IAS-16 – Property, Plant and Equipment :

The cost of an item of property, plant and equipment should be recognised as an asset if, and only if, (a) it is probable that future economic benefits associated with the item will flow to the entity; and (b) the cost of the item can be measured reliably. An item of property, plant and equipment that qualifies for recognition, as an asset should shall be measured at its cost. An entity shall choose either the cost model or the revaluation model as its accounting policy and shall apply that policy to an entire class of property, plant and equipment. If an item of property, plant and equipment is revalued, the entire class of property, plant and equipment to which that asset belongs shall be revalued. If an asset’s carrying amount is increased as a result of revaluation, the increase shall be credited directly to equity under the heading of revaluation surplus. If an asset’s carrying amount is decreased as a result of revaluation, the decrease shall be recognized in profit or loss. However, the decrease shall be debited directly to equity under the heading revaluation surplus in respect of that asset.