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, Lancaster Township administers the code itself: Section 126-1 of the Township Code says "Lancaster Township hereby elects to administer and enforce the provisions of the Pennsylvania Construction Code Act," and the Township's Planning & Zoning Department, whose director supervises "the Building Code inspector," takes building permit applications at its office, 1353 Meadowcreek Lane, Lancaster; "All inspections are arranged through the building inspector by calling (717) 859-3350." Section 126-2 adopts the Uniform Construction Code, "as amended from time to time," as the municipal building code, and Chapters 126 and 110 change nothing in the code's roofing provisions and name no code edition; the department's pages name none either. No ordinance reaching residential reroofing was found in the chapters read.
Permit process
Lancaster Township's code and permit pages do not say whether a house reroof needs a permit. The department's Building/Zoning Permit FAQs page (read October 7, 2026), under "When do I need a Building Permit?", says "Because there are so many variables, please email or call the township Planning and Zoning Department for information." Its Building/Zoning Permit Application (revised June 11, 2024) is "the base form for all construction, renovations, alterations, fences, decks, patios, and accessory structures in Lancaster Township" and names no roof work, and the Township's Schedule of Fees (Resolution No. 2022-07, adopted April 11, 2022) has no roofing line; it lists a PA UCC Building Permit Fee of $4.50 and says building permit inspection fees are "Assessed by inspector." Chapter 126 of the Township Code, Construction Codes, Uniform (Ord. No. 2010-08), and Chapter 110, Building Construction (Ord. No. 2010-07), each adopt the Uniform Construction Code by reference, "as amended from time to time," and neither names roof work nor adds a permit requirement of its own. Section 126-5 A keeps in force building code ordinances adopted on or before July 1, 1999 that equal or exceed the code; none is published with the chapter. Section 160-7 of the Township's floodplain management chapter says "A permit shall be required before any construction or development is undertaken within any area of Lancaster Township"; this record does not decide whether that floodplain permit 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." This record does not state whether the Township requires a permit for a house reroof; ask the Planning & Zoning Department at (223) 221-7515 before starting. Where a permit is needed, the application goes to the Planning/Zoning Office at 1353 Meadowcreek Lane with three sets of construction plans, a site plan, the total construction cost and insurance certificates; the department says a residential application takes ten to fifteen business days, and the permit fee is paid when the permit is approved. The Schedule of Fees sets a "Penalty for failure to obtain Building or Zoning Permit" of "Double the permit fee," and Section 126-7 sets a fine of "not more than $1,000 and costs of prosecution" for violating the chapter or the code. Read for this answer: Chapter 126 of the Township Code, Construction Codes, Uniform (Sections 126-1 to 126-10), and Chapter 110, Building Construction (Sections 110-1 to 110-12), in full; Chapter 204, Property Maintenance; Section 160-7 of the floodplain chapter; every page of a search of the whole Township Code for "roof" and for "reroofing," which found no permit provision naming roof work; the Planning & Zoning and Building/Zoning Permit FAQs pages; the Building/Zoning Permit Application; and the Schedule of Fees.