A roof replacement does not qualify for bonus depreciation. Bonus depreciation under IRC Section 168(k) is limited to property with a MACRS recovery period of 20 years or less, and a roof on a commercial building is treated as part of the 39-year structure. The consolation is that Section 179 fills the gap: roofs on nonresidential buildings are specifically listed as eligible for full first-year expensing, so the practical result can be nearly identical to bonus depreciation.
Why a Roof Is Excluded
A commercial building is nonresidential real property with a 39-year recovery period, and the roof is treated as part of that structure.1Internal Revenue Service. Publication 946, How To Depreciate Property That puts it well past the 20-year ceiling for bonus depreciation eligibility.
The one classification that would shorten the life is Qualified Improvement Property, which carries a 15-year recovery period and qualifies for 100 percent bonus depreciation. But QIP applies only to improvements made to the interior portion of a nonresidential building. A roof is an exterior component, so it doesn’t fit the definition.1Internal Revenue Service. Publication 946, How To Depreciate Property
Publication 946 makes the split visible: it defines QIP as interior improvements only, and then separately lists roofs as a category of qualified Section 179 real property. If roofs were QIP, the separate Section 179 listing would be unnecessary.
Section 179 Is the Working Alternative
Under IRC Section 179(e), a roof replacement on a nonresidential building qualifies as “qualified real property” eligible for full first-year expensing, provided the improvement is made after the building was originally placed in service.1Internal Revenue Service. Publication 946, How To Depreciate Property The tax code names four nonresidential improvements that are Section 179-eligible even though they don’t qualify as QIP:
- Roofs
- Heating, ventilation, and air-conditioning property
- Fire protection and alarm systems
- Security systems
For tax year 2026, the maximum Section 179 deduction is approximately $2,560,000, with the phase-out beginning when total qualifying property placed in service exceeds approximately $4,090,000. These figures adjust for inflation. Most roof replacements sit well below the cap, so the entire cost can typically be written off in year one.
There is one meaningful catch. Section 179 cannot exceed the taxpayer’s net taxable business income for the year. If a business shows $200,000 of taxable income and spends $350,000 on a new roof, Section 179 covers $200,000 in year one and the remaining $150,000 carries forward. Bonus depreciation has no such limit and can create or deepen a net operating loss. For a large roof outlay in a lean year, this income cap is the main disadvantage of going the Section 179 route.
Residential Rental Property Doesn’t Get Either Benefit
The Section 179 categories above apply only to nonresidential real property. A roof on a residential rental building is depreciated over 27.5 years as part of the structure, which is both too long for bonus depreciation and outside the Section 179 categories.1Internal Revenue Service. Publication 946, How To Depreciate Property A landlord replacing the roof on an apartment building capitalizes the cost and depreciates it straight-line over 27.5 years. A cost segregation study is the only real avenue for accelerating any portion of the expense.
Is the Work Actually a Capital Improvement?
None of this matters if the roof work is a deductible repair, because a repair is written off immediately without invoking Section 179 or bonus depreciation at all.
Under the tangible property regulations, a capital improvement is an expenditure that results in a betterment, adaptation, or restoration of the property.2Internal Revenue Service. Tangible Property Final Regulations A full roof replacement almost always meets the restoration test because the roof is a major building component. If the work replaces load-bearing structural elements supporting more than 40 percent of the roof, or replaces more than 40 percent of the insulation layer, the IRS treats the entire cost as capital. Patching a leak or swapping out a section of flashing is generally a repair.
Cost Segregation Can Rescue Some Components
Even though the roof itself is either 39-year property or Section 179 qualified real property, a roofing project often includes pieces that legitimately belong in shorter asset classes. Electrical conduit, drainage systems, specialized ventilation equipment, and certain mechanical components installed as part of the job may qualify as 5-year, 7-year, or 15-year property depending on function. Those reclassified components are eligible for 100 percent bonus depreciation.
A cost segregation study performed by a qualified engineer or specialist firm identifies and documents these reclassifications. On a large commercial replacement, the reclassified amounts can be significant. The IRS has issued audit technique guides for cost segregation, and reclassifications that lack engineering support tend to draw questions on exam.
The 163(j) Election Wrinkle
A real estate business that has elected to be an “electing real property trade or business” under IRC Section 163(j)(7)(B) to avoid the business interest expense limitation must depreciate nonresidential real property, residential rental property, and QIP using the Alternative Depreciation System.3Internal Revenue Service. Questions and Answers About the Limitation on the Deduction for Business Interest Expense ADS property is not eligible for bonus depreciation, which affects any interior QIP work you might have done alongside the roof. Section 179, however, is not tied to MACRS versus ADS, so the roof itself can still be expensed under Section 179 after the election.
How to Claim the Deduction on Form 4562
Both Section 179 and bonus depreciation deductions are reported on Form 4562 for the year the roof is placed in service.4Internal Revenue Service. About Form 4562, Depreciation and Amortization
The Section 179 election for the roof goes in Part I. The elected amount reduces the depreciable basis of the asset. Any components reclassified as bonus-eligible through a cost segregation study go in Part II as the special depreciation allowance. Whatever basis remains after those two steps drops into Part III for regular MACRS depreciation over 39 years.5Internal Revenue Service. Instructions for Form 4562
The total flows to the appropriate line of the business return: Schedule C for a sole proprietor, Form 1065 for a partnership, Form 1120-S for an S corporation, or Form 1120 for a C corporation. Keep contractor invoices that separate labor, materials, and component costs; that documentation is what supports the Section 179 election and any cost segregation reclassifications if the return is examined.
Check Your State’s Rules
Federal and state depreciation treatment often diverge. Most states have historically decoupled from federal bonus depreciation to protect their revenue bases, and the permanent restoration of 100 percent bonus depreciation under the One Big Beautiful Bill Act may push more states to decouple.6Internal Revenue Service. Treasury, IRS Issue Guidance on the Additional First Year Depreciation Deduction Amended as Part of the One Big Beautiful Bill A business that fully expenses a roof at the federal level may have to add back part of the deduction on the state return and depreciate the roof over the standard recovery period for state purposes. Confirm your state’s conformity rules before assuming the federal treatment carries through.