The inclination of the slopes of iron roofs should, as in wooden roofs, depend upon the nature of the covering to be used.

With slates (the only covering at present under consideration) the pitch may vary, according to the size of the slates, and the climate, as stated at p. 207.

The steepest pitch there mentioned is, however, very seldom used for iron roofs, and in many cases where such roofs are erected - over railway stations, sheds, or other places where a slight leak is not of much importance - the slope is for economy made rather flat, 21° or 22° being a very common pitch for roofs covered with ordinary slating. Large slates are of course to be preferred for these flatter roofs, and "Duchesses" are very often used for the purpose.