CHAPTER V. 

 ROOFS. 



General Roofs in mill construction buildings are usu- 



Construction ally flat with a slight pitch of ^ i ncn to % 

 inch to the foot. They are framed in the same 

 manner as are the floors, the under side of the roof forming 

 the ceiling for the top story. If a plastered ceiling is neces- 

 sary, the metal lath which is to hold the plaster should be fitted 

 around the girders and against the roof boards in such a man- 

 ner as to leave no spaces between the plaster and wood. If 

 plastering is to be used in contact with the timber, it should 

 be of plain lime mortar without the skim coat of lime putty. 

 The rough plaster is sufficiently porous to permit seasoning to 

 continue if necessary. 



Roofs should be covered with an incombustible material. 

 Composition, slag or gravel roofing is used to a large extent 

 for this purpose. 



Flashing^ Roofing^ ^ The necessity of a cor- 



nice is questionable, even 

 from an architectural 

 standpoint. It is a con- 

 stant source of expense 

 for maintenance and is 

 likely sooner or later to 

 become dangerous and 

 fall without warning, 

 due to the failure of 

 concealed members. Pro- 

 viding a cornice is to be used, the open wood type shown in 

 Fig. 13 is recommended by the Associated Factory Mutual 

 Fire Insurance Companies, but an incombustible cornice is 

 advisable when there is exposure from neighboring buildings. 



Girders While the size of the girders to support the roof 



and Roof will not need to be as large as those for supporting 



the floors on account of the lighter loads carried, 



the minimum sizes of material permitted will control the size 



(^ Cast Iron 

 Wall Plate 



Roof 

 Anchor 



Fig. 13. Detail of Wood Cornice. 



Page thirty-one 



