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, Hopewell Township in York County takes permit applications at its Municipal Office, 3336 Bridgeview Road, Stewartstown; its Building Permits and Zoning page says the Township "uses two third party companies in order to process building permits and for enforcement of ordinances" and sends questions "on permits containing the requirement of the Universal Code Construction (UCC), or to schedule UCC inspections" to Dependable Construction Code Services, LLC, whose own site names Hopewell Township among municipalities contracted with it "as a third party inspection agency for all code disciplines of both non-residential and residential plan review and inspections." Section 5-103 of the Township Code adopts the code "by reference as the Building Code of the Township" and changes nothing in the code's roofing provisions, and Section 5-106 says that as the code adopts "new or updated versions" of its codes, "such codes automatically shall be updated as part of this Part"; neither the code nor the Township's pages name an edition.
Permit process
No Hopewell Township text read for this record says whether a residential reroof needs a building permit. Part 1 of Chapter 5 of the Township Code, the Hopewell Township Building Code (Ord. 2004-6, as amended), elects to administer the code and adopts it "by reference as the Building Code of the Township," adding only uncovered decks and a 1981 rule on roof drain seepage pits for stormwater; Section 5-106 repeals the Township's 1981 Building Permit Ordinance for permits issued after the Part took effect. It has no permit clause of its own for house repairs or alterations and names no reroofing. The Building Permits and Zoning page lists "Permits are required for the following" (sheds, pools, additions, wells, driveways, decks, patios and sun-rooms, interior remodeling, garages, fences, home occupations, signs, solar panels and generators) and names no roof work. The Township's Building/Zoning Permit Application says "This application is for ALL proposed projects in Hopewell Township" and names no roof work, Dependable's UCC Residential 2026 Fee Schedule posted by the Township has no roofing line (its only roof words are "Solar Panels (Ground and Roof Mounted)"), and Dependable's residents page says "Not sure if a permit is required, give us a call for an office meeting or onsite meeting" and names no roof work either way. 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." Section 5-110 sets a fine "of not more than $1,000 plus costs" for a violation of the Part, and the permits page asks for a "$150.00 non-refundable application/deposit fee for residential" permits and gives "15 Business days" as the expected turnaround. The Municipal Office (717-993-2027) is open Monday, Tuesday, Thursday and Friday, 8AM to 4PM, and closed to the public on Wednesday; Dependable Construction Code Services is at 717-759-5906. Read for this answer: Part 1 of Chapter 5 of the Township Code, Uniform Construction Code, in full, and the Chapter 5 contents; 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 Permits and Zoning and Forms pages; its Building/Zoning Permit Application; its 2026 fee schedule; and Dependable's UCC Residential 2026 and 2026 Zoning fee schedules, home page and residents page.