Flat Arch
A flat arch has commonly the angle created through skewbacks as 60o with horizontal, therefore forming an equilateral triangle along with intrados as the base. The intrados is apparently flat, but it is provided a slight rise of camber of about 10 to 15 mm per meter width of opening to permit for small settlements. Therefore, the extrados is remaining horizontal and flat. Flat arches are used only for light loads, and for spans up to 1.5 m. The depth of the arch is commonly kept equal to three or four courses of the brick.