Partial asset dispositions: write off the old roof

By Tom, CPA · Updated October 27, 2026

Part of: Rental Property Taxes

TL;DR: When you replace a roof, HVAC system or other building component, the old one is usually still on your depreciation schedule. The partial asset disposition (PAD) election under Reg. 1.168(i)-8 lets you deduct its remaining basis as a loss in the year of replacement instead of depreciating a component you no longer own. You make the election by reporting the loss on a timely filed original return, including extensions.

Educational only, not tax, legal, or investment advice. Examples are illustrations, not predictions. Rules and limits change; verify current figures and talk to a qualified professional about your situation.

Your tenant pays the mortgage; the IRS pays for the roof (eventually, over 27.5 years). When you replace that roof in year 12, you start depreciating the new one over a fresh 27.5 years. But the old roof is still inside the building's basis, quietly depreciating. Without an election, you would be depreciating two roofs on one house.

The partial asset disposition rules, in Reg. 1.168(i)-8 and the tangible property regulations, fix that.

CPA Warning Label: Miss the PAD election on the original return and you generally keep depreciating a roof that is in a landfill for the rest of the 27.5 years.

What the election does

A building is generally one asset for depreciation. Under the disposition regulations, disposing of a structural component of a building (such as the roof) is not automatically a disposition. The partial disposition election lets you treat the retirement of a portion of an asset as a disposition, so you can:

• stop depreciating the retired component;
• deduct its remaining adjusted basis as a loss (generally an ordinary section 1231 loss, offset by any salvage or insurance proceeds);
• start depreciating the replacement on its own schedule.

The election applies to a portion of a building, a structural component, or a portion of a structural component, as long as you can determine the basis of the disposed portion.

Some partial dispositions are required, not elective, such as a sale of a portion of an asset or a disposition due to a casualty event. See rental casualty losses.

Why it matters beyond the deduction

Under Reg. 1.263(a)-3(k), if you take a loss on the disposition of a component (by PAD) and replace it, the replacement is a restoration that must be capitalized. That usually agrees with the roof case anyway. But it means you cannot take the PAD loss and also treat the replacement as a repair expense.

Calculating remaining basis

You need the original cost of the component you are retiring. Options under Reg. 1.168(i)-8(f):

• From records. If a cost segregation study or the purchase records separately state the roof's cost, use it.
• Producer Price Index (PPI) discounting. Take the replacement cost and discount it back to the placed-in-service year using the Producer Price Index for Final Demand (formerly Finished Goods) or another index the IRS designates. The regulations allow this method only when the replacement is a restoration, not a betterment or an adaptation to a new use, so a like-for-like roof qualifies but an upgrade to a fancier roof may not.
• Pro rata allocation (for multiple asset accounts or pools) based on the replacement cost of the disposed portion relative to the replacement cost of the whole asset.
• Cost segregation or engineering study done for this purpose.
• Other reasonable, consistently applied methods may be acceptable if they are supported by records; the regulations list the three above as examples.

Then subtract the depreciation allowed or allowable on that portion from its placed-in-service date to the date of disposition. The result is the remaining basis you deduct. Because a building component is depreciated over 27.5 years, the remaining basis can be large when a roof is replaced after 10 to 15 years.

Keep documentation of the method. An estimate based on a reasonable method and supporting data is much stronger than a guess.

Avoid double-depreciating

Without a PAD election:

• the old roof stays in the building's basis and keeps depreciating until the building is sold or fully depreciated;
• the new roof starts a new 27.5-year schedule;
• at sale, the leftover basis of the old roof reduces your gain, but only then.

So the old roof's cost is eventually recovered, but years later, and possibly at a disadvantageous rate. It reduces gain that may be taxed at 15% or 20% (or as unrecaptured section 1250 gain) instead of producing an ordinary deduction now.

With a PAD election:

• the building's basis is reduced by the old roof's original cost and the related accumulated depreciation;
• the remaining basis of the old roof is deducted in the year of replacement;
• the depreciation schedule for the building continues on the reduced basis.

Components that commonly qualify

• roofs;
• HVAC units, furnaces and water heaters treated as building components;
• windows and exterior doors replaced in a group;
• siding;
• a kitchen or bathroom removed in a remodel (cabinets, counters, fixtures);
• flooring other than carpet.

Carpet and appliances are usually separate 5-year assets already, so replacing them is an ordinary disposition of a whole asset. If they were fully depreciated or expensed with bonus depreciation, there is nothing left to write off.

When PAD is not worth it

If the remaining basis is small (for example, a component replaced near the end of its schedule, or an asset whose original cost cannot be estimated reasonably), the effort may outweigh the benefit. If the loss would only be suspended under the passive rules, the deduction still helps over time but not this year.

Working with your preparer

Tell your preparer about every major replacement in the year it happens, and give them the invoice and your estimate of the old component's cost. Many software packages need the original asset split into two lines: the retired portion (disposed) and the remaining building (continuing). Ask to see the updated depreciation schedule before the return is filed, because the election window closes with the original return.

Update the fixed asset list immediately, or the next preparer may keep depreciating the full original basis.

Timing

The election is made by reporting the gain or loss on the disposition on your timely filed original return, including extensions, for the year the disposed portion is retired (Reg. 1.168(i)-8(d)(2)). No separate statement is required. Generally:

• You generally cannot make it later on an amended return or with Form 3115, with limited exceptions in Reg. 1.168(i)-8(d)(2)(iv).
• Examples of the exceptions: when an IRS exam recharacterizes an amount you deducted as a repair into a capital improvement, a PAD election may be made for the disposed portion, and certain transition and method-change situations are covered. The details are narrow, so check the regulation or a tax pro before relying on one.
• The election cannot be revoked without IRS consent.

Practical steps the year you replace a component:

1. Get the cost of the new component on an itemized invoice.
2. Determine the original cost of the old component by one of the methods above.
3. Compute the allowed depreciation on it to date.
4. Report the loss on Form 4797 and adjust the depreciation schedule.

The election is especially valuable for landlords who own buildings a long time, because the old component's remaining basis is meaningful. It applies to rental property placed in service in any year. See real estate depreciation.

Example

Illustration: Fran bought a rental house in January 2012 for $300,000 with $240,000 allocated to the building. In June 2026 she replaces the roof for $24,000. No cost segregation was done. She uses PPI discounting: the PPI for Final Demand in 2012 was about 75% of the 2026 level (a hypothetical ratio for illustration only; look up the actual index values from the Bureau of Labor Statistics). Estimated 2012 cost of the old roof: $24,000 times 75% = $18,000.

• Accumulated depreciation on the old roof: 2012 placed in service in January (3.485%), plus 13 full years (2013 to 2025) at 3.636%, plus mid-month for June 2026. Roughly 3.485% + 47.27% + 1.67% = about 52.4%. $18,000 times 52.4% = about $9,430.
• Remaining basis: $18,000 minus $9,430 = about $8,570, deducted as a loss on Form 4797 in 2026.
• Building's depreciable basis going forward: $240,000 minus $18,000 = $222,000 (so annual depreciation on the original building drops by the old roof's share, about $655 a year).
• New roof: $24,000 over 27.5 years from June 2026.

Without the election, Fran would keep depreciating the old $18,000 roof until 2039. With it, she gets an $8,570 deduction now. At a 24% marginal rate, about $2,057 of tax value in 2026, subject to passive loss limits.

Recapture note: a PAD loss is generally a section 1231 loss, which is ordinary if your section 1231 items net to a loss for the year. At a later sale of the building, the retired roof is no longer part of it, so its basis and depreciation drop out of that sale's gain calculation.

Partial exclusion: for a former home rented out, see section 121 for rentals.