Buy a commercial building and the default is to depreciate the whole thing over
39 years. Residential rental property runs over
27.5 years. But a building is not one asset. It is a structure plus a large amount of equipment, finishes, and site work that would qualify for much shorter recovery periods if anyone separated them out.
A cost segregation study does that separation, supported by engineering-based documentation. Typically:
- 5-year property — carpeting, decorative lighting, specialty electrical serving equipment rather than the building, and certain fixtures.
- 7-year property — some furniture, fixtures, and equipment categories.
- 15-year land improvements — paving, site lighting, landscaping, fencing, and drainage.
- Structure — the walls, roof, and framing stay on the long life. This is usually most of the basis, and it does not move.
Shifting basis into shorter classes accelerates deductions into the early years, which is where they are worth the most in present-value terms. On buildings with substantial site work or specialty systems, studies commonly reclassify a meaningful share of depreciable basis — enough that the study pays for itself several times over in year one.
The risk side, which most pitches leave out
- Depreciation recapture. Accelerated deductions on personal property are recaptured as ordinary income on sale, not capital gain. Cost segregation is largely a timing benefit and a rate-arbitrage play — it is not free money, and if you sell soon after, some of it reverses.
- Passive activity limits. If the property is a passive activity to you, the accelerated loss may be suspended rather than usable now. An owner without material participation or real estate professional status can generate a large deduction and get no current benefit from it.
- Study quality. An engineering-based study with proper documentation holds up. A spreadsheet allocation from a vendor promising a percentage does not. We will tell you when a study is not worth commissioning.