The paper considers the saddle shape cable roof, which is formed by two orthogonal groups of cables, joined with tensioned cables. The kinematic invariability of the roof obtained by prestressing of the cables, enables to refuse from the hard ferroconcrete slabs in the construction of the cable roof and use light composite materials. The main rational geometrical characteristics were ascertained by a numeral experiment for a square in plane saddle shape cable roof, which is supported by the tensioned cables by taking into account the weight of cable net per the covered area.