Roofing Historic Buildings in Pennsylvania: Preservation Standards and Challenges

Pennsylvania contains more than 165,000 properties listed on or eligible for the National Register of Historic Places, making it one of the most preservation-active states in the country. Roofing work on these structures intersects two distinct regulatory frameworks — building codes and historic preservation standards — creating compliance requirements that differ substantially from standard residential or commercial roofing. This page describes the regulatory landscape, material classification standards, professional qualification requirements, and common conflicts that arise when roofing historic structures in Pennsylvania.

• Definition and Scope
• Core Mechanics or Structure
• Causal Relationships or Drivers
• Classification Boundaries
• Tradeoffs and Tensions
• Common Misconceptions
• Checklist or Steps
• Reference Table or Matrix

Definition and Scope

Historic building roofing in Pennsylvania applies to structures that carry a formal designation — through the National Register of Historic Places, a Pennsylvania State Historic Preservation Office (SHPO) determination, or a locally designated historic district administered under a municipal historic commission. The scope extends to contributing buildings within certified historic districts even when an individual structure lacks a standalone listing.

The Pennsylvania State Historic Preservation Office, operating under the Pennsylvania Historical and Museum Commission (PHMC), serves as the primary state-level authority. Federal oversight applies when federal tax credits or federal funding are involved, in which case the National Park Service (NPS) Technical Preservation Services guidelines become binding (NPS Preservation Briefs).

Local historic commissions in cities such as Philadelphia, Pittsburgh, Lancaster, and Bethlehem add a third layer of review authority. Philadelphia's Philadelphia Historical Commission, for example, holds jurisdiction over more than 11,000 designated properties and requires a Certificate of Appropriateness before exterior roofing alterations on those structures may proceed.

Scope limitations apply here: this reference covers Pennsylvania-specific regulatory structures and does not address historic preservation law in neighboring states, federal Section 106 review processes as standalone topics, or the Internal Revenue Service tax credit application mechanics beyond their relevance to material standards. Properties outside Pennsylvania's jurisdiction — including federally owned structures subject solely to the Secretary of the Interior's Standards without PHMC involvement — fall outside the direct scope of this coverage. For a broader view of the state's roofing regulatory environment, see the regulatory context for Pennsylvania roofing.

Core Mechanics or Structure

The Secretary of the Interior's Standards for Rehabilitation, published by the National Park Service, form the foundational framework applied in Pennsylvania historic roofing reviews. The Standards identify four treatment approaches: Preservation, Rehabilitation, Restoration, and Reconstruction. Roofing projects most commonly fall under Rehabilitation or Preservation, each with distinct material replacement tolerances.

Under the Rehabilitation standard, original roofing materials must be retained and repaired where feasible. Replacement is permissible only when deterioration is documented as beyond repair. Replacement materials must match the historic material in visual character, including color, texture, and profile, as evaluated by the reviewing authority.

Pennsylvania's building code authority rests in the Pennsylvania Uniform Construction Code (UCC), administered by the Pennsylvania Department of Labor and Industry (PA Department of Labor and Industry). The UCC adopts the International Building Code (IBC) and International Residential Code (IRC) with state amendments. Where conflicts arise between the UCC's performance requirements and historic preservation material standards, Pennsylvania's UCC includes provisions under Chapter 34 of the IBC that allow alternative compliance pathways for existing historic buildings.

Permitting for historic roofing work in Pennsylvania requires both a building permit through the local code enforcement office and, separately, a Certificate of Appropriateness or equivalent approval from the relevant historic commission. These are parallel processes, not sequential, meaning neither automatically satisfies the other.

Causal Relationships or Drivers

Several structural factors drive the distinctive compliance requirements for historic roofing in Pennsylvania.

Material specificity of historic construction. Pennsylvania's historic building stock includes a high concentration of structures originally roofed in Welsh and Vermont slate, terne-coated metal, clay tile, wood shingles, and copper. Pennsylvania slate roofing is particularly prominent in buildings constructed between 1850 and 1940 in counties including Northampton, Lehigh, and Lancaster, where local quarrying operations provided material. These are not interchangeable with modern synthetic alternatives under preservation standards without specific documentation.

Federal Historic Tax Credit mechanics. The Federal Historic Tax Credit, providing a 20% credit on qualified rehabilitation expenditures under 26 U.S.C. § 47, requires NPS certification that the project meets the Secretary of the Interior's Standards. Pennsylvania supplements this with a state Historic Preservation Tax Credit program administered through PHMC and the Pennsylvania Department of Community and Economic Development (DCED). Both credit streams require that roofing material choices pass standards review, creating a financial incentive that directly governs contractor decisions.

Climate-driven deterioration rates. Pennsylvania's freeze-thaw cycles, which average 40 to 60 freeze-thaw events annually in central and eastern portions of the state, accelerate joint failure, flashing separation, and substrate rot in aged historic roofing assemblies. This creates recurring pressure to replace materials that preservation standards require be repaired rather than replaced. The Pennsylvania weather impact on roofing is a direct driver of the pace at which historic structures require intervention.

Classification Boundaries

Historic roofing projects in Pennsylvania fall into three primary regulatory tiers based on the nature and scope of designation:

Tier A — Federally listed / Tax credit projects: Structures listed on the National Register and seeking federal or state historic tax credits. NPS certification is required. Material substitution requires documented justification submitted to the State Historic Preservation Office.

Tier B — State or locally designated without active tax credits: Structures under PHMC determination or local historic commission jurisdiction. Certificate of Appropriateness required from the relevant local commission. NPS Standards are used as the interpretive framework but are not federally binding.

Tier C — Contributing structures in certified historic districts: Buildings that are not individually listed but contribute to a listed district's historic character. These structures carry the same Certificate of Appropriateness requirements as individually listed properties within the district's boundaries.

Buildings that are merely old — constructed before 1940, for example — but carry no formal designation fall under standard UCC requirements only. Age alone does not trigger preservation review.

Tradeoffs and Tensions

The central tension in Pennsylvania historic roofing is between preservation fidelity and modern performance standards. Authentic Welsh slate, for example, can achieve service lives exceeding 150 years but requires skilled installation labor that is increasingly scarce. The Pennsylvania roofing workforce and trades sector shows documented shortages in licensed slate and ornamental metal roofing specialists.

Synthetic slate products — fiber-cement, polymer composites — offer improved installation accessibility and Class A fire ratings under ASTM E108, but their approval by historic commissions varies by jurisdiction. Philadelphia's Historical Commission applies more restrictive interpretations than commissions in smaller municipalities, sometimes rejecting synthetic materials that SHPO has accepted in other counties.

Flashing materials present a parallel conflict. Historic copper and lead-coated copper flashing systems are compatible with original masonry substrates, but lead-coated copper faces restrictions under Pennsylvania environmental regulations because of lead content in stormwater runoff. Terne-coated stainless steel is the common substitute, but its visual character differs from historic terne metal in ways that preservation reviewers may evaluate differently depending on visibility from public rights-of-way.

Energy code compliance creates a third tension point. Pennsylvania's UCC energy provisions, which reference ASHRAE 90.1-2022, require minimum insulation values that can be difficult to achieve within historic roof profiles without raising the roofline or altering eave geometry — both alterations that preservation standards typically prohibit. Chapter 34 of the IBC provides variance pathways, but these require formal documentation and are not automatic.

Common Misconceptions

Misconception: A building must be "on the National Register" for preservation standards to apply.
Correction: Local historic commission designation triggers Certificate of Appropriateness requirements independently of any National Register listing. Philadelphia, Pittsburgh, and Lancaster all maintain locally designated properties not on the National Register that are fully subject to preservation review.

Misconception: Using a "period-appropriate" material automatically satisfies standards.
Correction: Material appropriateness is evaluated property-specifically based on the documented historic material of that structure, not on what was common in the period generally. Substituting cedar shingles for a building historically roofed in slate is not compliant simply because both predate 1900.

Misconception: Preservation approval replaces building permit requirements.
Correction: Certificate of Appropriateness and building permits are separate instruments issued by different authorities. Obtaining one does not waive or substitute for the other. Both are required for lawful completion of roofing work on designated historic structures in Pennsylvania.

Misconception: Synthetic roofing products are categorically prohibited on historic buildings.
Correction: The NPS Technical Preservation Services and Pennsylvania SHPO evaluate synthetic products on a case-by-case basis against criteria of visual character match, durability, and reversibility. Approval of specific products has occurred in documented instances where visual compatibility was demonstrated.

Checklist or Steps

The following sequence describes the standard procedural pathway for roofing a designated historic structure in Pennsylvania. This is a reference description of the process, not professional or legal guidance.

1. Confirm designation status — Verify whether the structure is individually listed, contributing to a historic district, or locally designated. Check PHMC's Pennsylvania Historic Resource Survey and the local municipal historic commission registry.
2. Identify all applicable review authorities — Determine whether federal tax credits are involved (triggering NPS review), whether PHMC review is required, and which local commission holds Certificate of Appropriateness authority.
3. Document existing conditions — Photograph and document existing roofing material, substrate, flashing, and drainage systems before any alteration. This documentation is required for tax credit applications and supports variance requests.
4. Conduct material analysis — Identify historic roofing material type, manufacturer if determinable, and original installation method. Laboratory analysis may be required for obscure historic alloys or composite materials.
5. Prepare a preservation methodology statement — Describe proposed repair or replacement scope, materials, and justification. This statement is submitted with Certificate of Appropriateness applications.
6. Submit Certificate of Appropriateness application — File with the relevant local historic commission or PHMC. Review timelines vary: Philadelphia's Historical Commission meets monthly; smaller commissions may operate quarterly.
7. Apply for building permit — Submit to the local code enforcement office under the Pennsylvania UCC. Include documentation of any Chapter 34 variance requests if applicable.
8. Engage qualified contractors — Roofing contractors working on designated historic structures should hold relevant specialty qualifications. Pennsylvania roofing contractor licensing requirements apply alongside any preservation-specific competency standards.
9. Conduct work per approved scope — Any deviation from the approved scope requires amended Certificate of Appropriateness approval before proceeding.
10. Final inspection and documentation — Complete inspections under the building permit and retain all photographs, material certifications, and inspection records. Tax credit projects require these records for NPS certification submission.

Reference Table or Matrix

For reference on how historic roofing intersects with the broader landscape of Pennsylvania roofing types and material options, the Pennsylvania historic building roofing topic area provides additional material classification detail, and an overview of the full sector is available at the Pennsylvania Roofing Authority index.

References

• National Park Service Technical Preservation Services — Preservation Briefs
• Secretary of the Interior's Standards for Rehabilitation (NPS)
• Pennsylvania Historical and Museum Commission (PHMC)
• Pennsylvania Department of Labor and Industry — Codes and Standards (UCC)
• Pennsylvania Department of Community and Economic Development — Historic Preservation Tax Credit
• Philadelphia Historical Commission
• National Register of Historic Places (National Park Service)
• International Building Code Chapter 34 — Existing Structures (ICC)
• 26 U.S.C. § 47 — Federal Historic Tax Credit (Cornell LII)