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, Monaghan Township issues building permits from its own office at 202 South York Road, Dillsburg: its Building Permit Application and Permit says "Application is hereby made for a Building Permit in accordance with the requirements of the Uniform Construction Code and applicable amendments" and ends with an "Issued By" line, and its permit submission sheet says "Permit fees are based on the fee schedule resolution" and that "RAS ENGINEERING REVIEW AND INSPECTION FEES ARE ADDITIONAL." The Township's Ordinances page (read October 12, 2026) lists "UCC Building Ordinance" (June 14, 2004, "In Force") and an ordinance that "Provides for Building Permit Requirements, fee structure, etc., Remedies and Penalties for Violations thereof" (July 9, 2001, "In Force"), and the 1975 "Building Permit Ord. and Fees" as amended, but the page links no text for any of the three, so none was read for this record and this record does not decide whether any of them reaches a house reroof. The Township's pages name no edition of the International Residential Code, and the Township's Uniform Construction Code ordinance was not read; this record does not decide which edition the Township applies to a house.
Permit process
Monaghan Township's pages read for this record do not say whether a house reroof needs a permit. The Township's permit submission sheet separates "Residential Zoning Permits (including sheds and detached garages under 1,000 S.F., fences, paving of existing driveways, non-structural renovations of existing structures including finishing of basements)" from "Residential Building Permits (including all new dwellings or additions, renovations with structural changes, swimming pools or spas, accessory structures over 1,000 S.F.)," and neither list names roofing or reroofing. The sheet closes with "THIS IS ONLY TO BE USED AS A GUIDE. REVIEW THE ZONING ORDINANCE AND UCC PRIOR TO SUBMITTING AN APPLICATION." The Township's Ordinances page (read October 12, 2026) lists "UCC Building Ordinance" (June 14, 2004, "In Force") and an ordinance that "Provides for Building Permit Requirements, fee structure, etc., Remedies and Penalties for Violations thereof" (July 9, 2001, "In Force"), and the 1975 "Building Permit Ord. and Fees" as amended, but the page links no text for any of the three, so none was read for this record and this record does not decide whether any of them reaches a house reroof. 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." Monaghan Township issues building permits from its own office at 202 South York Road, Dillsburg: its Building Permit Application and Permit says "Application is hereby made for a Building Permit in accordance with the requirements of the Uniform Construction Code and applicable amendments" and ends with an "Issued By" line, and its permit submission sheet says "Permit fees are based on the fee schedule resolution" and that "RAS ENGINEERING REVIEW AND INSPECTION FEES ARE ADDITIONAL." The building permit fee is "$10.00 plus $2.00/thousand, or portion thereof, of construction value with a minimum of $100.00" plus a "Building Permit Administration Fee: $ 55.00." This record does not state whether the Township requires a permit for a house reroof; ask the Township office (717-697-2132) before starting. The office is open Monday to Thursday 8 am to 4 pm and Friday 8 am to 12 pm. Read for this answer: the Township's home, Forms & Applications and Ordinances pages; the Building Permit Application and Permit; the Zoning Permit Application; and the permit submission sheet in full. The Township's Zoning Ordinance PDF is a scanned image with no readable text and was not read, and the Township's codified ordinances are not online.