House hacking, buying a property, living in part of it, and renting out the rest, has moved from a niche idea to a mainstream wealth-building strategy. The share of homebuyers who say the ability to rent out part of their home matters rose from 27% in 2018 to 39% in 2023, according to Zillow survey research.
Many house hackers assume they cannot depreciate a home they live in. That assumption is wrong, and it can leave real money on the table.
The IRS allows depreciation on the portion of a mixed-use property used for rental (IRS Publication 527). A basement apartment, a duplex unit, or an accessory dwelling unit (ADU), if a tenant pays rent for a defined space, that space is generally depreciable. Cost segregation can then accelerate those deductions.
This article explains how partial-property depreciation works, how to calculate your rental-use percentage, how a cost segregation study applies to the rental portion, and the IRS rules that keep you compliant.
Can You Depreciate a Property You Live In?
Yes, but only the portion used for rental purposes.
The IRS requires owners of mixed-use property to allocate expenses between personal and rental use. The rental portion qualifies for depreciation and deductible expenses. The personal portion does not.
Common scenarios:
- Basement apartment: you live upstairs, and a tenant rents the finished basement.
- Duplex or triplex: you occupy one unit and rent the others.
- ADU: a separate structure on your property rented to a tenant.
- Spare rooms: rented short-term through platforms like Airbnb or VRBO. Note: shared-space rentals in a home you also occupy often trigger the Section 280A deduction cap, see the compliance section below.
The allocation is usually based on square footage. If a 2,500-square-foot home includes a 750-square-foot rental unit, the rental-use percentage is 30% (750 ÷ 2,500). Only that 30% of the depreciable basis qualifies for rental depreciation.
How to Calculate Your Rental-Use Percentage
The IRS lets you divide expenses by any reasonable method, and specifically mentions square footage or number of rooms.
Square Footage Method (Recommended)
Divide the rental square footage by the total livable square footage. It is the most common and most defensible approach.
Formula: Rental Square Footage ÷ Total Square Footage = Rental-Use Percentage.
A 3,000-square-foot property with a 1,000-square-foot rental unit is 33% rental use.
Number of Rooms Method
Divide the rental rooms by the total rooms. This method is acceptable but less precise when rooms vary in size.
Handling Shared Spaces
Shared areas such hallways, a common laundry room, or a shared kitchen call for judgment. Exclude them from the rental allocation unless the tenant has exclusive or primary use. A tenant with a private entrance, bathroom, and kitchen makes the allocation cleaner. Where spaces are shared, document a reasonable, consistent method.
Documentation tips:
- Keep a floor plan with the rental and personal areas clearly marked.
- Maintain a signed lease for the rental space.
- Photograph the rental unit, inside and at its access points.
- Use the same allocation method every year.
Cost Segregation on the Rental Portion
Once you set the rental-use percentage, that share of the depreciable basis is eligible for a cost segregation study.
A study puts engineers to work reclassifying building components into shorter asset recovery periods, 5, 7, and 15 years, instead of leaving everything on the 27.5-year residential schedule (IRS Publication 946). With bonus depreciation, the reclassified components can be deducted immediately.
A quick note on timing. Under the One Big Beautiful Bill Act, 100% bonus depreciation is now permanent. It applies to qualified property acquired after January 19, 2025 and placed in service after that date (IRS guidance). Binding contracts entered into on or before January 19, 2025 generally stay on the old phase-down schedule, even if the property is placed in service later. For look-back studies, use the property's original placed-in-service year, not the study year.
Confirm both the acquisition date and placed-in-service date before modeling deductions.
Here is the math. The figures are illustrative, land ratios and reclassification percentages vary by property.
Take a $500,000 home with 30% rental use. Assume land is 15% of value, since land is never depreciable. That leaves a $425,000 depreciable basis. The rental portion is $425,000 × 30% = $127,500.
Suppose a study reclassifies 28% of that rental basis, $35,700, into shorter-life categories.
First-year deductions on the rental portion:
- Bonus depreciation on reclassified components: $35,700
- Standard depreciation on the remaining $91,800 ($91,800 ÷ 27.5): about $3,300
- Total first-year rental deduction: about $39,000
At a 37% marginal rate, that is roughly $14,400 in first-year tax savings, if you can use the deduction this year (see "Can You Actually Use the Deduction?" below). Without cost segregation, annual depreciation would be about $4,600 ($127,500 ÷ 27.5). The first-year difference is more than $34,000 in additional deductions.
Is a partial-property study worth it?
There is no strict property-value threshold. The real question is whether projected tax savings outweigh the study fee. A larger rental basis, say, a 50% allocation on a higher-value property, makes the case easily. A small rental basis may not justify a full study, though smaller properties can still pencil out with a lower-cost report. Decide with your CPA based on your tax situation.
IRS Rules You Must Follow
Partial-property depreciation is a legitimate strategy with clear requirements.
Define the rental space. A vague claim that "part of the house is rented" will not hold up. The unit should have physical boundaries, a defined floor plan, and ideally a separate entrance.
Keep a legitimate rental arrangement. Maintain a signed lease and documented rent, and report the income on Schedule E. Renting to a family member below fair market rent can convert those days to personal use and disqualify the deductions (IRS Topic No. 415).
Watch Section 280A. Section 280A can limit deductions when you rent part of a dwelling unit you also live in (Internal Revenue Code Section 280A). In that case, rental deductions may be capped at rental income, enough to wipe out the first-year loss you expected. A self-contained unit with a separate entrance, kitchen, and bath is generally treated as its own dwelling unit and avoids this cap. A shared basement that is part of your own living space is more likely to trigger the limit.
Apply the allocation consistently. Claiming 30% rental use means 70% of expenses, including depreciation, are nondeductible personal costs.
Converting personal space to rental? Your depreciable basis is the lesser of your adjusted basis or the property's fair market value at conversion (Publication 527). Depreciation starts on the conversion date. If the rental portion was already being depreciated on the 27.5-year schedule and you later do a cost segregation study, the catch-up is claimed on Form 3115.
Plan for recapture. Accelerated deductions are recaptured when you sell. The tax treatment follows three buckets: (1) 5- and 7-year personal property reclassified under §1245: depreciation taken is recaptured at ordinary income rates; (2) 15-year land improvements treated as §1250 real property: any depreciation in excess of straight-line is recaptured at ordinary rates, and the remainder is unrecaptured §1250 gain taxed at a maximum 25%; (3) 27.5-year residential real property: unrecaptured §1250 gain taxed at a maximum 25%. Factor recapture across all three categories into your hold-and-sell plan.
Red flags that draw IRS scrutiny:
- Claiming rental use with no lease or reported income
- A rental-use percentage that does not match the layout
- Shared-space allocations that look inflated
- Claiming full-property depreciation on a mixed-use home
Can You Actually Use the Deduction?
A large first-year deduction only helps if the tax rules let you apply it this year.
Rental losses are generally passive. For most passive investors, the deduction offsets rental (passive) income and carries forward until you have passive income or sell the property (IRS Publication 925). There are two common ways to use losses against other income:
- Real Estate Professional status plus material participation, which makes the rental nonpassive and can offset W-2 income.
- The short-term rental approach, where material participation in a low-average-stay STR can produce nonpassive treatment.
There is also a limited $25,000 special allowance for active participants. It phases out between $100,000 and $150,000 of modified adjusted gross income. Ask your CPA which rule applies to you.
House Hacking and Cost Segregation
House hacking is a common partial-property scenario, and higher rental percentages produce larger benefits.
A duplex owner who occupies one of two similarly sized units has roughly a 50% rental allocation. A triplex owner occupying one of three similar units has about 67%. Allocate by actual square footage, unequal units change the percentage. The higher the rental share, the larger the depreciable basis.
A duplex example: take a $600,000 property with 50% rental use. After a 15% land allocation, the depreciable basis is $510,000, and the rental portion is $255,000. Say a study reclassifies 30%, $76,500, into 5- and 15-year property. At a 37% rate, 100% bonus depreciation yields about $28,300 in first-year savings on that portion, again only if the deduction is usable.
House hacking already lowers your housing costs through rental income. Cost segregation can add accelerated deductions on top, when your facts and tax profile support it.
Key Takeaways
- You can depreciate the rental portion of an owner-occupied property; you just need a clear allocation (Publication 527).
- Square footage is the most defensible method. Document your floor plan and use it consistently.
- Cost segregation accelerates deductions on the rental portion. A 30% allocation on a $500,000 home can produce roughly $14,400 in first-year savings if the deduction is usable this year.
- 100% bonus depreciation is permanent for property acquired and placed in service after January 19, 2025; earlier acquisitions are generally capped at 40%.
- Compliance requires a defined rental space, a real lease, Schedule E reporting, and attention to Section 280A and recapture.
Living in your property does not disqualify you from powerful depreciation strategies. It just means getting the allocation, and the timing, right.
Want to see how much of your mixed-use property qualifies? Get a free proposal from R.E. Cost Seg and run the numbers for your situation.
