According to vastu principles pooja room should be in north -east direction because pooja room north quadrant provides good result. Don't place or construct pooja room in bed room and above, below or near toilet. Don't construct pooja room on floor other then ground floor and below stairs.
Doors and windows of pooja room must be placed on north or east. Doors must have two shutters. There should be big ventilator for so holy smoke can be exhausted easily. Walls should be painted in white, light yellow or light blue color where flooring can be done of white or off-white marble.
Idols of God should be kept in north-east portion of pooja room without facing each other and door of pooja room. Kalash or Water body must be kept in north or east of pooja room. Agni kund in south-east.
The room should not be used for other purposes like storage or other room.