Gst on builders

GST has been fixed at 12% for under construction and new projects. A lot of raw materials like cement and steel have been fixed at a 28% taxation rate.  Houses will be at little lower prices then before because of gst as cascading effect shall be removed and there will be less tax burden on the consumer.

How are GST apply on under construction property?? and How can input credit of TAX are awailed which pay before the GST??