New construction owners who default to 39-year straight-line depreciation are deferring deductions that IRS rules already allow them to take faster. Cost segregation for new construction is the strategy that corrects that, and it works better here than on any other property type.
Most owners never capture it. That means a $5 million commercial building typically has $1.4 to $1.75 million in components that qualify for 5-year, 7-year, or 15-year depreciation rather than 39-year treatment.
The sections below cover how cost segregation applies specifically to ground-up builds, why timing and documentation matter more here than anywhere else, what the OBBB bonus depreciation rules mean for projects underway now, and how to structure the study process from the earliest stages of a project.
- ●Reclassify components from 39-year into 5, 7, and 15-year schedules: Generating significantly larger deductions in the earliest years of ownership.
- ●Highest reclassification rates of any property type (28-35%): Purpose-built systems are clearly categorized as personal property and land improvements, and complete cost documentation is available from day one.
- ●Pre-construction engagement is the highest-value entry point: Engaging before or during construction allows real-time cost tracking, reduces estimation error at study time, and positions the owner for maximum first-year deductions in the placed-in-service year.
- ●100% bonus depreciation restored for qualifying new construction: The One Big Beautiful Bill permanently restored the rate for property placed in service after January 19, 2025. Projects where physical work began before January 20, 2025, qualify under prior TCJA-era rates (40% in 2025, 20% in 2026).
- ●Free preliminary analysis confirms ROI before any commitment: Most commercial new builds above $1,000,000 in cost basis generate study returns of 10:1 or better.
The Role of Cost Segregation for New Construction
The standard IRS treatment of a new commercial building is a single 39-year straight-line depreciation schedule. A $5 million building generates roughly $128,000 in annual deductions for 39 years. A cost segregation study separates the flooring, electrical systems, site work, and purpose-built infrastructure from the structural shell, placing each in its correct depreciation class under the Modified Accelerated Cost Recovery System (MACRS).
The table below illustrates the depreciation difference on a $3 million new commercial build, assuming 30 percent reclassification and 100 percent bonus depreciation for eligible components.
New construction is the single best opportunity for a cost segregation study because cost records are complete, accurate, and available from the project’s start.
There is no prior depreciation to recapture, no incomplete records to reconstruct, and no ambiguity about acquisition basis.
The standard depreciation problem for new builds
Straight-line depreciation over 39 years treats the entire building as a single asset with a uniform useful life. In practice, the building contains components with very different actual useful lives: flooring wears out in 5 to 10 years, parking surfaces in 15, while the structural walls and foundation may stand for 50 years or more.
MACRS recognizes this difference and provides shorter recovery periods for shorter-lived assets.
Cost segregation is the engineering process that identifies and documents those components so they can be depreciated on their correct schedules. The MACRS depreciation system is codified in IRS Publication 946.
How reclassification works in practice
A qualified engineer reviews the construction budget, architectural drawings, and contractor pay applications, then classifies each component to its correct MACRS asset class based on its function and relationship to the building structure.
On a $5 million new commercial building where 30 percent of the depreciable basis ($1.5 million) qualifies for 5-year and 15-year treatment, that $1.5 million is eligible for 100 percent bonus depreciation in the placed-in-service year under current law.
At a 37 percent marginal rate, that is $555,000 in additional first-year federal tax savings compared to straight-line depreciation on the same basis.
How new construction differs from existing property purchases
The table below shows how new construction compares to existing building acquisitions and renovation projects across the factors that most affect study outcomes:
New construction produces the most accurate studies because every cost is documented in real time and has never been depreciated before.
Existing building studies must work with whatever records are available and account for prior depreciation taken by the previous owner.
Cost Segregation Benefits for New Construction
New construction offers four structural advantages over other property types for cost segregation purposes. Each one directly affects the accuracy, completeness, and financial value of the study.
Higher reclassification rates vs. existing buildings
New commercial builds consistently reclassify 28 to 35 percent of depreciable basis into 5-year and 15-year asset classes, compared to 22 to 28 percent for existing building acquisitions.
The reason is simple: new construction contains purpose-built systems installed for a specific operational use. Dedicated electrical circuits for equipment, specialized HVAC for server rooms, custom flooring installed for an industrial use case, and security infrastructure designed for a specific tenant are all components whose function clearly distinguishes them from the structural shell.
Older buildings with mixed renovation histories make these distinctions harder to trace.
Documentation advantages of ground-up construction
New construction generates exactly what the IRS’s preferred study methodology requires:
- ●Contractor pay applications itemized by trade
- ●Architectural drawings that map systems to physical locations
- ●Construction contracts that separate labor from materials
- ●Change orders that capture scope adjustments in real-time
The IRS Cost Segregation Audit Technique Guide identifies the detailed engineering approach from actual cost records as the most accurate and most defensible study methodology. New construction is the only scenario in which that documentation set exists in complete, contemporaneous form.
That documentation advantage erodes over time. Records get lost, contractors close, and memories of original cost allocation become less reliable. Commissioning a study in the construction year, or during construction, captures the documentation at its most complete.
Pre-construction planning to maximize deductions
Engaging a cost segregation specialist before breaking ground is the highest-value entry point for most new construction projects.
Pre-construction engagement allows the project team to set up a cost-tracking framework aligned with MACRS asset classes, capturing costs as they occur rather than reconstructing them from memory after completion.
It also creates an opportunity to review design specifications with depreciation classification in mind, identifying where material or system choices affect reclassification without changing the building’s function.
A ground-up construction cost segregation engagement during the build phase produces the most accurate final study and positions the owner for maximum first-year deductions in the placed-in-service year.
OBBB bonus depreciation and new construction timing
The One Big Beautiful Bill, signed July 4, 2025, permanently restored 100 percent bonus depreciation for qualifying assets. The timing rules for new construction are specific and worth understanding precisely.
For a new construction project to qualify for 100 percent bonus depreciation, physical work on the project must have begun on or after January 20, 2025. Projects that started construction before that date qualify under the prior TCJA-era rates: 40 percent for 2025 and 20 percent for 2026.
The practical implication: a developer who broke ground on a new warehouse in March 2025 qualifies for 100 percent bonus depreciation on all 5-year and 15-year components identified in a cost segregation study. A developer who broke ground in November 2024 qualifies at the 40 percent rate for 2025.
For projects near the commencement threshold, a 10 percent safe harbor provision may apply. Verify the specific qualifying date with a tax advisor familiar with the OBBB rules before drawing any conclusions about your project’s eligibility.
Assets in New Construction That Qualify for Accelerated Depreciation
Classification is based on function, not appearance.
Cost segregation building components that directly serve a specific operational use, rather than the building’s general structural function, qualify for a shorter depreciation life under MACRS.
Five-year and 7-year personal property
Personal property is the highest-value reclassification category in most new construction studies.
Qualifying five-year and seven-year assets in a typical commercial new build include:
- ●Dedicated electrical systems wired to specific equipment or operational functions
- ●Specialty flooring installed for a particular use (rubber, epoxy, or hardwood in non-structural applications)
- ●Decorative and task lighting on dedicated circuits separate from general building lighting
- ●Built-in casework and cabinetry not serving a structural purpose
- ●Computer and data cabling infrastructure
- ●Security and surveillance systems
- ●Manufacturing equipment pads and anchor systems
These assets qualify as tangible personal property because they serve a specific use rather than the structural building envelope, and they could be removed or replaced without affecting the building’s structural integrity.
Fifteen-year land improvements
Land improvements cover site work outside the building footprint. New construction creates the full inventory of those improvements at once, making this a particularly productive category.
Qualifying 15-year assets typically include:
- ●Parking lot construction and paving
- ●Access roads and drives
- ●Exterior site lighting
- ●Perimeter fencing and security gates
- ●Sidewalks and pedestrian pathways
- ●Storm drainage systems
- ●Landscaping and irrigation systems
- ●Utility connections located outside the building footprint
Land itself is not depreciable and must be excluded from the depreciable basis before the study begins. Only the improvements made to the land qualify, and new construction provides the complete cost basis for those improvements from the project’s construction budget.
Qualified improvement property and new builds
QIP covers interior improvements to nonresidential buildings placed in service after the building’s original placed-in-service date. Because new construction is the original placed-in-service event, improvements made during construction do not qualify as qualified improvement property.
The distinction matters for planning purposes. For new construction, the reclassification opportunity lies in personal property and land improvements identified through cost segregation.
QIP opportunities arise later, when post-completion renovations are made to the original structure. A tenant improvement project completed two years after the building is placed in service would create a QIP opportunity at that point, not at the original construction stage.
What to Expect From the Cost Segregation Process for New Construction
Seneca Cost Segregation is an engineering firm that helps real estate investors and business owners accelerate depreciation and reduce taxable income through IRS-compliant cost segregation studies.
Our cost segregation study for new construction follows four stages. The process differs from an existing building study primarily in the timing and documentation steps:
Step 1: Pre-construction engagement and feasibility review
For new construction, engagement can begin before ground is broken or at any point during the build. Earlier is better, but studies can also be commissioned after completion.
The feasibility review covers projected construction costs, property type, and anticipated component mix to confirm that the study’s ROI justifies the fee before any commitment. Most commercial new builds above $1,000,000 in cost basis generate study returns that more than justify the engagement. A qualified firm provides this analysis at no cost.
Step 2: Cost tracking and documentation collection
For studies engaged during construction, we set up a cost-tracking framework that captures costs by component category as they are generated by the project.
For post-completion studies, we require the following documents from the owner: architectural drawings, construction contracts, subcontractor pay applications, change orders, and the final cost breakdown by trade. The quality and completeness of this documentation directly affect the study’s accuracy and the total reclassifiable basis identified.
Retaining contractor invoices, change orders, and subcontractor pay applications throughout the construction period is the single most important action a new construction owner can take to protect the value of a future cost segregation study.
Step 3: Engineering study and asset classification
Our engineer then reviews all documentation, conducts a site inspection (virtual or on-site), and classifies each component into its correct MACRS asset class based on its function, removability, and relationship to the building structure.
The methodology standard is the detailed engineering approach from actual cost records, as defined in the IRS Cost Segregation Audit Technique Guide. At the end of the study, we deliver a detailed engineering report and fixed asset schedule formatted for the CPA’s use on the tax return.
Step 4: CPA implementation and report delivery
The CPA uses the fixed asset schedule to set up depreciation on the tax return, applying the current bonus depreciation rate to the reclassified 5-year, 7-year, and 15-year assets identified in the study.
For qualifying new construction placed in service after January 19, 2025, that means 100 percent of the reclassified component cost is expensed in Year 1. For earlier projects, the applicable TCJA-era rate applies. The study report includes the documentation and methodology rationale needed to support the positions at filing and defend them under any subsequent IRS examination.
With over 10,200 studies completed and a money-back audit defense guarantee, we deliver results you and your CPA can count on. Contact Seneca to stop overpaying on taxes and start putting that money back into your portfolio.
How to Choose the Right Cost Segregation Firm for Your Project
Selecting a cost segregation firm for a new construction project involves different considerations than selecting one for an existing building purchase. Construction-specific process knowledge matters as much as general methodology quality.
When is cost segregation worth it? For new commercial construction costing more than $1,000,000, the study economics are almost always favorable. The question is which firm will produce the most accurate and defensible study for your specific project.
In-house engineering vs. outsourced methodology
Firms with engineers on staff deliver new construction studies with faster turnaround, direct accountability, and no markup from a third-party subcontractor.
In-house engineers can also coordinate directly with the construction team during the build phase, reviewing pay applications as they are generated rather than reconstructing costs from memory after completion.
Firms that subcontract technical work introduce a layer of coordination that adds time and reduces accountability. Ask any provider directly: are the engineers who prepare your studies on your payroll, or do you use outside contractors?
Track record with new construction studies
New construction studies require familiarity with contractor pay applications, construction budgets organized by trade, and the process of identifying component costs from a project’s detailed cost breakdown structure. This is distinct knowledge from what is needed to conduct a lookback study on an existing property.
Ask any firm how many new construction studies they have completed and whether they can walk through a sample report. Firms with genuine experience in this area can describe the process in specific, practical terms.
Audit defense and study guarantees
Two protections are worth requiring as written commitments before signing: lifetime audit defense at no additional charge, and a money-back or fee-refund guarantee if the study contains a material issue.
The cost of a cost segregation study for commercial new construction typically ranges from $5,000 to $30,000, depending on property size and complexity.
At the standard 10:1 ROI benchmark, a $10,000 study on a qualifying new build should generate $100,000 or more in first-year accelerated deductions net of the study fee. When that math holds, the study is worth pursuing. When it does not, a reputable firm tells you before you engage.
Common Mistakes With Cost Segregation for New Construction
These are the errors that consistently reduce total savings or create audit exposure for new construction owners:
The risk of engaging after construction closes
Waiting until the project is complete does not disqualify a property from a cost segregation study, but it does reduce accuracy.
Post-completion studies rely on reconstructed cost data rather than contemporaneous records. When contractor pay applications are missing, trade-level cost breakdowns are unavailable, or the original construction budget is summarized rather than itemized, the engineer must use the IRS’s less-preferred estimation methods to fill in gaps.
Those methods introduce variability that reduces both accuracy and defensibility.
The correct approach: engage a cost segregation specialist before or during construction. If that window has passed, retain every document from the build that is still available before commissioning a post-completion study.
Incomplete construction records and missed deductions
Construction budgets that lump materials and labor together without trade-level breakdowns are the most common documentation problem in new construction cost segregation work.
A general line item for “mechanical, electrical, and plumbing” at $1.2 million is far less useful than separate breakdowns showing electrical rough-in at $380,000, HVAC systems at $520,000, and plumbing at $300,000.
That level of detail allows the engineer to identify which portions of each trade qualify as personal property rather than structural components, and to support each classification with traceable cost documentation.
Retain contractor invoices, change orders, subcontractor pay applications, and construction progress documentation throughout the project. These records feed directly into the engineering study, and their absence at study time is the most common cause of missed deductions on new construction projects.
The OBBB commencement date and why it matters
Two otherwise identical new construction projects can carry significantly different bonus depreciation rates based solely on when physical work began.
A project where the first physical work occurred on or after January 20, 2025, qualifies for 100 percent bonus depreciation on all 5-year and 15-year components identified in a cost segregation study. A project where construction started before January 20, 2025, qualifies for 40 percent in 2025 and 20 percent in 2026 under the prior TCJA-era schedule.
The difference in first-year tax savings on a $5 million qualifying project with $1.5 million in reclassified components is approximately $370,000 in additional deductions (the delta between 100% and 40% bonus depreciation at a 37% tax rate).
For projects near the commencement date threshold, the 10 percent safe harbor provision may expand eligibility. Verify the specific qualifying date with a tax advisor before assuming which rate applies to your project.
Frequently Asked Questions
Property owners and developers building for the first time often have questions about eligibility, timing, and what happens to cost segregation deductions further down the road:
Conclusion
New construction is the highest-ROI scenario for cost segregation because documentation is complete, reclassification rates are highest, and with 100 percent bonus depreciation permanently restored for qualifying property placed in service after January 19, 2025, current-year deductions are as large as they have ever been under federal law.
The placed-in-service date is the critical timing anchor. A study commissioned in the year the building is placed in service captures the maximum first-year benefit. Waiting costs deductions that cannot be recovered at full present value.
Seneca Cost Segregation’s veteran-owned engineering team has helped property owners across all 50 states legally reduce their tax burden for over 12 years. On average, clients capture $171,243 in first-year deductions alone. That money goes back to work in their portfolio.
Most owners do not realize how much their property qualifies for until they ask. Request a free proposal and get a clear answer.
