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As staircase is very important in vastu as one goes up and comes down with this if placed properly as per vastu principles then it will take you up in life and it placed in wrong direction then it will bring you down
If you want to make internal store then you can Construct staircase in South-West corner or West or South directions in a home.
If you are planning to construct external staircase then you can construct external staircase in South-East facing East, South-West facing West, North-West facing North and South-West facing South.
Also the staircase should be clockwise as far as possible