Key Takeaways
- Your depreciable basis is the lower of adjusted basis or fair market value at conversion—not the current market value
- Cost segregation applies the same way it does for any rental; the only difference is how you calculate the starting basis
- If your home appreciated before conversion, that appreciation does not increase your depreciable basis
- A cost seg study on a converted residence can still produce $15,000–$60,000+ in Year 1 tax savings depending on the property
Converting a primary residence into a rental property is one of the most common ways investors enter the landlord world. You move out, you rent it out, and suddenly you have a depreciable asset. But the depreciation rules for a converted residence are different from a property you purchased as an investment from day one—and those differences affect how cost segregation works.
The confusion usually starts with one question: what is my depreciable basis? The answer is straightforward once you know the rule, but it trips up investors and even some tax preparers. This article breaks down the IRS basis rules for converted residences, explains how cost segregation applies, and covers the scenarios where a study does and doesn't make financial sense.
The Basis Rule: Lower of Adjusted Basis or FMV
When you convert a personal residence to a rental property, the IRS does not let you depreciate the current market value. Under Reg. 1.168(i)-4 and the principles in IRS Publication 527, your depreciable basis for the converted property is the lower of:
This rule matters because most homeowners have experienced appreciation. If you bought a home for $350,000 in 2018 and it's worth $550,000 when you convert it in 2026, your depreciable basis starts at $350,000 (plus any capital improvements you've made)—not $550,000. The $200,000 in appreciation is not depreciable.
The rule works the other way too. If your home has declined in value—you paid $400,000 and it's worth $340,000 at conversion—your depreciable basis is limited to $340,000 (the FMV). You can't depreciate more than the property is currently worth.
Capital improvements increase your adjusted basis. A kitchen renovation, roof replacement, HVAC upgrade, or addition adds to your original purchase price. If you paid $300,000 and put $80,000 into improvements, your adjusted basis is $380,000. This matters directly for cost segregation—more depreciable basis means more components to reclassify.
How Cost Segregation Applies to Converted Property
Once you've established the correct depreciable basis and subtracted land, cost segregation works the same way it does for any rental property. The study analyzes the building at the component level—flooring, cabinetry, fixtures, appliances, landscaping, driveways, plumbing fixtures, electrical systems—and classifies each component into the appropriate MACRS recovery period.
For a converted single family home, you can typically expect 17–18% of the depreciable basis reclassified into 5-year and 15-year property. If you've furnished the home as a short-term rental, that jumps to 30–34% because furniture, linens, entertainment equipment, and outdoor amenities all qualify as 5-year or 7-year property. (See our full benchmark data by property type.)
The conversion date is your "placed in service" date for depreciation purposes. If you convert the property in March 2026, that's when the depreciation clock starts. With 100% bonus depreciation permanently restored under the One Big Beautiful Bill Act for property placed in service in 2025 and beyond, all reclassified components can be deducted in full in the year you convert.
A Worked Example
Consider a homeowner in Charlotte, NC who bought a 2,400 SF home in 2019 for $375,000 and made $45,000 in capital improvements (new kitchen, deck addition, landscaping). In 2026, the home is worth $520,000. They move out and list it as a long-term rental.
Charlotte, NC — Converted SFR, Unfurnished
The $100,000 in appreciation ($520K FMV minus $420K adjusted basis) is irrelevant to the depreciation calculation. It doesn't help and it doesn't hurt. The cost segregation study works with the $336,000 depreciable basis and reclassifies components from 27.5-year property into shorter recovery periods.
Common Conversion Scenarios
The most common scenario. You buy a new primary residence and rent out the previous one. Your adjusted basis is your original purchase price plus improvements. This is almost always lower than FMV in appreciating markets, so you use the adjusted basis. Cost segregation applies to the full building basis on the conversion date.
Same basis rules, but with a significant cost seg advantage. When you furnish the property for STR use, the furniture and equipment you purchase are separate depreciable assets (5-year or 7-year property) in addition to the building components identified in the study. Between the building-level cost seg and the FF&E, STR conversions often produce 28–34% of the depreciable basis in accelerated categories. If you materially participate in the STR, these deductions may offset W-2 income.
If you rent out your home temporarily while working in another city, the property is still placed in service as a rental during that period. You can depreciate it (and apply cost segregation) for the rental period. If you move back in later, the property converts back to personal use and depreciation stops. The accelerated deductions taken during the rental period remain valid.
In this case, the FMV at conversion is lower than your adjusted basis, so FMV becomes your depreciable basis. This is less common in recent years, but it happens in markets that have corrected. The cost seg study works with the FMV-based basis. The difference between your adjusted basis and FMV cannot be claimed as a loss on conversion—it's only recognized when you eventually sell.
When Does a Cost Seg Study Make Sense on a Converted Residence?
The economics are straightforward. If your building's depreciable basis (after subtracting land) is above roughly $150,000, the Year 1 tax savings from cost segregation will typically exceed the study cost many times over. For a $300,000 depreciable basis at 18% reclassification, you're looking at roughly $54,000 in accelerated deductions—worth $13,000–$20,000 in federal tax savings depending on your bracket.
The study cost for a single family property is $795 (for properties under $1M purchase price). That's a 16:1 to 25:1 return on the study investment for the example above.
A cost seg study is less impactful when the depreciable basis is very low (under $100,000), when the property is a condo with limited depreciable scope, or when the owner plans to sell within 1–2 years and would face depreciation recapture. For a deeper analysis of when cost segregation doesn't make sense, see our detailed guide on that topic.
For inherited property, the rules are different—inherited properties receive a stepped-up basis to FMV at the date of death, which is typically more favorable than the converted-residence basis rules.
Frequently Asked Questions
Yes. Once a primary residence is placed in service as a rental property, it becomes depreciable under MACRS. Cost segregation reclassifies qualifying components—flooring, cabinetry, fixtures, landscaping, driveways—into 5-year, 7-year, and 15-year recovery periods. The only difference from a property purchased as an investment is how you calculate the starting basis: it's the lower of adjusted basis or FMV at conversion.
Under IRS rules, your depreciable basis is the lower of: (1) your adjusted basis (original purchase price plus capital improvements, minus any casualty loss deductions), or (2) the fair market value on the date of conversion. You then subtract the land value to arrive at the building's depreciable basis. In most appreciating markets, the adjusted basis will be lower, which means appreciation does not increase your depreciable amount.
Appreciation doesn't change the analysis much. Your depreciable basis is capped at the adjusted basis regardless of how much the home has appreciated. The question is whether your adjusted basis minus land produces enough depreciable basis to justify the study. For most converted residences with $150,000+ in building depreciable basis, the answer is yes—the Year 1 tax savings from reclassifying 17–18% of the basis into accelerated categories far exceeds the $795 study cost.
Related Articles
Cost Segregation for Inherited Property
How stepped-up basis works and why inherited property is often the best candidate for cost segregation.
When Not to Do Cost Segregation
Cost seg isn't right for every property. Here's how to know if the economics work for yours.
Cost Segregation Benchmarks by Property Type
What percentage to expect from a cost seg study, broken out by residential and commercial property types.