The said county commissioners and corporate authorities shall adopt plans and specifications for the erection of such hospital building or buildings as may be deemed necessary. Upon approval of such plans and specifications by the court of common pleas of the proper county, the county commissioners and corporate authorities are authorized to erect upon such site the building or buildings according to the plans and specifications so adopted and approved. If any lands purchased or condemned have erected thereon any buildings suitable for the purposes provided for by this act, the county commissioners and corporate authorities are authorized to use such buildings and to make such repairs and alterations thereto as may be necessary.