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, Valley Township in Chester County administers the Uniform Construction Code itself, through a third-party agency: Section 5-703 of the Township Code says "Valley Township hereby elects to and so shall administer and enforce the provisions of the Pennsylvania Construction Code Act," and the Township's Code Enforcement page names Building Inspection Underwriters, Inc. as its Codes/Building Inspector. Building permit applications go to the Township's Codes Department at 1145 West Lincoln Highway, Coatesville, and the page says "Permits are issued by appointment after a plan review has been completed." Section 5-701 adopts "the Uniform Construction Code as set forth in 34 Pa. Code, Chapters 401 through 405" as the official Municipal Building Code of Valley Township. Section 5-702 fills in Table R301.2(1) with design criteria including "Ice Shield Underlayment Required" "Yes", ground snow load 30 pounds and wind speed 90 mph. Section 5-702 of the Township Code (Ord. No. 2016-01) amends "Section R301 of the International Residential Code for One- and Two-Family Dwellings (2009)" and Section 5-701 says the code "shall be amended automatically by all amendments, supplements, additions and later editions," while the Township's page says only "Valley Township utilizes the PA UCC Building Code" and names no edition; this record has not read the 2009 edition's text and does not decide which edition the Township applies.
Permit process
Valley Township's code and pages read for this record do not say whether a house reroof needs a permit. Part 7 of Chapter 5 of the Township Code, the Township's Uniform Construction Code ordinance (Ord. No. 2004-04, read October 9, 2026), names no roof work either way and adds no permit clause of its own for house repairs. Its Section 5-706 keeps in force "All building code ordinances or portions thereof enacted by Valley Township prior to 11:59 p.m. prevailing time, Thursday, July 1, 1999" that equal or exceed the Uniform Construction Code, and Part 4 of the same chapter still adopts the "BOCA National Building Code, Twelfth Edition, 1993" (Ord. 94-1) as the Building Code of the Township; this record has not read that code's permit sections and does not decide whether or how Part 4 applies to a house today. The Township's fee schedule (Resolution No. 2025-01) prices "Roof Work (Structural)" at $150, a fee for the structural case only, and prices "Alterations and Repairs which do NOT increase area" generally. The Township's Code Enforcement page says nothing on roofing. It says "Building/Zoning permits are needed for, but not limited to: additions, decks, patios, pools, sheds, fences, garages and driveways," and "Prior to starting any project, call the Codes Department to find out what permits are required." 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 the Township requires a permit for a house reroof; ask the Codes Department (610-384-5751, extension 401) before starting. Section 5-708 sets a fine "of not less than $150 nor more than $1,000, per violation" of the Township's Uniform Construction Code ordinance, and the building permit application says two sets of plans and specifications must accompany it, with a non-refundable residential application fee of $75. The Administration and Codes Office is open Monday through Friday, 8:00 a.m. to 4:00 p.m. Read for this answer: Chapter 5 of the Township Code, Code Enforcement (Sections 5-101 to 5-710), in full, including Part 4 (BOCA National Building Code) and Part 7 (Uniform Construction Code); 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 Code Enforcement and Forms & Documents pages; and its building permit application and 2025 fee schedule, scanned documents read from their page images.