Cost Segregation for Small Multifamily (5 to 20 Units): Component Breakdown and Year 1 Savings

Small multifamily buildings in the 5 to 20 unit range occupy an awkward spot in most investors' tax planning. They are large enough that straight-line depreciation leaves real money unclaimed, but small enough that owners assume a cost segregation study is not worth the fee. That assumption is usually wrong. A 12-unit building purchased for $1.6 million typically supports a study that produces $280,000 or more in additional first-year depreciation.

The reason has less to do with the building shell than with what surrounds it. Small multifamily properties carry a high ratio of site improvements to square footage, because parking, walkways, and landscaping serve a relatively small building footprint.

Where the Reclassified Basis Comes From

Residential rental property depreciates over 27.5 years under IRC Sec. 168(e)(2)(A). A study moves qualifying components out of that class and into shorter recovery periods defined by IRC Sec. 168(e)(3).

In the 5 to 20 unit range, five-year property under Sec. 168(e)(3)(B) typically runs 11% to 14% of depreciable basis. The largest contributors are unit appliance packages, which at 12 units means twelve refrigerators, ranges, dishwashers, and often in-unit laundry. Carpeting and vinyl plank flooring, window treatments, cabinetry that is not structurally integrated, decorative lighting, and dedicated electrical circuits serving appliances round out the class.

Fifteen-year land improvements under Sec. 168(e)(3)(C) generally run 10% to 14%, higher as a percentage than in large complexes. Surface parking, curbing, site lighting, perimeter fencing, mailbox structures, dumpster enclosures, retaining walls under four feet, irrigation, and landscaping all qualify. On a compact suburban twelve-plex, paved area frequently exceeds the building footprint.

Combined reclassification lands between 22% and 28% of depreciable basis for most properties in this size band.

A 12-Unit Worked Example

An investor buys a 12-unit building for $1,600,000. Land is allocated at $260,000, leaving a depreciable basis of $1,340,000. The study identifies five-year property of $174,200 (13%), fifteen-year land improvements of $160,800 (12%), and structural components of $1,005,000 (75%).

With 100% bonus depreciation under IRC Sec. 168(k), made permanent by the One Big Beautiful Bill Act, the $335,000 of reclassified property is fully deductible in year one. The remaining structure contributes roughly $36,545 of straight-line depreciation. Total first-year depreciation is approximately $371,545, against roughly $48,727 under a straight 27.5-year schedule.

The Constraint That Actually Matters

A $371,000 deduction on a building that generates $190,000 of gross rent creates a large paper loss. Whether that loss reduces your tax bill depends on IRC Sec. 469. Long-term rentals are passive by default, so the loss offsets other passive income and otherwise suspends and carries forward.

Three paths unlock it. Real estate professional status under Sec. 469(c)(7) makes rental activity non-passive if you meet the 750-hour and more-than-half tests and materially participate. The Sec. 469(i) allowance permits up to $25,000 of loss against ordinary income, but it phases out entirely at $150,000 of modified AGI, which excludes most buyers of $1.6 million buildings. Finally, the loss can offset passive income from other rentals or syndications. Our guide on deducting rental losses against W-2 income works through each path in detail.

Small Buildings and Study Economics

Study fees scale with square footage, not with the size of the deduction. A 12,000 square foot twelve-plex costs meaningfully less to study than a 90,000 square foot complex, while the percentage reclassified is often higher. Properties with a depreciable basis above $300,000 generally clear the ROI threshold comfortably.

One caution specific to this size band: many small multifamily buyers hold the property in a single-member LLC and self-manage. That is fine for the study, but it makes the material participation documentation more important, not less. Contemporaneous time logs matter when the deduction is this large relative to the property.

Buildings You Already Own

If you bought the building three years ago and never ran a study, you do not amend. Form 3115 under Rev. Proc. 2015-13 permits an automatic change in accounting method, and the entire cumulative missed depreciation is claimed as a Sec. 481(a) adjustment in the current year. A building held four years often produces a larger single-year deduction than a fresh acquisition, because four years of catch-up compress into one return. The Form 3115 playbook covers the filing mechanics.

Owners weighing this against a larger acquisition should also read our breakdown of cost segregation for apartment buildings generally, which compares outcomes across size bands.

Frequently Asked Questions

Is a 5-unit building large enough to justify a cost segregation study?

Usually yes, if the depreciable basis exceeds roughly $300,000. Study cost scales with square footage while the reclassification percentage in small multifamily is often higher than in large complexes, so the ratio of deduction to fee is frequently better on small properties than owners expect.

Does the 27.5-year residential classification hurt my cost segregation result?

It reduces the structural depreciation gap slightly compared to a 39-year commercial property, but it does not change the reclassified components. The five-year and fifteen-year property is identified the same way. Residential classification actually gives you faster depreciation on the remaining structure.

What percentage of a small apartment building can be reclassified?

Typically 22% to 28% of depreciable basis for buildings in the 5 to 20 unit range. Properties with large surface parking lots, extensive landscaping, or in-unit laundry tend toward the upper end. Buildings on tight urban lots with structured parking tend lower.

Can I take the deduction if I have a W-2 job?

Only if you qualify as a real estate professional under IRC Sec. 469(c)(7), have other passive income to absorb the loss, or fall under the modified AGI threshold for the Sec. 469(i) allowance. Otherwise the loss suspends and carries forward until you have passive income or sell the property.

How long does a small multifamily study take?

Most studies in this size range are delivered within two weeks of receiving the closing statement, appraisal, rent roll, and property photographs. New construction takes slightly longer when we work from contractor cost detail rather than reconstructing values.

---