How Long to Depreciate Building Improvements Under Current IRS Rules

The depreciation period for building improvements is determined by the classification of the underlying real estate and the specific nature of the work performed. Under the Modified Accelerated Cost Recovery System (MACRS) used in the United States, building improvements generally fall into recovery periods of 15, 27.5, or 39 years. Improvements to residential rental properties are depreciated over 27.5 years, while structural improvements to commercial buildings typically require 39 years. However, specific internal enhancements known as Qualified Improvement Property (QIP) may qualify for a shorter 15-year recovery period.

Understanding these timelines is essential for tax planning and cash flow management. Failing to correctly categorize an improvement can lead to missed deductions or potential penalties during an Internal Revenue Service (IRS) audit.

Distinguishing Between Repairs and Capital Improvements

Before determining a depreciation schedule, it is necessary to establish whether an expenditure is a deductible repair or a capital improvement. The IRS applies the "BAR" test to make this distinction, which stands for Betterment, Adaptation, and Restoration.

The Betterment Standard

An expenditure qualifies as a betterment if it corrects a defect that existed before the property was acquired, or if it results in a material addition to the property. For example, expanding the square footage of a building is a betterment. Similarly, if an improvement increases the productivity, efficiency, or quality of a building system, it must be capitalized and depreciated.

The Adaptation Standard

Adaptation involves modifying a property for a use that is different from its original intended purpose. If a building owner converts a residential garage into a commercial retail space, the costs associated with that conversion are considered capital improvements. Because the asset is being adapted to a new use, these costs cannot be deducted as current expenses.

The Restoration Standard

Restoration occurs when a building or a building system is returned to its ordinary operating condition after it has fallen into a state of disrepair. Replacing a major component of a building, such as the entire roof or the HVAC system, is considered a restoration. These projects are capital improvements because they extend the useful life of the asset.

In contrast, routine maintenance—such as fixing a leaky faucet, replacing a few broken shingles, or repainting a room—is generally considered a repair. Repairs are fully deductible in the year the expense is incurred, providing an immediate tax benefit compared to the multi-year timeline of depreciation.

Residential Rental Property: The 27.5-Year Recovery Period

For buildings classified as residential rental property, the standard depreciation period for structural improvements is 27.5 years. This timeline applies to apartment buildings, duplexes, and single-family homes used as rentals.

The 80 Percent Income Test

A building is only classified as residential rental property if 80 percent or more of its gross rental income is derived from dwelling units. This is a critical distinction for mixed-use buildings. For instance, a property with a retail store on the ground floor and apartments on the upper floors must meet this income threshold to qualify for the 27.5-year schedule. If the retail space generates 25 percent of the total income, the entire building and any structural improvements made to it must be depreciated over 39 years as nonresidential property.

Common Residential Improvements

Improvements that typically fall under the 27.5-year schedule include:

• Complete roof replacements.
• Installation of new plumbing or electrical wiring throughout the building.
• Replacement of all windows and doors.
• Substantial flooring upgrades that are considered permanent.

These assets must use the straight-line depreciation method, meaning the deduction is spread evenly over the 27.5-year lifespan.

Nonresidential Commercial Property: The 39-Year Recovery Period

Nonresidential real property includes office buildings, warehouses, retail stores, and industrial facilities. Structural improvements to these buildings are depreciated over 39 years using the straight-line method.

The longer recovery period for commercial assets reflects the IRS's view on the durable nature of commercial structures. Because structural changes—such as adding a new floor, reinforcing the foundation, or expanding the building's footprint—impact the core integrity of the property, they are tied to the primary building's depreciation life.

Examples of 39-Year Assets

Work that generally requires a 39-year depreciation schedule includes:

• Building additions and expansions.
• Structural framing modifications.
• Installation or replacement of elevators and escalators.
• Fire suppression systems that are integrated into the building's structure.

The 15-Year Exception: Qualified Improvement Property (QIP)

The most significant opportunity for accelerated depreciation in commercial real estate is Qualified Improvement Property (QIP). Introduced as part of recent tax reforms, QIP allows certain interior improvements to nonresidential buildings to be depreciated over just 15 years instead of 39.

Requirements for QIP

To qualify as QIP, the improvement must meet three specific criteria:

1. Interior Only: The work must be performed on the interior portion of the building.
2. Placed in Service After the Building: The improvement must be made after the building was originally placed in service.
3. Non-Structural: The improvement cannot involve the internal structural framework of the building.

Exclusions from QIP

Even if the work is performed on the interior, the IRS explicitly excludes certain projects from the 15-year QIP classification. These include:

• The enlargement of the building.
• Any elevator or escalator.
• Modifications to the building’s structural frame, such as load-bearing walls.

For example, if a tenant in an office building installs new interior partitions, lighting fixtures, and flooring, these costs likely qualify as QIP and can be depreciated over 15 years. However, if that same tenant moves a load-bearing wall to create a larger conference room, that specific cost must be depreciated over 39 years.

Strategic Value of QIP

The 15-year recovery period is advantageous because it allows for faster capital recovery. Furthermore, 15-year property is often eligible for bonus depreciation, which can allow for a 100 percent deduction in the first year the improvement is placed in service.

Land Improvements and the 15-Year Schedule

Not all improvements are part of the building itself. Enhancements to the land surrounding the building have their own depreciation rules. Most land improvements use a 15-year recovery period.

Defining Land Improvements

Land improvements are depreciable assets that are not part of the building structure but are attached to the land and have a limited useful life. Common examples include:

• Paving: Asphalt or concrete parking lots, sidewalks, and driveways.
• Fencing: Perimeter fences, gates, and decorative walls.
• Landscaping: Permanent shrubs, trees, and irrigation systems.
• Lighting: Outdoor parking lot lights and security lighting.

While land itself is never depreciable (as it does not wear out), these improvements deteriorate over time and thus qualify for a 15-year write-off. In our analysis of commercial property portfolios, maximizing the allocation to land improvements is a standard method for increasing early-stage tax deductions.

Personal Property Classified within Building Projects

During a renovation or construction project, building owners often purchase items that are not legally "real property." These are classified as personal property and typically have much shorter recovery periods—often 5 or 7 years.

The 5-Year and 7-Year Categories

• 5-Year Property: Includes items like computers, office machinery, and appliances (refrigerators, stoves) in residential rental units. It also covers decorative items like carpeting (if not permanently glued down) and specialty lighting.
• 7-Year Property: Includes office furniture, fixtures, and specialized equipment used in business operations.

By identifying these assets separately from the general building improvement project, owners can significantly accelerate their depreciation deductions. This process is often facilitated by a professional cost segregation study.

Accelerated Depreciation: Section 179 and Bonus Depreciation

While the 15, 27.5, and 39-year schedules provide the baseline for depreciation, tax laws often allow for immediate expensing of certain improvements.

Section 179 Expensing

Section 179 of the Internal Revenue Code allows taxpayers to deduct the full cost of certain building improvements in the year they are placed in service, rather than depreciating them over several years. For 2026 and beyond, this deduction is subject to specific dollar limits and phase-out thresholds.

Qualifying improvements for Section 179 in nonresidential buildings include:

• Roofs.
• HVAC systems.
• Fire protection and alarm systems.
• Security systems.

It is important to note that Section 179 deductions cannot exceed the taxable income of the business. If the business is operating at a loss, the deduction must be carried forward to future years.

Bonus Depreciation

Bonus depreciation allows a business to immediately deduct a large percentage of the cost of eligible property. Historically, this rate was 100 percent, but it began a phase-down schedule in recent years. However, under the latest legislative updates, 100 percent bonus depreciation has been restored for qualified property acquired after early 2025.

QIP and land improvements are generally eligible for bonus depreciation because they have a recovery period of 20 years or less. Standard residential (27.5 years) and commercial (39 years) structural improvements do not qualify for bonus depreciation because their recovery periods are too long.

Convention Rules: The Mid-Month and Mid-Quarter Conventions

The IRS does not allow a full year of depreciation in the year an improvement is placed in service unless it was placed in service on the first day of the year. Instead, specific "conventions" are used to determine how much depreciation is allowed in the first and last years.

Mid-Month Convention

Real property (27.5-year and 39-year assets) follows the mid-month convention. Under this rule, the property is treated as being placed in service in the middle of the month, regardless of whether the work was finished on the 1st or the 30th. For example, an improvement placed in service in August would receive 4.5 months of depreciation for that first year.

Mid-Quarter and Half-Year Conventions

Personal property (5-year and 7-year assets) and some land improvements use either the half-year or mid-quarter convention. The half-year convention treats all property placed in service during the year as being placed in service at the midpoint of the year. However, if more than 40 percent of the total value of all personal property is placed in service during the fourth quarter, the mid-quarter convention must be used, which can reduce the first-year deduction.

The Role of Cost Segregation Studies in Optimizing Depreciation

A cost segregation study is a professional analysis used to identify and reclassify building components to accelerate depreciation. By breaking down a lump-sum building improvement project into its constituent parts, engineers and accountants can move costs from the 39-year category into the 15, 7, or 5-year categories.

Practical Impact of Cost Segregation

Consider a $1 million renovation of a commercial office space. Without a cost segregation study, the entire $1 million might be depreciated over 39 years, resulting in a modest annual deduction.

Through cost segregation, an analyst might find:

• $400,000 in Qualified Improvement Property (15 years).
• $100,000 in decorative lighting and specialty electrical for equipment (5 years).
• $50,000 in dedicated cooling systems for a server room (5 years).
• $450,000 in structural changes (39 years).

By reclassifying over half of the project into shorter-lived categories—many of which may also be eligible for 100 percent bonus depreciation—the building owner can significantly increase their tax savings in the first year.

Special Considerations for Mixed-Use and Multi-Family Buildings

In multi-family and mixed-use environments, the depreciation rules can become complex. The classification of an improvement often depends on its location within the building.

Common Areas

Improvements to common areas in a residential building, such as lobbies or hallways, are depreciated over 27.5 years. In a commercial building, these same areas would be 39-year assets or potentially 15-year QIP if they meet the interior requirements.

Tenant Improvements

In commercial leases, "tenant improvements" (TI) are often funded by the landlord. If the landlord owns these improvements, they depreciate them over 39 years (or 15 years if they qualify as QIP). If the tenant moves out and the improvements are abandoned or destroyed, the remaining undepreciated basis can often be written off in the year of disposal.

Summary of Building Improvement Depreciation Periods

Navigating the various recovery periods requires a clear understanding of the IRS asset classes. The following table summarizes the standard durations for various types of improvements:

Choosing the correct period is not just a matter of compliance; it is a critical component of real estate investment strategy. By leveraging QIP, Section 179, and cost segregation, property owners can maximize their after-tax returns.

Conclusion

The time required to depreciate building improvements ranges from as little as 5 years for personal property to as long as 39 years for commercial structural components. The 27.5-year period remains the standard for residential rentals, while the 15-year QIP classification offers a powerful incentive for commercial interior renovations. Because tax laws regarding bonus depreciation and expensing limits are subject to change, building owners should regularly review their capitalization policies and consult with tax professionals to ensure they are utilizing the most beneficial depreciation strategies available.

Frequently Asked Questions

Can I depreciate the cost of a new roof over 15 years?

Generally, no. A new roof is a structural component. For a residential rental, it is depreciated over 27.5 years. For a commercial building, it is depreciated over 39 years. However, under Section 179, some commercial building owners may be able to expense the full cost of a roof replacement in a single year, provided they meet the income and investment limits.

What is the difference between QIP and standard commercial improvements?

Qualified Improvement Property (QIP) refers specifically to interior, non-structural improvements made to an existing commercial building. Because QIP has a 15-year recovery period, it is eligible for bonus depreciation. Standard commercial improvements, such as building additions or external structural work, are depreciated over 39 years and are not eligible for bonus depreciation.

Does painting count as an improvement?

By itself, painting is usually considered a repair and is fully deductible in the year the cost is incurred. However, if the painting is part of a larger capital improvement project—such as a complete building renovation—it must be capitalized and depreciated over the same period as the rest of the project.

How does the 80% rule affect my mixed-use building?

If 80% or more of your gross rental income comes from dwelling units, your building is "residential rental property," and improvements are depreciated over 27.5 years. If your commercial tenants contribute more than 20% of the total income, the building is "nonresidential," and improvements must be depreciated over 39 years.

Is landscaping always depreciated over 15 years?

Most permanent landscaping, such as trees, shrubs, and irrigation systems, falls into the 15-year land improvement category. However, if the landscaping is part of the initial construction and is so closely tied to the building that it would be destroyed if the building were replaced, it might be required to follow the building's 27.5 or 39-year schedule.