9.2 Historic Preservation, SHPO Reviews & Secretary of the Interior Standards

9.2 Historic Preservation, SHPO Reviews & Secretary of the Interior Standards

[!NOTE] Preservation Scope in Pre-Design & Site Analysis: Historic preservation intersects architectural programming and site analysis whenever a project site contains an existing historic structure, borders a designated historic district, or involves federal or state funding, permits, or land. Architects must determine whether a property is listed in or eligible for the National Register of Historic Places, navigate Section 106 statutory reviews with the State Historic Preservation Officer (SHPO), select the appropriate Secretary of the Interior treatment approach, and evaluate character-defining features before proposing building alterations, demolition, or new additions.

Historic buildings and cultural landscapes represent non-renewable architectural resources. Integrating historic structures into modern facility programming requires a rigorous understanding of preservation statutory frameworks, taxation incentives, and technical intervention standards. Siting a new building adjacent to a landmark, demolishing an existing facility, or executing an adaptive reuse conversion requires balancing contemporary life safety, accessibility, and programmatic goals with statutory historic preservation mandates.

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The National Historic Preservation Act (NHPA) of 1966 & Section 106

The foundation of American preservation policy is the National Historic Preservation Act (NHPA) of 1966 (codified in 54 U.S.C. 300101 et seq.). The NHPA established:

• The National Register of Historic Places (NRHP).
• The role of the State Historic Preservation Officer (SHPO) in every US state and territory.
• The Tribal Historic Preservation Officer (THPO) program on tribal lands.
• The Advisory Council on Historic Preservation (ACHP), an independent federal agency overseeing federal preservation compliance.
• The statutory Section 106 review process.

The Section 106 Review Process (36 CFR Part 800)

Section 106 mandates that federal agencies take into account the effects of their undertakings on historic properties and afford the ACHP a reasonable opportunity to comment prior to the approval of the expenditure of funds or the issuance of any license.

                                 ┌──────────────────────────────────┐
                                 │   Federal "Undertaking" Exists   │
                                 │  (Funds, Permits, Licenses, Land)│
                                 └────────────────┬─────────────────┘
                                                  │
                                                  ▼
                                 ┌──────────────────────────────────┐
                                 │ STEP 1: Initiate & Define APE    │
                                 │ (Area of Potential Effects)      │
                                 └────────────────┬─────────────────┘
                                                  │
                                                  ▼
                                 ┌──────────────────────────────────┐
                                 │ STEP 2: Identify Historic Props  │
                                 │ (Listed or Eligible for NRHP)    │
                                 └────────────────┬─────────────────┘
                                                  │
                                                  ▼
                                 ┌──────────────────────────────────┐
                                 │ STEP 3: Assess Adverse Effects   │
                                 │ (Criteria of Adverse Effect)     │
                                 └────────────────┬─────────────────┘
                                                  │
                         ┌────────────────────────┴────────────────────────┐
                         ▼                                                 ▼
         ┌──────────────────────────────┐                  ┌──────────────────────────────┐
         │     No Adverse Effect        │                  │        Adverse Effect        │
         │ Review Concludes with SHPO   │                  │ (Destruction, alteration,    │
         │ Concurrence Letter           │                  │  visual/audible intrusion)   │
         └──────────────────────────────┘                  └──────────────┬───────────────┘
                                                                          │
                                                                          ▼
                                                           ┌──────────────────────────────┐
                                                           │ STEP 4: Resolve Adverse Eff. │
                                                           │ Consultation leads to signed │
                                                           │ MEMORANDUM OF AGREEMENT (MOA)│
                                                           └──────────────────────────────┘

What Triggers Section 106?

A Section 106 review is triggered whenever a project involves a federal undertaking. An undertaking encompasses:

1. Direct construction or demolition by a federal agency (e.g., General Services Administration, Department of Veterans Affairs, Department of Defense).
2. Federal financial assistance, grants, or loan guarantees (e.g., Federal Highway Administration highway funds, HUD Community Development Block Grants, Federal Transit Administration grants, EPA Clean Water State Revolving Funds).
3. Federal permits, approvals, or licenses (e.g., a Clean Water Act Section 404 dredge-and-fill permit issued by the US Army Corps of Engineers, an FAA airspace obstruction permit, or a FERC pipeline approval).

The Four-Step Section 106 Process:

1. Initiate the Review & Define the Area of Potential Effects (APE): The federal agency (or its designated applicant/architect) defines the geographic boundary within which an undertaking may directly or indirectly cause alterations in the character or use of historic properties. The APE encompasses physical disturbance (excavation, construction limits) and indirect auditory, traffic, and visual viewshed impacts.
2. Identify Historic Properties: Conduct field surveys, archival research, and architectural evaluations to identify all properties within the APE that are listed in or formally eligible for listing in the National Register of Historic Places.
3. Assess Adverse Effects: In consultation with the SHPO/THPO, evaluate whether the undertaking will alter, directly or indirectly, any of the characteristics that qualify the property for inclusion in the National Register. Criteria of Adverse Effect include:
   • Physical destruction of or damage to all or part of the property.
   • Alteration of a property that is not consistent with the Secretary of the Interior's Standards.
   • Removal of the property from its historic location.
   • Change of the character of the property's use or of physical features within the setting that contribute to its historic significance.
   • Introduction of visual, atmospheric, or audible intrusions that diminish the integrity of the property's significant historic features.
   • Neglect of a property which causes its deterioration.
4. Resolve Adverse Effects: If an adverse effect is determined, the federal agency must consult with the SHPO, THPO, ACHP, local municipalities, and the public to develop and evaluate alternatives or mitigation measures. This consultation culminates in a legally binding Memorandum of Agreement (MOA) or Programmatic Agreement (PA). The MOA legally obligates the agency to execute agreed mitigation measures (such as Historic American Buildings Survey [HABS] / Historic American Engineering Record [HAER] architectural documentation, archaeological data recovery, redesign modifications, or historical interpretive markers) before work proceeds.

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National Register of Historic Places (NRHP) Criteria & Integrity

The National Register of Historic Places (NRHP), maintained by the National Park Service (NPS) under the Department of the Interior, is the official federal list of districts, sites, buildings, structures, and objects significant in American history, architecture, archaeology, engineering, and culture.

The 50-Year Rule & Criteria Consideration G

To be eligible for the National Register, a property must generally be at least 50 years old. This temporal threshold ensures that historians and architects can evaluate the property with objective historical distance rather than subjective contemporary enthusiasm.

• Criteria Consideration G (Exceptional Significance): A property achieving significance within the past 50 years may be eligible if it demonstrates exceptional historical, architectural, or cultural significance. Landmark examples evaluated under Consideration G include the Gateway Arch in St. Louis (Eero Saarinen), the Vietnam Veterans Memorial (Maya Lin), the Salk Institute (Louis Kahn), and key Cold War aerospace facilities.

The Four National Register Significance Criteria (36 CFR 60.4)

A property must be associated with an important historic context and satisfy at least one of four criteria:

+--------------------------------------------------------------------------------+
|                 National Register Criteria for Evaluation                      |
+--------------------------------------------------------------------------------+
| Criterion A: EVENTS       | Associated with events that made a significant     |
|                           | contribution to broad patterns of our history.     |
| Criterion B: PERSONS      | Associated with the lives of persons significant   |
|                           | in our past.                                       |
| Criterion C: ARCHITECTURE | Embodies distinctive characteristics of a type,    |
|              & DESIGN     | period, or method of construction; represents work |
|                           | of a master; possesses high artistic values.       |
| Criterion D: INFORMATION  | Has yielded, or may likely yield, information      |
|              POTENTIAL    | important in prehistory or history (archaeology).  |
+--------------------------------------------------------------------------------+

1. Criterion A (Events): Properties associated with events that have made a significant contribution to the broad patterns of national, state, or local history (e.g., labor union strikes, civil rights marches, canal/railroad construction corridors, military battles).
2. Criterion B (Persons): Properties associated with the lives of persons significant in our past (e.g., the home or laboratory of an inventor, statesman, or social reformer during the period of their major accomplishments).
3. Criterion C (Design / Construction / Architecture): The most frequently applied criterion in architecture. Properties that:
   • Embody distinctive characteristics of a type, period, or method of construction (e.g., an exemplary 1910 Craftsman bungalow, a 1930s Art Deco cinema, a heavy-timber textile mill).
   • Represent the work of a recognized master architect, engineer, or builder (e.g., Frank Lloyd Wright, Louis Sullivan, Julia Morgan).
   • Possess high artistic values.
   • Represent a significant and distinguishable entity whose components may lack individual distinction (a historic district).
4. Criterion D (Information Potential): Properties that have yielded, or may be likely to yield, information important in history or prehistory. Applied predominantly to terrestrial and submerged archaeological sites (e.g., Native American settlements, 18th-century kiln sites, shipwreck sites).

The Seven Aspects of Historic Integrity

Significance alone does not qualify a property for the National Register; the property must also retain historic integrity—the physical authenticity of a property's historic identity, evidenced by the survival of physical characteristics that existed during the property's period of significance. The NPS defines seven distinct aspects of integrity:

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The Secretary of the Interior's Standards for the Treatment of Historic Properties

Codified in 36 CFR Part 68, the Secretary of the Interior's Standards for the Treatment of Historic Properties provide statutory principles for evaluating work on historic buildings. The standards establish four distinct treatment approaches, arranged along a spectrum of physical intervention and historical retention:

PRESERVATION              REHABILITATION             RESTORATION              RECONSTRUCTION
(Least Intervention)   (Adaptive Reuse)         (Specific Period)       (New Construction)
     │                        │                       │                       │
     ▼                        ▼                       ▼                       ▼
Keep & repair existing   Alter & add for new     Remove later work;      Recreate vanished
materials from all       use; retain historic    recreate missing from   assets with new work
historical periods       character-defining      one period of           based on historical
without alterations      features                significance            documentation

1. Preservation

• Definition: Focuses on the maintenance, stabilization, and repair of existing historic materials and the retention of a property's form as it has evolved over time.
• Key Characteristic: Highest retention of existing fabric. Acknowledges that changes and alterations made to a building across different historical periods may have acquired significance in their own right. These later alterations are retained rather than stripped away.
• Application: Historic house museums, stable architectural landmarks where no programmatic changes or contemporary functional upgrades are required. No modern additions are permitted.

2. Rehabilitation (Most Critical for ARE 5.0 PA & Adaptive Reuse)

• Definition: Acknowledges the need to alter or add to a historic property to meet continuing or changing uses while preserving those portions or features that convey historical, cultural, or architectural values.
• Key Characteristic: The adaptive reuse standard. Permits the introduction of new mechanical/electrical/plumbing systems, modern life safety components (sprinklers, enclosed egress stairs), ADA accessibility ramps and elevators, and contemporary interior partitioning, provided character-defining exterior facades and primary public interior spaces are preserved.
• The 10 Standards for Rehabilitation (36 CFR 67.7):
  1. A property will be used as it was historically, or be given a new use that requires minimal change to its distinctive materials, features, spaces and spatial relationships.
  2. The historic character of a property will be retained and preserved. The removal of distinctive materials or alteration of features, spaces and spatial relationships that characterize a property will be avoided.
  3. Each property will be recognized as a physical record of its time, place and use. Changes that create a false sense of historical development, such as adding conjectural features or elements from other historic properties, will not be undertaken.
  4. Changes to a property that have acquired historic significance in their own right will be retained and preserved.
  5. Distinctive materials, features, finishes, and construction techniques or examples of craftsmanship that characterize a property will be preserved.
  6. Deteriorated historic features will be repaired rather than replaced. Where the severity of deterioration requires replacement of a distinctive feature, the new feature will match the old in design, color, texture, and, where possible, materials. Replacement of missing features will be substantiated by documentary and physical evidence.
  7. Chemical or physical treatments, if appropriate, will be undertaken using the gentlest means possible. Treatments that cause damage to historic materials will not be used.
  8. Archaeological resources will be protected and preserved in place. If such resources must be disturbed, mitigation measures will be undertaken.
  9. New additions, exterior alterations, or related new construction will not destroy historic materials, features, and spatial relationships that characterize the property. The new work will be differentiated from the old and will be compatible with the historic materials, features, size, scale and proportion, and massing to protect the integrity of the property and its environment.
  10. New additions and adjacent or related new construction will be undertaken in such a manner that, if removed in the future, the essential form and integrity of the historic property and its environment would be unimpaired.

3. Restoration

• Definition: Depicts a property at a particular period of time in its history (the "period of significance") by retaining or recreating features from that specific period and removing features from other periods.
• Key Characteristic: Requires extensive historical, physical, and archival evidence. Any elements, wings, or alterations added after the chosen restoration period are intentionally demolished and removed, while missing features from that target era are reconstructed.
• Application: Presidential birthplaces, battleground structures, or historic monuments restored to interpret a specific historical moment (e.g., restoring Monticello to Thomas Jefferson's 1809 configuration).

4. Reconstruction

• Definition: Re-creates vanished or non-surviving sites, landscape features, or structures in new construction.
• Key Characteristic: Executed entirely with contemporary new materials based on exhaustive historical, architectural, and archaeological research. Conjectural recreation without historical documentation is strictly prohibited.
• Application: Rebuilding long-demolished landmarks for historical education (e.g., the Governor's Palace at Colonial Williamsburg or historical military forts).

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The Federal 20% Historic Rehabilitation Tax Credit

The Federal Historic Preservation Tax Incentives program, established under Internal Revenue Code (IRC) Section 47 and co-administered by the National Park Service (NPS), the Internal Revenue Service (IRS), and state SHPOs, provides a substantial 20% federal income tax credit for private commercial investments in historic rehabilitation.

+--------------------------------------------------------------------------------+
|            Federal 20% Historic Tax Credit Eligibility Framework               |
+--------------------------------------------------------------------------------+
| 1. Certified Historic Structure   | Listed individually on National Register   |
|                                   | OR contributing structure in historic dist.|
| 2. Substantial Rehabilitation     | Qualified Rehab Expenditures (QREs) exceed |
|    Test                           | greater of $5,000 or adjusted basis in 24m.|
| 3. Income-Producing Asset         | Commercial, office, industrial, or rental  |
|                                   | residential (Owner-occupied DOES NOT QUAL).|
| 4. NPS Certified Rehabilitation   | All work fully complies with Secretary of  |
|                                   | the Interior's Standards for Rehabilitation|
+--------------------------------------------------------------------------------+

Mathematical Mechanics: The Substantial Rehabilitation Test

To qualify, the project's Qualified Rehabilitation Expenditures (QREs) must exceed the adjusted basis of the building (or $5,000, whichever is greater) within a 24-month measuring period (or a 60-month phased rehabilitation plan):

$\text{Adjusted Basis} = \text{Purchase Price} - \text{Land Value} - \text{Depreciation} + \text{Capital Improvements}$

$\text{Required QRE Threshold} > \text{Adjusted Basis of Building}$

Worked Calculation: A developer acquires a historic warehouse for $2,000,000. A certified property appraisal allocates $500,000 to the underlying land value and $1,500,000 to the building. The adjusted basis is:

$\text{Adjusted Basis} = \$2,000,000 - \$500,000 = \$1,500,000$

To qualify for the 20% tax credit, the developer must invest more than $1,500,000 in qualifying rehabilitation hard/soft costs within the 24-month window. If the developer spends $3,000,000 in QREs, the federal tax credit generated is:

$\text{Tax Credit} = \$3,000,000 \times 0.20 = \$600,000\text{ dollar-for-dollar tax credit}$

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Evaluating Character-Defining Features & Designing Compatible Additions

Character-Defining Features

Architects evaluating historic structures must identify the primary architectural elements that convey the building's historical and architectural significance:

• Exterior Facades: Primary street-facing facades possess the highest significance; secondary and rear alley facades have lower relative significance.
• Fenestration Patterns: Window-to-wall ratios, rhythm of openings, original double-hung or steel industrial sashes, muntin/mullion profiles, and historic glazing.
• Materials & Ornament: Hand-molded brick, terra cotta cornices, rusticated stone bases, decorative metal work, and lime mortar joints.
• Interior Spatial Volumes: Grand entrance vestibules, monumental marble stairs, double-height banking halls, exposed heavy timber roof trusses, or decorative plaster ceilings.

Designing Compatible New Additions (Standards 9 & 10)

When programmatic growth requires expanding a historic facility, the design of the new addition must adhere to two core principles:

1. Distinct Yet Compatible (Avoid False Historicism):

   • Differentiated: The new addition must not copy or replicate historic detailing exactly. Designing a new wing with faux-historic ornaments creates a counterfeit historical record, misleading the public regarding what is authentic historic fabric versus contemporary construction.
   • Compatible: The addition must respect the historic building's massing, height, scale, rhythm, directional orientation, and proportion of openings. Materials should be high-quality and sympathetic (e.g., contemporary glass, steel, terracotta, or smoothly dressed stone that harmonizes with historic brick without imitating its ornamental style).
   • Subordinate Placement: Additions should be located on secondary or rear elevations, set back from primary street facades, and kept lower in height than the historic roofline.

2. Reversibility (Standard 10):

   • New additions must be designed and constructed so that if they were to be removed in the future, the essential form and structural integrity of the historic building would remain unimpaired.
   • Connection points between old and new should be minimized, often utilizing a recessed glazed hyphen or light-touch structural link that cuts openings only into non-character-defining secondary walls or existing window bays rather than destroying primary load-bearing masonry facades.

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ARE Exam Traps & Common Preservation Oversights

• Trap: Believing National Register Listing Restricts Private Owners: Listing on the National Register of Historic Places does not restrict a private property owner from modifying, altering, or even demolishing their property using their own private capital! The National Register imposes restrictions only when federal or state funding, permits, or licenses are involved (Section 106). Local municipal historic district ordinances and local landmark commissions hold the only legal police power to stop private demolition.
• Trap: Abrasive Sandblasting on Historic Masonry: A frequent exam trap involves cleaning historic masonry with abrasive grit blasting or high-pressure water washing (> 400 psi). Sandblasting strips the hard, protective outer vitrified crust from historic fired brick, exposing the soft, porous interior core. Moisture rapidly penetrates the soft brick, causing catastrophic spalling and structural collapse during freeze-thaw cycles. Standards mandate the gentlest means possible (low-pressure water < 300 psi and mild non-ionic detergents).
• Trap: Repointing with Hard Portland Cement Mortar: Historic brickwork constructed prior to the 1930s utilized soft, flexible, vapor-permeable lime-sand mortar. Using modern hard Type S or Type M Portland cement mortar during repointing creates a mortar joint that is harder and less flexible than the brick itself. When the wall experiences thermal expansion and moisture migration, the rigid mortar transfers compressive stresses directly to the brick edges, shearing off the brick faces (spalling). Repointing mortar must always be softer and more vapor-permeable than the masonry units.
• Trap: Window Replacement Over Repair: Standard 6 mandates repairing deteriorated historic features whenever feasible. Specifying wholesale replacement of repairable original wood or steel windows with modern vinyl or anodized aluminum storefront assemblies will disqualify a project from SHPO approval and historic tax credits.