Inside a Cost Segregation Study: How a Building Becomes a Tax Shield for Its Limited Partners

There is often a person whose job is to walk through a brand-new $50 million apartment complex on the day after it closes and decide whether the parking-lot lights are 5-year property or 15-year property. They will go through each unit and tag the cabinetry, the carpet, the appliances, the closet shelving. They will measure the parking lot. They will look at the landscaping plan. They will photograph the HVAC equipment. Then they will sit down with the architectural drawings and the closing documents and produce a several-hundred-page report that translates the building, line by line, into the categories the U.S. tax code recognizes.

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This person is a cost segregation engineer. The work they do, in a building most LPs in the deal will never visit, can be one of the larger drivers of those LPs' after-tax returns.

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A cost segregation study is one of the most important pieces of value-creation work that happens after a private real estate transaction closes. For most accredited investors, it is also one of the least visible. This is a key workstream that drives the potential tax benefits of private real estate investments, one of the big selling points of the asset class. What follows is a deep dive on cost segregation study mechanics, the math on a hypothetical example investment, and what an LP sees on the Schedule K-1 as a result. A companion spreadsheet walks through a simplified, hypothetical example.

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How a Cost Segregation Study Works

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The U.S. tax code says that a residential rental building gets depreciated over 27.5 years and a commercial building over 39 years. Those are long, slow schedules. They are also, on inspection, a fiction. A building is not one thing. It is a structural shell plus a great many components with much shorter useful lives. Carpet wears out in seven to ten years. Appliances in five to ten. Landscaping plantings die. Parking-lot asphalt cracks and gets resurfaced. Specialty HVAC components are rebuilt or replaced on cycles measured in single-digit years.

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The IRS has acknowledged this since long before the modern tax code. The agency permits, and has refined over time, a methodology called cost segregation: a study performed by qualified engineers and tax professionals that reclassifies the components of a building according to their actual recovery periods under Section 168. The 27.5- or 39-year shell stays in its long bucket. But the components with shorter useful lives get moved out, into 5-, 7-, and 15-year categories, where they can be depreciated much faster — and, under current law, expensed entirely in the first year via bonus depreciation under Section 168(k), as we will discuss.

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The framework governing how this is done is laid out in the IRS Cost Segregation Audit Technique Guide. A defensible study is engineering-based, not estimation-based. There is real methodology here, and there can be a real audit risk for sponsors who cut corners.

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Building Components a Cost Segregation Study Reclassifies

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The list of items a cost seg engineer pulls out of the 27.5- or 39-year bucket and into the shorter recovery classes is longer than most LPs realize. A short and not-quite-exhaustive version, as of this writing:

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5-year property (personal property used in the rental activity):

• Appliances (refrigerators, ovens, dishwashers, in-unit laundry)
• Carpet and other floor coverings that are not adhered to the structure
• Window treatments, blinds
• Cabinetry and millwork that is not integral to the structure
• Specialty kitchen and bath fixtures that are removable

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7-year property:

• Office and clubhouse furniture
• Fitness-center equipment
• Certain decorative lighting and removable fixtures

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15-year property (qualified improvement property and land improvements):

• Parking lots, sidewalks, curbing, drive aisles
• Landscaping, irrigation, fencing
• Site lighting, parking-lot lighting poles
• Signage
• Pool and spa improvements
• Site utilities outside the building footprint

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What stays in the 27.5- or 39-year bucket is the structural shell of the building itself: walls, roof, foundation, framing, structural plumbing and electrical inside the walls, and structural HVAC trunks.

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On a well-built modern multifamily property, a typical engineering-based cost segregation study will reclassify anywhere from 15% to 30% of the depreciable basis into the shorter recovery classes. On industrial property the percentage can be higher. The exact figures are always asset-specific.

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A Hypothetical Example: Cost Segregation on a $50 Million Multifamily Asset

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The companion spreadsheet to this article (download here) walks through an illustrative cost segregation study on a $50 million multifamily asset, with $10 million of land allocation and $40 million of depreciable basis. The numbers there are illustrative, not tied to a specific Lightstone DIRECT offering, but the proportions are typical for institutional multifamily.

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The headline result is consistent across most assets at this scale:

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• A $50 million property with a $40 million depreciable basis generates roughly $1.45 million in year-one depreciation under straight-line treatment alone.
• The same property with a cost segregation study and 100% bonus depreciation generates roughly $11.09 million in year-one depreciation — about eight times the straight-line figure.
• The trade-off is in later years. Years two through ten see slightly less depreciation than the straight-line schedule would have produced, because all of the 5-, 7-, and 15-year property was already fully expensed in year one.
• Over a 10-year window, the cumulative depreciation under cost segregation is roughly $20.9 million versus $14.5 million under straight-line — a difference of about $6.4 million pulled forward into year one. The full $40 million eventually gets depreciated either way. The difference is timing.

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The reason timing matters as much as it does is the time value of money. A dollar of depreciation taken now, at top marginal rates, is worth meaningfully more than the same dollar taken twenty years from now. This can amount to meaningful post-tax income that can be reinvested in the near term rather than fairly far into the future. For a high-income LP using passive losses to shelter passive income, the timing advantage compounds.

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Tangible Benefits of a Cost Segregation Study for Accredited Investors

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An LP with a $250,000 position in the transaction, allocated their share of depreciation pro rata, could see something like the following on the Schedule K-1 that arrives in the spring of year two:

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• A meaningful paper loss in box 2 of the K-1 (rental real estate loss).
• A K-1 footnote breaking down the depreciation between regular and bonus depreciation components.
• Potentially additional state K-1s for the state where the property is located, depending on jurisdiction.

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In the illustrative example in the companion spreadsheet, that $250,000 position generates a year-one paper loss of roughly $111,000 with cost segregation in place, versus about $15,000 under straight-line alone. The cash distribution from the deal in year one looks, for tax purposes, like a loss rather than income.

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K-1s in years two through four typically show smaller paper losses, because the bonus depreciation kicker is exhausted and a portion of the building's basis is still being depreciated on the 27.5-year schedule. Passive activity loss rules under Section 469 apply. Passive losses can shelter passive income but generally not earned income. Most accredited investors are not real estate professionals under the Section 469(c)(7) definition and should not attempt to claim that status without a competent CPA's blessing.

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In other words, this paper loss cannot shelter your W2 income. However, if you have income from other private real estate investments, for example, you may be able to shelter that income.

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Again, these statements do not constitute tax advice – consult with a qualified tax professional when considering these concepts or the tax implications of real estate investment in general.

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Who Performs Cost Segregation Studies, What They Cost, and When

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Who runs cost segregation studies? The defensible studies are engineering-based and performed by qualified firms — sometimes specialized cost segregation engineering firms, sometimes the cost-seg practice of a Big-Four or regional CPA firm. The IRS Audit Technique Guide describes what an adequate study looks like; "rule-of-thumb" or pure-CPA estimation studies are more likely to be challenged.

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What do they cost? A study on a single multifamily property typically runs $10,000 to $25,000 depending on size and complexity. On larger industrial assets the absolute number is higher; per dollar of basis it is typically lower. The present-value benefit of the accelerated deductions ordinarily exceeds the study cost by a wide margin.

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When in the deal lifecycle does the study get done? Usually in the first 12 months after closing, in time for the first year's tax return. Studies can also be performed retroactively on properties that have already been in service — "look-back" studies, which use a Section 481(a) catch-up adjustment to capture missed depreciation in a single year. A look-back can be a powerful tool for an LP whose existing sponsor never bothered with a study in the first place.

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Does every sponsor run them? This varies. At Lightstone DIRECT, we run a full cost segregation study, generally on every investment presented to individual LPs on the platform.

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Recapture, Audit Risk, and the Rate That Moves

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Depreciation is timing, not free money. When the property eventually sells, the accumulated depreciation gets recaptured. Section 1250 recapture on the real-property portion is taxed at federal rates of up to 25%; Section 1245 recapture on the personal-property portion (which includes most of what a cost segregation study reclassifies into 5- and 7-year buckets) is taxed at ordinary rates. The compounding value of cost segregation comes from holding the deferred tax for years, redeploying that capital, and using a 1031 exchange or a step-up in basis at death to convert deferral into elimination. For an investor with no 1031 plan, no estate-planning use case, and a short hold, the headline benefit is real but smaller than it looks.

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Studies can be challenged. The IRS does periodically audit cost segregation studies, particularly aggressive ones. The defense is a real engineering-based study with documented methodology. A 100-page report with photographs, drawings, and component-level analysis tends to settle these challenges quickly. A four-page spreadsheet from a non-engineer does not.

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Bonus depreciation rates change. The cost segregation study itself is permanent in practice — once a building's components are properly classified, they stay classified. But the first-year bonus depreciation rate applied to that classification is a function of legislation. It is currently 100% under the OBBBA. It was 40% as recently as January 2025. It will be whatever Congress says it is at any given future moment.

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The Question to Ask the Sponsor

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The engineer walking the building is doing something that meaningfully changes the after-tax math of the investment, on every deal, for every LP. The work happens quietly. It does not appear in the marketing deck. It is unlikely to be mentioned on the call.

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It is worth asking the sponsor about. Specifically: who performed the cost segregation study, when, and is the report available for your CPA to review? If the answer is unclear, you have learned something. If the answer is clean and specific — third-party engineering firm, full report on file, available on request — you have learned something else.

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Cost Segregation Studies – The Lightstone DIRECT Approach

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This is another place where Lightstone’s scale and vertical integration shows up to the potential benefit of Lightstone DIRECT LPs. Lightstone will generally conduct a thorough cost segregation study on each Lightstone DIRECT asset. These cost segregation studies are conducted by in-house, licensed tax professionals, working in concert with the company’s asset management personnel to fine-tune the approach to each asset.

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Lightstone pursues market-standard approaches to cost segregation study methodology. Again, these materials should be shared with a licensed CPA to determine the tax implications of any investment for any particular investor.

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Soren Godbersen is Chief Growth Officer at Lightstone DIRECT. This article is for informational purposes only and is not tax, legal, or investment advice. Tax outcomes depend on individual circumstances and on legislation that changes from year to year. Consult a qualified tax professional before acting on any of the above. Past performance does not guarantee future results; all investments carry risk.

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Further reading:

• IRS Cost Segregation Audit Technique Guide (Internal Revenue Service)
• Treasury and IRS guidance on bonus depreciation under the One Big Beautiful Bill Act, Notice 2026-11
• Internal Revenue Code Section 168 (depreciation), Section 168(k) (bonus depreciation), Section 1245 (personal property recapture), Section 1250 (real property recapture), Section 469 (passive activity loss rules), Section 481(a) (changes in accounting method, relevant to look-back studies).