Hey Sivakumar

As per query you have not given details about your house i.e. size of the house, RCC columns, beams provided or not and thickness of the wall with their widths and depth of the foundation.
However when one constructs the house he takes generally 3 feet width of the foundation and 2.5 to 3 feet depth of the foundation from the ground level. You have constructed the ground floor earlier and if there is not any crack in the walls, you may construct first floor or second storey. It is better if possible you may check depth and width of the foundation or take necessary helps from the persons who are associated with construction work.

Thanks.