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, Mohnton Borough administers the code itself: Section 5-101 of its Code (Ord. 678, June 9, 2004) says the Borough "hereby elects to administer and enforce the provisions of the Pennsylvania Construction Code Act," Section 5-102 adopts the Uniform Construction Code "as the municipal building code of the Borough of Mohnton," and Section 5-103 lets the governing body choose by resolution among an employee, "one or more construction code officials or third-party agencies" and other arrangements. The Borough's Permits page says "Applications will be forwarded to our Codes engineer (Great Valley Consultants), for processing," lists that firm at 75 Commerce Drive, Wyomissing (610 375-8822), and posts the Borough's residential building permit application; Borough Hall is at 21 North O'Neil Street (610-775-0660). The Borough's pages name no code edition for the reroofing provisions; the residential permit packet's sprinkler instruction cites "2009 IRC" for sprinkler design, Section 5-102 adopts the code "as amended from time to time," and this record has not read any 2009 edition's text and does not decide which edition the Borough applies.
Permit process
Mohnton Borough's own pages and code name no roof work as permit work or as exempt. Its Permits page (read October 10, 2026) sets a "$50 non-refundable application fee" for residential use and lists applications for building, fence, shed, pool, deck, demolition and other permits, with no list of work needing or not needing a permit and no roofing line. The Borough's 2024 fee schedule lists residential building permit fees for new dwellings, additions, "Alterations, renovations, or modifications" and miscellaneous structures and names no roof work, and its residential building permit application packet asks for "Roof materials and roof slope" on the elevation plans of new construction. Section 27-1101 of the zoning chapter says "No building, structure, or sign shall be erected, constructed, assembled, extended, reconstructed, replaced, demolished, converted, moved, added to or structurally altered" without "a permit therefor issued by the Zoning Officer"; it names no roof work, and this record does not decide whether a house reroof is a building or structure "reconstructed" or "replaced" under it. 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." Ask the Borough office (610-775-0660) or the codes engineer (610 375-8822) before starting. Read for this answer: Chapter 5, Code Enforcement, Part 1, Uniform Construction Code (Sections 5-101 to 5-107), and Part 2, Property Maintenance (Sections 5-201 and 5-202), in full; Chapter 4, Buildings (Part 2, Vacant Property); Chapter 11, Housing; Section 27-1101 of the zoning chapter and the Part 11 headings; every page of a search of the whole Borough Code for "roof" (9 results, none naming a permit) and for "reroofing" (none); the Borough's Permits, Ordinances, Departments and Contact pages; the residential building permit application packet, the zoning application and the 2024 fee schedule.