A portion of my fence was damaged in the hurricane. How do you figure fair market value?

[CathiM]

Assuming this is for your personal-use residential real property, there are 5 methods you can use, method 4 & 5 only if you are in a federally declared disaster area. Your fence is considered an improvement to your real property.

For more details, see Rev. Proc. 2018-08.  

Here are the five methods. Personal-use residential real property generally is real property, including improvements, that is owned by an individual who suffered a casualty loss and that contains at least one personal residence.

1. The estimated repair cost safe harbor method allows you to figure the decrease in the FMV of your personal-use residential real property using the lesser of two repair estimates prepared by separate and independent licensed contractors. The estimates must detail the itemized costs to restore your property to its condition immediately before the casualty. The estimated repair cost safe harbor method is limited to casualty losses of $20,000 or less before the application of the limits under IRC § 165(h).
2. The de minimis safe harbor method allows you to figure the decrease in the FMV of your personal-use residential real property based on a written good faith estimate of the cost of repairs required to restore your property to its condition immediately before the casualty. The de minimis safe harbor method is available for casualty losses of $5,000 or less before the application of the limits under IRC § 165(h).
3. The insurance safe harbor method allows you to figure the decrease in the FMV of your personal-use residential real property based upon the estimated loss in reports prepared by your homeowners’ or flood insurance company. These reports must set forth the estimated loss you sustained from the damage to or the destruction of your property.
4. If the loss occurred in a disaster area and was due to a federally declared disaster then you may use the contractor safe harbor method or the disaster loan appraisal method. Under the contractor safe harbor method, you may use the contract price for the repairs specified in a contract prepared by an independent and licensed contractor to determine the decrease in the FMV of your personal-use residential real property. This safe harbor method does not apply unless you are subject to a binding contract signed by you and the contractor setting forth the itemized costs to restore your personal-use residential real property to its condition immediately before the casualty. 
5. Under the disaster loan appraisal safe harbor method, you may use an appraisal prepared to obtain a loan of federal funds or a loan guarantee from the federal government that identifies your estimated loss from a federally declared disaster to determine the decrease in the FMV of your personal-use residential real property.