How long do you depreciate a commercial roof for IRS taxes?

Replacing the roof on a business property is expensive, and the way you report it affects your taxes for decades. Instead of deducting the entire cost in the year of installation, the IRS requires you to recover that investment over time. This post clarifies how long you depreciate a commercial roof for IRS purposes, contrasts the treatment with residential rental roofs and summarizes ways to accelerate deductions under recent tax law.

Understanding Commercial Roof Depreciation

Depreciation spreads out the cost of an asset over its useful life. Under the Modified Accelerated Cost Recovery System (MACRS), nonresidential real property—including the roof of a commercial building—must be depreciated over 39 years. You take an equal deduction each year using the straight‑line method, with a partial deduction in the month the roof is placed into service.

Residential rental property follows a 27.5‑year schedule. That means a roof on an apartment building or duplex depreciates faster than a roof on an office or warehouse. The physical lifespan of your roof—whether it lasts 20 years or 40—doesn’t change the tax schedule.

Repairs vs. Improvements

Not every roofing cost is depreciated. Routine maintenance—patching leaks, replacing a few shingles or cleaning gutters—is treated as a repair and can be expensed in the year incurred. Replacing the entire roof or upgrading materials is a capital improvement. Because it restores a major component of the building, it must be capitalized and depreciated. Documenting the scope of work helps if the IRS questions whether a job was a repair or an improvement.

The 39‑Year Rule

For a full roof replacement on a commercial building, the IRS requires depreciation over 39 years. Each new roof starts its own depreciation schedule. Even if your roof wears out sooner, you cannot accelerate the write‑off unless part of the work qualifies for special treatment. Residential rental roofs use the 27.5‑year schedule.

Some owners ask whether a roof can be depreciated over 15 years. Only qualified improvement property (QIP)—improvements to the interior of a nonresidential building—uses a 15‑year schedule. Roofs typically don’t qualify because they’re part of the building envelope, though installing skylights or insulation that affects the interior may allow a portion of the cost to be depreciated faster. Certain tax‑exempt entities must use the Alternative Depreciation System (ADS), which assigns a 40‑year recovery period.

Accelerating Deductions: Section 179 and Bonus Depreciation

Waiting nearly four decades to recover a roof’s cost can strain cash flow. Two tax provisions—Section 179 and bonus depreciation—allow you to write off costs sooner.

Section 179 lets businesses deduct the cost of qualifying property in the year it’s placed into service. The Tax Cuts and Jobs Act expanded Section 179 to include improvements to nonresidential real property such as roofs, HVAC systems and fire protection. The One Big Beautiful Bill Act (OBBBA) enacted in 2025 raised the Section 179 limit to $2.5 million and set a phase‑out threshold at $4 million. This means many businesses can expense their roof project rather than depreciate it. The deduction cannot create or increase a net operating loss, and it generally applies only to businesses actively using the property.

Bonus depreciation allows you to deduct a percentage of an asset’s cost in the year it’s placed into service. The OBBBA restored 100% bonus depreciation for property acquired after January 19, 2025. Bonus depreciation generally applies only to assets with a recovery period of 20 years or less, so commercial roofs don’t qualify directly. However, a cost segregation study may identify interior components of a roof project—such as skylights—that meet the definition of qualified improvement property and therefore qualify for bonus depreciation. Businesses may elect a 40% bonus rate instead of 100% to align deductions with income.

Planning and Practical Tips

Understanding how long to depreciate a commercial roof for IRS taxes is only part of the equation. Consider these steps when planning a Roof Installation or Roof Replacement:

1. Classify costs correctly. Repairs are deducted immediately; improvements are capitalized. Keep detailed records to support your classification.
2. Use Section 179 when available. If your roof project cost falls below the Section 179 limit and you actively use the property, expensing it can free up cash.
3. Explore bonus depreciation. Identify portions of your project that qualify as interior improvements; those costs may be eligible for bonus depreciation. A cost segregation study can help.
4. Maintain the roof. Routine maintenance extends the roof’s physical life and is deductible immediately. Regular inspections and repairs also reduce the likelihood of premature replacement.
5. Plan for insurance and resale. Depreciation affects insurance payouts and capital gains. For guidance on how roof age factors into insurance, see How old may a roof be before insurance claims it’s too old?.
6. Work with professionals. Tax rules evolve. Recent changes—the expansion of Section 179 and the reinstatement of 100% bonus depreciation—illustrate how quickly the landscape can shift. Consult a tax advisor and partner with a reputable Worthington Roof Company to maximize your benefits.

Table: Tax Treatment of Roof Costs

Conclusion

So, how long do you depreciate a commercial roof for IRS taxes? In most cases the answer is 39 years for commercial property and 27.5 years for residential rental property. Only interior improvements that meet the definition of qualified improvement property may use a 15‑year schedule, and they’re the exception rather than the rule. Waiting decades to recover costs isn’t the only option: Section 179 now allows many businesses to expense roof projects up to $2.5 million, and bonus depreciation has been restored to 100% for qualifying components. By classifying your roof work correctly, leveraging available tax incentives and working with experts, you can protect your investment and manage cash flow more effectively. Whether you're budgeting for a new Roof Installation or planning a Roof Replacement with a Worthington Roof Company, understanding depreciation helps you make better decisions.

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