Also known asabujh muhuratsaade teen muhuratswayam siddh
Vastu poojan is done not only at the start of construction but at several stages and family events; at griha arambh and griha pravesh it is essential.
The whole house, with an offering at every devta pad
No. Do it at bhoomi poojan or shilanyas, when the first slab is laid, when the main door frame is installed and on griha pravesh; the start of construction and griha pravesh are essential. Also do it after a renovation in which walls are broken, for a marriage, the start of a job or business and the birth of a child, and once a year on a swayam siddh muhurta such as Akha Teej or Gudi Padwa for a year of happiness and peace.