and "Demolition or structural modifications"; it names no roof work. The Township's fee schedule resolution (effective January 2, 2024, posted as the current fee schedule) names no roof work; it prices residential alterations at "$75.00 for first $1,000.00 of construction cost plus $8.00 for each additional $1,000.00 or fraction thereof." Under state law, Act 45 section 104(b)(5) and (6) list "Alterations to residential buildings which do not make structural changes or changes to means of egress" and "Repairs to residential buildings" among work the Act does not apply to, "except as might be required by ordinances in effect pursuant to section 303(b)(1) or adopted pursuant to section 503," and 34 Pa. Code 403.62(c) says "A permit is not required for the exceptions listed in § 403.1(b) (relating to scope) and the following, if the work does not violate a law or ordinance." This record does not state whether the Township requires a permit for a house reroof; the instructions page says "Contact the Codes and Zoning Office or review the local zoning ordinance to confirm requirements before applying." The Department's phone is 610-388-1790; Township office hours are "Monday–Thursday, 8:30 am–1:30 pm" and the Code Enforcement Officer's are "Monday & Wednesday, 8:30 am–1:30 pm." Applications are taken in person at the Codes and Zoning Department office, and the fee schedule lists a "$1500.00 fine for commencing work without a permit." Read for this answer: Chapter 78 of the Township Code in full; every page of a search of the whole Township Code for "roof", "reroofing" and "re-roofing", which found no permit provision naming roof work; the Township's Building, Codes and Zoning Department, Permit Application Instructions and Forms and Applications pages; its fee schedule resolution; and its residential building permit and zoning permit applications.