I am not a tax professional, but I replaced a roof on a rental property and figured out how to do it. As others have noted, you must depreciate the new roof as a separate asset. But that is the easy part. You also need to remove the old roof from the value of the rental property, since you have been depreciating the building and roof as one combined asset up to the point you replaced the roof. From now on you will have two separate assets depreciating on their own schedules: the rental property building and the new roof. You need to calculate the value of the old roof when it was new or when you bought your rental property. You use the Consumer Price Index numbers (available online) to figure this value. Then you use TurboTax to sell/dispose the old roof, and manually reduce the remaining depreciation of the building on the appropriate TurboTax screen. The IRS actually has pretty good instructions on how to do this, please refer to <a rel="nofollow" target="_blank" href="
https://www.irs.gov/irb/2014-36_IRB#TD-9689">https://www.irs.gov/irb/2014-36_IRB#TD-9689</a>.
