Abstract: The present invention provides a door frame comprising of two piece units and the method of installment to provide connection between the casing and the frame with a self-alignment system. This is done by a tongue and groove connection and plurality of prefabricated dowels that are specially formed to engage the grooves provided in the frame through the entire attachment area of the frame units together. The door frame units are being assembled and secured together by providing a solid reinforced assembly. In the door frame system of the present invention a strong square joint can be produced by inserting dowels at critical joints which is significantly stronger fastening mechanism than other fastening means such as nails, staples, etc. Low expansion reinforced foam fills the cavities of the frame and creates a solid bond between door system and casing.