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, Oakmont Borough takes building permit applications at the Borough Office, 767 Fifth Street, Oakmont, and the Borough's Building and Zoning page says "Building Inspection Underwriters of PA, Inc. (BIU) issues all of our Permits" and "All building permits and inspections are completed by BIU." Section 82-1 of the Borough Code (Ord. No. O25-2004) says the Borough "hereby elects to administer and enforce the provisions of the Pennsylvania Construction Code Act." Section 82-2 adopts "The Uniform Construction Code, contained in 34 Pa. Code, Chapters 401-405, as amended from time to time" as the Building Code of the Borough, and Section 82-5A keeps Building Code ordinances adopted "on or before July 1, 1999" that equal or exceed the code in force. Section 82-2 adopts the Uniform Construction Code "as amended from time to time," Section 77-15 names the 2003 International Residential Code, and the Borough's pages name no edition; this record has not read the 2003 edition's text and does not decide which edition the Borough applies to a house.
Permit process
No Oakmont Borough office text read names reroofing as permit work or as exempt. Section 77-5 of the Borough Code (Ord. No. 041-2003) says "No building or other structure shall be erected, moved, extended, demolished or structurally altered without a building permit having been issued by the Building Inspector. A building permit shall not be required for minor repairs to existing buildings or structures, provided that no structural changes or modifications are involved." Section 77-15 (Ord. No. 042-2003) adopts the 2003 International Residential Code, whose permit sections are not published with the Borough Code and were not read for this record. In the Zoning chapter, Section 205-1601 says "A building permit is not necessary for exterior painting or the removal and replacement of lights or roofing shingles, siding, windows, doors, chimneys or entrances," with applications made "to the Zoning Officer." The Borough's building permit application lists "( ) Roofing - Total square feet" among its Type of work boxes (a scanned form, transcribed from the rendered page image), and the 2024 Schedule of Fees prices residential "Alterations & Repairs" at ".015 of total construction cost" with no roofing line. The Borough's Building and Zoning page and Frequently Asked Questions page say nothing on roof work. 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." The only Borough text read that names roof work is the Zoning chapter's building permit section, and the Borough's office pages neither require nor exempt a reroof in their own words, so this record does not decide whether an ordinary reroof needs a permit from the Borough's code agency. Ask BIU at 412-766-2565 before work starts. Section 77-14 sets a penalty of "not less than $50 nor more than $1,000" for each offense under the Building Permit Ordinance. Completed applications go to the Borough Office, where BIU picks them up; once BIU approves a permit it is returned to the Borough Office, which contacts the applicant for pick-up and cost, and inspections are scheduled with BIU. The Borough Office, 412-828-3232, is open Monday through Friday, 8:30 a.m. to 4:30 p.m. Read for this answer: Chapter 82 of the Borough Code (Construction Codes, Uniform, Sections 82-1 to 82-7) and Chapter 77 (Building Construction, Sections 77-1 to 77-16) in full; Article XVI of the Zoning chapter (Sections 205-1601 to 205-1605); every page of a search of the whole Borough Code for "roof" and for "reroofing"; the Building and Zoning, Forms and Frequently Asked Questions pages; the building permit application; and the 2024 Schedule of Fees.