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, Coolspring Township's Building Code Inspectors page lists three third-party inspection agencies with their building permit forms, and each form carries the Township's number, 724-475-2010; one agency's building permit application says the agency "has been hired as the Building Code Official by the municipality." The Township office is at 852 North Perry Highway, Mercer (724-475-2010), and its Zoning Officer takes zoning permit applications. The Township's Ordinances page, read October 12, 2026, lists ten ordinances and an ATV ordinance, none of them an ordinance adopting the Uniform Construction Code or a building permit ordinance, so no Township building ordinance was read for this record. Its Zoning Ordinance (Ordinance No. 89, amended December 2023) says in Section 1002.01 "A zoning permit shall be required for any of the following (except where otherwise indicated in this ordinance)" and lists "Construction, erection, enlargement, reconstruction, demolition, or structural alteration of any building, structure, and/or sign including placement of a mobile home on a property," and defines "Construction" as "The act or process of constructing, reconstruction, renovation, repair, extension, expansion, alteration, or relocation of a building or structure, including the placement of mobile homes." The ordinance has no roofing provision. This record does not decide whether a house reroof is "Construction" under that section, a zoning permit matter. The Township's pages name no residential code edition.
Permit process
Coolspring Township's pages do not say whether a house reroof needs a permit. The Township's pages, read October 12, 2026, say nothing on roofing. Its 2026 fee schedule (transcribed from the scanned page) lists "ZONING PERMIT" at $25 and "BUILDING PERMIT" at $25 and no roofing line, and the zoning permit application, the notice of building form, and the three agency permit applications (read from the rendered pages) name no roofing permit type. The Township's Ordinances page, read October 12, 2026, lists ten ordinances and an ATV ordinance, none of them an ordinance adopting the Uniform Construction Code or a building permit ordinance, so no Township building ordinance was read for this record. Its Zoning Ordinance (Ordinance No. 89, amended December 2023) says in Section 1002.01 "A zoning permit shall be required for any of the following (except where otherwise indicated in this ordinance)" and lists "Construction, erection, enlargement, reconstruction, demolition, or structural alteration of any building, structure, and/or sign including placement of a mobile home on a property," and defines "Construction" as "The act or process of constructing, reconstruction, renovation, repair, extension, expansion, alteration, or relocation of a building or structure, including the placement of mobile homes." The ordinance has no roofing provision. This record does not decide whether a house reroof is "Construction" under that section, a zoning permit matter. 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 house reroof needs a permit; ask the Township office (724-475-2010) before starting. Read for this answer: the Township's home, Ordinances, Applications, Building Code Inspectors, Information and Contact pages; its Zoning Ordinance in full; its 2026 fee schedule; its zoning permit application and notice of building form; and the three agency building permit applications it posts.