There are several factors which enter into the problem of deter mining the most suitable pitch to give a roof, and they must be carefully considered before arriving at a decision. In the first place there is to be considered the appearance of the finished roof when the building is completed. In this connection it may be said that personal preference and individual taste on the part of the designer are the determining factors, and that no hard and fast rules can be laid down. Another thing which must be thought of is the relative cost of the different slopes or pitches, as this is often of great impor tance and, in the case of a large number of buildings, would make considerable difference in cost. It may be said that in general a roof with a comparatively low pitch, say about thirty degrees, corre sponding to a rise of approximately 68 inches per foot of run, is the most economical so far as the roof framing alone is concerned. Of course such a roof gives no accommodation in the attic portion of the building. Consideration must also be given to the question of the climate in which the proposed building is to be erected, as this will have a very decided influence upon the decision in regard to the most suitable pitch for the roof. In cold northern climates where
the snowfall is great, it is best to have a roof with a steep pitch, so that it will shed the snow and rain, or melted snow as quickly and as thoroughly as is possible. In a warm southern climate where there is no snow and where the rain fall is not large, a roof of smaller pitch may safely be used and will be more economical of construction. The character of the material to be used for covering the roof sur faces must also be remembered in determining the pitch, since if this roof covering is very impervious to water the roof may be given a lower pitch than if the roof covering is more easily penetrated by rain and snow. In general it may be said that roofs covered with slates may be safely given a pitch of from 5 to 51 inches to the foot run, while a roof covered with shingles must not be flatter than thirty degrees or nearly 7 inches to the foot run. Flat roofs should be covered with some preparation of tar and gravel, or with metal, tin, copper, galvanized iron, or zinc. Any roof which has a rise of less than 3 inches to the foot may be considered to be flat.