Real Estate Tax Calc
The QIP definition and the "interior" requirement
Qualified improvement property is defined in IRC §168(e)(6) as any improvement to an interior portion of a building that is nonresidential real property, placed in service after the building was first placed in service, and not attributable to an enlargement, elevator, escalator, or the building's internal structural framework. The word "interior" is the linchpin. Congress specifically designed QIP to cover the kind of build-out work tenants and owner-occupants do inside commercial spaces — not the exterior shell of the building.
The IRS has consistently maintained this distinction. The preamble to Treasury regulations under §168 confirms that the exterior envelope of the building — roof, walls, windows, facade — is part of the structural shell and is not an "interior portion." A taxpayer cannot reclassify a roof as QIP simply because the work is substantial or because it benefits the interior of the building. The test is where the improvement is physically located, not what it does for the occupants.
Why a roof does not qualify as QIP
A roof is a structural component of the building. Under Treas. Reg. §1.48-1(e)(2), structural components include walls, ceilings, permanent floors, windows, doors, wiring, plumbing, central heating and air conditioning systems, and other components that are "structural parts of, or otherwise permanently attached to, the building." A roof is explicitly an exterior structural component.
The QIP category is also specifically restricted by three additional exclusions. Even if the "interior" requirement were somehow met, a roof improvement that is part of the building's load-bearing structure or that affects the building's structural framework would still fail the "internal structural framework" exclusion. The statutory language in §168(e)(6)(B) excludes any improvement "attributable to (i) the enlargement of the building, (ii) any elevator or escalator, or (iii) the internal structural framework of the building." A roof ties directly to the structural framework.
The result is clear: a roof replacement, roof repair that rises to the level of an improvement, or a new green roof system cannot be classified as QIP. You cannot claim the 15-year MACRS life, you cannot claim bonus depreciation, and you cannot use the §168(k) first-year write-off for this cost.
How a commercial roof is classified and depreciated
A roof on a nonresidential commercial building is a structural component depreciable as 39-year MACRS property under the General Depreciation System. The method is straight-line, and the applicable convention is the mid-month convention (the same as the building itself). The roof improvement is added to the building's depreciable basis and recovered evenly over 39 years.
Under the Alternative Depreciation System (ADS), the ADS life for nonresidential real property is 40 years. Taxpayers required to use ADS (e.g., those making the §163(j)(7) election) would depreciate the roof over 40 years.
For a residential rental building, the roof is part of the 27.5-year structural asset. A new roof on a residential rental is added to the building's depreciable basis and recovered over the remaining 27.5-year life of the building (or a new 27.5-year period if segregated). Section 179 does not apply to residential rentals, and bonus depreciation does not apply to 27.5-year property.
The Section 179 roofing election for nonresidential property
The TCJA added §179(f)(1), which expanded the definition of §179 qualifying property to include certain improvements to nonresidential real property. The statute specifically lists four categories of nonresidential real property improvements eligible for §179:
- Qualified improvement property (interior improvements)
- Any roof
- Any heating, ventilation, and air-conditioning property
- Any fire protection and alarm system
- Any security system
A roof on a nonresidential building can therefore be elected as §179 property and immediately expensed in the year it is placed in service — but only up to the annual §179 dollar limit (indexed for inflation each year) and subject to the §179 taxable income limitation. Unlike bonus depreciation, §179 cannot create or increase a net operating loss. The deduction is capped at the taxpayer's taxable income from active trades or businesses, and any amount that exceeds the limit is carried forward.
Bonus depreciation — does it apply to roofs?
Bonus depreciation under §168(k) applies only to property with a MACRS recovery period of 20 years or fewer (or property in certain other categories not relevant here). A commercial roof is 39-year MACRS property. Its recovery period exceeds 20 years, so it is categorically ineligible for bonus depreciation. There is no exception, no planning around this rule, and no partial bonus for roofs.
This is one of the most common misunderstandings in commercial real estate tax planning. Taxpayers who hear that certain building improvements now qualify for bonus depreciation sometimes assume the rule applies broadly to any significant improvement — including a $500,000 roof replacement. It does not. Bonus depreciation is an inside-the-building provision for QIP; the building's exterior and structural components remain on the slow 39-year schedule.
Roofing in the context of a lease
When a tenant pays for roofing work on a leased building, the tax treatment depends on ownership and the nature of the work. In most commercial leases, the roof is the landlord's responsibility; if the tenant pays for roof repairs or a roof replacement as a lease obligation, the analysis shifts.
If the tenant makes a roofing capital expenditure on the landlord's building, the IRS may treat it as either: (1) additional rent expense to the tenant and income to the landlord, with the landlord depreciating the improvement; or (2) a capital expenditure by the tenant treated as an improvement to property the tenant does not own, in which case the tenant depreciates it over the remaining lease term or 39 years, whichever is shorter, under §168(i)(3). In either case, the tenant cannot claim QIP treatment or bonus depreciation for the roof work.
Worked numeric example
A retail property owner replaces the roof on a nonresidential commercial building in 2026 at a cost of $200,000. The property has been in service for several years. The owner's taxable income from active business operations (not passive) is $350,000.
Step 1 — QIP test: The roof is exterior. It fails the interior requirement. Not QIP.
Step 2 — Bonus depreciation eligibility: 39-year property. Not eligible. No bonus.
Step 3 — Section 179 analysis: The building is nonresidential real property. A roof is a listed §179(f)(1) category. The owner may elect §179 for up to the annual dollar limit on this roof. Assuming the §179 cap for the tax year is $1,220,000 (the 2024 amount; verify the current year limit) and no other §179 elections have been made, the owner can elect §179 for the full $200,000 roof cost in 2026. The $200,000 deduction is limited to $200,000 of the owner's taxable income — the owner has $350,000 so the limit is not binding.
Year-1 deduction with §179: $200,000
Remaining MACRS basis: $0 (fully expensed via §179)
Without §179 — straight-line 39 years, mid-month: If the roof was placed in service in July, the mid-month convention gives 5.5 months in year one: $200,000 ÷ 39 × (5.5/12) ≈ $2,350.
The §179 election accelerates $200,000 of deductions into year one instead of spreading $5,128 per year over 39 years, representing substantial present-value savings — assuming the taxpayer has the taxable income to absorb the deduction.
Practical planning considerations
Before replacing a commercial roof, consider:
Repair vs. capitalization. Under the tangible property regulations (Treas. Reg. §1.263(a)-3), not every roof expenditure must be capitalized. Routine maintenance, repairs to individual sections, and amounts that do not result in a betterment, restoration, or adaptation of the property may be deductible as repairs in the year incurred. A full tear-off and replacement almost certainly rises to the level of a capital improvement. Patching a small section may be deductible. Get the facts right before choosing a treatment.
Partial asset disposition. If the old roof was a separately tracked component of the building's depreciation schedule, you can claim a loss on the retirement of the old roof under Treas. Reg. §1.168(i)-8. This lets you write off any remaining undepreciated basis of the old roof in the year it is disposed of — a deduction separate from the cost of the new roof, and one that is often overlooked.
Section 179 interaction with passive activity rules. §179 is not available to passive activities. If the commercial building is a rental and the owner is a passive investor, §179 generally cannot be used for the roofing cost. Active business owners (materially participating) or those holding commercial property in an active trade or business can use §179.
Cost segregation and roofing components. A cost segregation study will not reclassify the primary roof structure as shorter-lived property, but it can separately identify insulation, rooftop HVAC equipment, skylights, and roof-mounted solar panels as personal property or other shorter-lived assets. Those components — not the roof deck and membrane itself — may qualify for shorter MACRS lives and potentially bonus depreciation.
Frequently asked questions
Can I claim bonus depreciation on a new commercial roof?
No. A roof is not QIP and does not have a recovery period of 20 years or fewer under MACRS GDS, so it is ineligible for bonus depreciation under §168(k). It is a 39-year structural component.
How long do I depreciate a commercial roof?
A roof on a nonresidential commercial building is a structural component depreciated over 39 years using the straight-line method and mid-month convention, unless you elect Section 179 to expense it (subject to the annual dollar cap and taxable income limit).
Can a roof on a commercial building qualify under Section 179?
Yes. The TCJA expanded Section 179 to include roofs on nonresidential real property as a category of qualified real property under §179(f)(1)(B). You can elect to expense the cost immediately, subject to the annual dollar limit and the taxable income limitation of §179.
What about a roof on a residential rental?
A roof on a residential rental building is a 27.5-year structural component. Section 179 does not apply to residential rental property. There is no bonus depreciation for 27.5-year property because that recovery period exceeds 20 years.
Educational information and estimates only. Not tax advice. Tax rules change and vary by situation; consult a qualified tax professional before acting.