MILL CONSTRUCTION BUILDINGS 



Trussed In many types of commercial buildings open spaces 

 Roofs without posts are desired. This condition is very 

 likely to exist in manufacturing plants where large 

 areas of clear floor are necessary for the movement of machin- 

 ery or assembling machine parts. In such buildings the 

 posts are taken out and roof trusses used to span the opening. 

 Trusses are ordinarily placed from 8 feet to 20 feet on centers 

 with 3-inch plank spanning the distance between the trusses 

 as in standard mill roofs, or resting on purlins spaced not less 

 than 8 feet on centers and running from truss to truss. It is 

 advisable to have the purlins supported at the joints of the 

 trusses to prevent bending in the members of the top chord. 

 Other details of the roof are similar to those described above. 



Saw-Tooth Where a saw-tooth form of roof is needed, the 



Roofs roof planks are supported by heavy timber 



beams, or by steel trusses, spaced from 8 feet to 



10 feet on centers, and in turn carried by timber girders, trusses, 



or columns. In fact, 

 the design of the roof 

 planking itself varies 

 but little from that 

 used in the ordinary 

 flat roof of standard 

 mill construction. The 

 detail of the support- 

 ing members will vary 

 with the type used. 

 Figs. 14 and 15 show 

 two forms of saw-tooth 

 roofs, one wholly of 

 timber construction 

 and the other of timber 



PI.. 16. Detail of Valley. ^ ^ Rg ^ 



shows a detail of the valley used in timber construction, such 

 as shown in Fig. 14. These details are as recommended by the 

 Boston Manufacturers Mutual Fire Insurance Company. 



Page thirty-five- 



