Reduction in the value of a building ( the construction part only) over a passage of time is property depreciation. Depreciation rates are prescribed in the Income Tax Act to calculate depreciation deductible from the Total Income. Depreciation under Income Tax can be claimed only by assesses who has Income From Business/Profession. The rate of property depreciation rages in between 5 - 10 % per year for a residential building. http://taxindia.pz10.com/2013/08/depreciation-rates-under-income-tax-act.html
This property depreciation has nothings to do with the selling price of the property. In the last few decades the property prices over the globe have only increased irrespective of the age of the property. Property prices are majorly govern by the "Demand and supply gap"