The architectural differences between Northern and Middle-Southern Vietnam are based on the method for the roof pitch planning. The Northern method is based on the horizon, vertical line and the dimensional unit, the roof line is designed by the horizontal dimension and the height. The Middle-Southern method is not based on the horizon, vertical lines, the plan designed by concrete dimensions, and the roof line fixes one hypotenuse unit as 2 height units. The points are namely the difference of the main design tools, the square tool and the equilateral triangle tool, those can be considered as a gap of the traditional architectural technique and culture between two regions.
