2014 I added a building as a business asset and was taking depuration on the amount in 2018 I paid it off the building add that amount to what is the best way

[Anita01]

Paying off a mortgage on a building does not change anything about depreciation.  The building still has the same original cost, the same amount spent on improvements.  It continues to be depreciated for the same number of years.  You don't add anything for paying off a mortgage.