Straight stairs : Despite its simplicity, it is convenient and functional. It is easy to go up and down it, as also to carry things on the next floor. But the presence of one long flight makes this type of staircases limited in height. As you already know, the amount of treads in one straight flight shall not exceed 16. The usage of staircases with straight flight is feasible only in those cases when we need to join two levels connected by imaginary straight line.