Land is not depreciated, but the purchase contract does not split the cost between the cost of the land and the cost of the building. The useful life of the building is likely to be long, so estimating it is going to be very difficult. The residual value at the end of the useful life is virtually impossible to estimate. Who knows how much it will be in say 50 years time. Commercial buildings tend to be different from each other, whereas residential buildings are somewhat similar. The building concerned is a commercial, freehold building, not held for investment purposes. So how do I calculate, and justify, the depreciation of a commercial building?