Most of what gets written about cost segregation assumes you bought the property, an existing house or a finished cabin that changed hands, and the study reverse-engineers what the components were worth out of the purchase price. But a lot of residential investors aren't buying. They're building: a build-to-rent single-family, a new short-term rental cabin, an accessory dwelling unit in the backyard. The question we hear is whether cost segregation even applies to something you put up yourself, and if so, whether it's worth the trouble on a brand-new building.
The short answer is yes on both counts. New construction is often the cleanest, best-supported study we do.
Can you even do a cost segregation study on a property you built yourself?
Yes. A study doesn't care whether the building was bought or built. Its job is the same either way: identify the components of the property that qualify for shorter IRS recovery periods than the 27.5 years residential real estate is normally depreciated over, and move them out of that long bucket into 5-, 7-, and 15-year buckets. Cabinetry, flooring, specialty electrical and plumbing tied to appliances, decorative finishes, driveways, landscaping, fencing, exterior lighting, these wear out faster than the structure, and they qualify whether a contractor installed them last month or a prior owner installed them a decade ago.
What changes with new construction isn't whether you can do it. It's the quality of what you're working from.
Why new construction is the cleanest study you'll ever get.
On a purchase, the engineer starts with one number, the price you paid, and allocates it across components using measurements, takeoffs, and cost data. It's a defensible process, but it is fundamentally an estimate.
On a build, you don't estimate. You have the actual costs: the contractor's schedule of values, pay applications, subcontractor invoices, change orders, and the final construction ledger. Every dollar that went into the property is documented and already broken out by trade. That means the reclassification is built on real, itemized numbers instead of a modeled split, which makes it both more accurate and easier to stand behind if the return is ever examined. It also tends to reclassify a higher share of basis, because line-item detail catches short-life property that a top-down allocation can miss.
Does 100% bonus depreciation apply to a new build?
This is where the timing matters. The One Big Beautiful Bill restored 100% bonus depreciation for property acquired after January 19, 2025, which is what makes the reclassified portion fully deductible in year one instead of spread over the shorter schedules. For a property you build rather than buy, the "acquired" test for self-constructed property generally looks to when physical construction of the property began, so a build that broke ground after January 19, 2025 lands in the 100% window. If you started construction before that date, the older phase-down rates may apply instead, so confirm your specific timeline with your CPA before counting on the full write-off. We cover the restored 100% rule in more detail in our note on why bonus depreciation is back.
The other date that matters is when the property is placed in service, which for a rental means it's ready and available to rent, typically once you have a certificate of occupancy and the unit is listed or otherwise available. That's the year the deduction lands. You don't depreciate anything while the building is still going up; the costs sit capitalized until the property is in service.
The math, for a $480K new build.
Take a build-to-rent single-family that costs $480K all-in, placed in service in 2026. Land is carved out first, since land is never depreciable, say $80K, leaving $400K of building basis on the 27.5-year schedule.
Because you have the full construction ledger, a residential study on a new build can reasonably reclassify around 25% of that basis into shorter-life property, sometimes more when the finishes and site work are extensive. Call it $100K moving out of 27.5-year and into the 5-, 7-, and 15-year buckets.
Without bonus depreciation, you'd still deduct that $100K faster than 27.5 years, but spread across those shorter periods. With 100% bonus depreciation in effect, the entire $100K is deductible the year the property is placed in service. At a 32% marginal federal rate, that's roughly $32,000 in year-one tax savings, before any state benefit. The land split and the reclassification percentage drive that number, which is exactly why having the real build records helps, and it's why the land value allocation is worth getting right from the start.
What trips people up on a new build.
Three things. First, timing: no depreciation runs until the property is placed in service, so a home that's still framed at year-end doesn't produce a deduction yet, no matter how much you've spent. Second, the land: on a build, land is often a clean separate number from your closing, so use it, don't let the whole project cost get depreciated. Third, the records: the single biggest advantage of a new build is the construction detail, and the single biggest way to waste it is to not keep the pay applications, invoices, and final cost breakdown. Hold onto them. They're what makes the study audit-ready.
What to do if you're building now.
If you have a residential rental under construction, the move is to get the cost records organized as you go rather than reconstructing them later, and to note your construction start date and expected placed-in-service date. From there, a short feasibility call will tell you candidly whether a study pencils for your project and your tax situation, or whether it doesn't. There are builds where it isn't worth it, and we'll say so. If you've got a CPA, we work alongside them and hand over a deliverable they can implement without translating anything. Start with a feasibility review or run the rough numbers on the savings estimate first.