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, Washington Township administers the code through a third-party agency it retains: Section 145-1 of the Township Code says "Washington Township hereby elects to administer and enforce the provisions of the Pennsylvania Construction Code, Act 45 of 1999," and the Township's own page says Commonwealth Code Inspection Service, Inc. (CCIS), 1102 Sheller Ave., Chambersburg, "has been contracted by the Township to review plans and specifications for building projects," issue construction permits and enforce building code violations, while the Township issues land use permits from its office at 11798 Buchanan Trail East, Waynesboro. Section 145-2 adopts the Uniform Construction Code, "as amended from time to time," as the Municipal Building Code of Washington Township, and Section 145-6 A repeals all building code ordinances the Township adopted before it. Chapter 145 of the Township Code adopts the Uniform Construction Code "as amended from time to time" and names no edition, and the Township's pages name none. Chapter 145 changes nothing in the code's roofing provisions.
Permit process
Washington Township's code and pages do not say whether a house reroof needs a permit. Section 145-6 C of the Township Code says "When any building or construction activity is contemplated within the Township, application shall first be made to the Township at the Township offices on a form to be provided by the Township for the issuance of a land use permit," and that the land use permit "shall be a prerequisite to making application for a construction permit"; Section 360-120 A of the zoning chapter says "A land use permit must be obtained from the Township before any construction or development is undertaken within any district," and Section 360-120 C says "If a construction permit is required for a building project under the UCC," the applicant obtains it from the UCC Code Administrator after the land use permit. None of these names roof work, and this record does not decide whether a house reroof is "building or construction activity" or "construction or development" under them. The Township's Land Use Permit application is for a permit "to build, erect, or remodel a structure" and names no roof work except a "Roof materials" line in its part for new dwellings and additions; the CCIS building permit application the Township posts names no roof work; and the Township's 2026 fee schedule (Resolution No. 852) prices land use permits by the value of the improvement and has no roofing line. The Township's pages say "Your starting point is at the Township office by submitting a Land Use permit application" and "If you have any questions on the building permit and inspection process contact the Township Code Enforcement Officer (717-762-3128) or CCIS (717-262-0081)." 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 a permit is required for a house reroof in Washington Township; ask the Township office at 717-762-3128 and CCIS at 717-262-0081 before starting. Section 145-5 makes a violation of Chapter 145 a summary offense punishable by "a fine of not more than $1,000, plus costs of prosecution." The Township's page says CCIS keeps office hours at the Township building "every Tuesday and Thursday from 11:00 am until 1:00 pm"; the Township office is open 8:00 am to 4:30 pm, Monday through Friday. Read for this answer: Chapter 145 of the Township Code, Construction Codes, Uniform (Sections 145-1 to 145-9), in full; Article XIX of the zoning chapter, Administration and Enforcement, and Section 360-139; every page of a search of the whole Township Code for "roof" and for "reroofing," which found no permit provision naming roof work; the Township's Building, Code, Inspection & Zoning, Building Inspections and CCIS pages; its Land Use Permit application; the CCIS building permit application it posts; and its 2026 fee schedule, Resolution No. 852, including the CCIS residential fee page attached to it.