Additions made in an already depreciated asset

in my view it would be approprite to revalue the asset and also since the additions are made, it should be capitalized along with the revalued figure to be shown in the balance sheet

I think suggestion given by vivek is correct and in this AS-10 willbe followed

You need to consider, whether the estimated life of the asset has undergone any change. It is quite possible that the additions to existing plant might be to give it a new lease of life. In that eventuality, it would be appropriate to find out the new estimated life of the asset after the additions. Then the new additions alongwith the existing value can be depreciated over the estimated life of the asset. When deciding depreciation, Company Rates need to be kept as minimum base.