Structural Components: What the IRS ATG Says Belongs to a Building

The term “structural component” can be misleading in cost segregation because it does not refer only to beams, columns, foundations, and other components that physically hold a building up. Under the classification framework discussed in the IRS Cost Segregation Audit Technique Guide, structural components can include walls, floors, ceilings, windows, doors, HVAC, plumbing, electrical wiring, lighting, stairs, elevators, sprinkler systems, and other components related to the operation or maintenance of a building. That makes structural-component analysis one of the most important dividing lines between § 1245 property and § 1250 property. For CostSegRx engineers, the key question is not simply whether an asset looks structural. The analysis asks how the component is installed, how it relates to the building, what it serves, and what the property facts show.

Wondering how much tax you could save with cost segregation? Let’s find out. Schedule a Cost Segregation Strategy Call today.

Key Takeaways

• Structural components include more than load-bearing parts of a building.
• Building operation, integration, attachment, and function help drive the analysis.
• Correctly identifying structural components is central to § 1245 vs § 1250 classification.
• Electrical, HVAC, plumbing, roofs, stairs, elevators, and other systems provide useful examples.
• Construction documents and field conditions help support structural-component conclusions.
• A component-by-component example shows why contractor categories cannot determine classification.
• A structural component is defined by its relationship to the building, not simply by whether it carries a structural load.

What Is a Structural Component in Cost Segregation?

Treasury Regulation § 1.48-1(e)(2), as summarized in the ATG, provides a broad list of building structural components. The list includes walls, partitions, floors, ceilings and permanent coverings, windows, doors, central air-conditioning and heating systems, plumbing and plumbing fixtures, electrical wiring and lighting fixtures, chimneys, stairs, escalators, elevators, sprinkler systems, fire escapes, and other components relating to the operation or maintenance of a building.

That definition immediately corrects a common misunderstanding.

A component does not have to carry the weight of the building to be a structural component for this classification analysis.

An elevator is a useful example. The ATG's auto-manufacturing guidance treats permanently affixed elevators and escalators designed to remain in place as § 1250 property because they relate to the operation or maintenance of the building and are structural components. The description includes guide rails, cabs, doors, controls, escalator handrails, and related components.

A lighting system can also be a structural component. So can plumbing. So can HVAC.

The classification concept is therefore broader than structural engineering terminology.

For cost segregation, the important question is the component's relationship to the building.

How Is a Structural Component Determined?

The ATG makes clear that there is no universal bright-line test for separating § 1245 property from § 1250 property. Each situation can be factually intensive. It explains that determining whether property is a structural component can involve what constitutes an inherently permanent structure, how permanently an asset is attached, and whether it relates to the operation or maintenance of the structure.

Those questions require the engineer to look beyond a construction label.

Suppose an electrical contractor installs several systems in the same building. One portion supplies general lighting, receptacles, HVAC, and other building loads. Another portion serves specific machinery.

The fact that both systems appear under an electrical contractor's scope does not mean they automatically receive the same classification.

The ATG discusses the importance of ultimate use in its electrical case-law analysis. In Scott Paper Co. v. Commissioner, electrical power used for lighting, heating, ventilation, air conditioning, and other overall building operation was distinguished from electrical power serving production machinery.

That illustrates the CostSegRx principle that MEP system classification depends on function, not merely on the construction trade responsible for installing the system.

Why Do Structural Components Matter to § 1245 vs § 1250 Classification?

Structural components matter because they sit directly on the dividing line between tangible personal property and building-related real property.

The ATG explains that tangible personal property excludes land, buildings, inherently permanent structures, and their structural components. At the same time, tangible personal property can include other property contained in or attached to a building, such as machinery, office equipment, refrigerators, display racks, shelves, and signs.

So attachment to the building does not answer the question by itself.

A machine can be attached and still fall outside the structural-component category. A system that does not carry structural loads can still be a structural component because it serves the operation or maintenance of the building.

This is one reason CostSegRx emphasizes engineering asset classification rather than classifications based solely on asset names.

The engineer needs to establish what the component actually does.

That distinction becomes particularly important for integrated systems. General HVAC typically serves the building. Specialized environmental equipment installed solely because another process or machine requires controlled conditions can raise a different issue under the applicable rules. The ATG itself describes an example involving air-conditioning and humidification installed in a textile plant because the production process required a narrow temperature or humidity range.

The physical equipment may look similar.

Its relationship to the building and business activity may be very different.

What Are Examples of Structural Components in Commercial Property?

The ATG provides numerous examples that show how broad the structural-component concept can be.

A roof is an especially useful example. The ATG's industry guidance says roof components can include joists, rafters, decks, shingles, vapor barriers, skylights, trusses, girders, flashings, gutters, and drains. It also explains that decorative roof elements may qualify as structural building components based on their integration with the roof, not their load-bearing capacity. If removing the decorative element would expose building components to weather or moisture damage, or if the element houses building wiring or lighting, it can be part of the overall roof system.

That example illustrates why the phrase “structural component” should not be interpreted literally as “load-bearing component.”

Stairs provide another clear example.

The ATG's auto-manufacturing guidance describes stairs and handrails leading between building floors or levels and related to building operation or maintenance as § 1250 property and 39-year nonresidential real property. But stairs designed and constructed only to access, inspect, repair, or operate specific machinery or equipment are identified separately as § 1245 property.

Security systems provide another function-based comparison. In the ATG's manufacturing guidance, security systems protecting the building, contents, and occupants are treated as building-related § 1250 property. Systems used to track and monitor tangible inventory are treated separately as § 1245 property.

The equipment may include similar cameras, wiring, controls, and monitoring technology.

The function changes the analysis.

How Do Engineers Document Structural-Component Classification?

Documentation helps turn a classification opinion into a supportable engineering conclusion.

The ATG tells examiners to consider contemporaneous records such as permits, design studies, contractor payment records, AIA G702 and G703 documents, contracts, purchase orders, invoices, and other records that verify asset costs, descriptions, and functional use. It also notes that estimated allocations between § 1245 and § 1250 property, particularly for electrical and plumbing systems, may require an engineer experienced in construction and construction estimating.

A field inspection can add another layer of information.

The ATG explains that inspecting an asset as installed can reveal its purpose, use, installation, and construction.

That closely aligns with the CostSegRx engineering approach. Our engineers may use drawings, photographs, equipment schedules, specifications, invoices, contractor records, field observations, and owner interviews to establish what exists and what each component supports.

This is also why cost segregation audit readiness depends on more than having a depreciation schedule.

The supporting engineering story matters.

An engineer should be able to explain why a component was classified separately from the building or why it remained a building structural component.

How Can Structural-Component Analysis Affect Cost Allocation?

Illustrative example only. Figures shown are estimated for demonstrative purposes only. Actual land allocations, asset classifications, depreciation, and tax results depend on the specific property, supporting documentation, engineering analysis, and taxpayer circumstances.

Assume a manufacturing facility has $400,000 of construction costs recorded under mechanical, electrical, access, and architectural scopes.

Those contractor categories do not tell us how the entire $400,000 should be depreciated.

Suppose the engineering review identifies general building HVAC, electrical distribution serving lighting and receptacles, stairs connecting normal building levels, and roof components integrated into the building envelope.

Those facts may support treatment as building structural components and, in a typical commercial building, 39-year nonresidential real property.

Now suppose the same records also identify separate electrical connections serving qualifying manufacturing equipment and access stairs designed only to reach a particular machine.

Those assets raise different classification questions.

The engineering analysis therefore does not begin by assigning a percentage of the $400,000 to 5-year property or 39-year nonresidential real property.

It begins by determining what each portion of the $400,000 actually purchased.

This reflects the CostSegRx principle that contractors build, but engineers classify.

What Is the Most Important Structural-Component Principle?

The most important principle is that a structural component is not defined simply by whether it physically supports the building.

The ATG's framework includes walls, finishes, windows, HVAC, plumbing, electrical systems, lighting, stairs, elevators, sprinkler systems, and other components associated with building operation or maintenance. Its industry examples repeatedly demonstrate that function, integration, installation, and relationship to the building can distinguish otherwise similar components.

That is why CostSegRx engineers do not stop at a construction description.

They ask what the asset supports, how it is installed, how it interacts with the building, and what documentation supports that conclusion.

Some components properly remain part of 39-year nonresidential real property or 27.5-year residential rental property. Other assets can qualify for separate treatment when the applicable facts and classification framework support it.

The objective is not to separate everything possible from the building.

The objective is to understand where the building ends and the separately classified assets begin.

A structural component is defined by its relationship to the building, not simply by whether it holds the building up.