The roof areas multiplied by the roof load per square foot will give the joint loads.

## Example 5

What roof loads should we use in determining the stresses for the trusses Figs. 249 and 250?

Ans. - The dead weight per square foot would be about as follows, assuming that the roof is to be covered with slate, 3-16-in. thick:

 For slate...................... 7 1/4 lbs. For sheathing................. 3 " For rafters.................... 3 " For purlins................. 2 " For truss (Table VII.) 3 1/4 " Total dead weight............... 18 1/2 lbs.

For the wind and snow combined, we should allow by Table X. 27 1/2 lbs., the pitch of the roof being a mean between 450 and a 1/3 pitch. Therefore the roof load per square foot should be taken at 46 lbs. The roof areas supported at the joints were found in Example 1, to be as follows:

For truss 1, area at joint 2, = 93 1/2 sq. ft.; and at joint 3, 100 sq. ft. For truss 2, area at joint 2, = 118 sq. ft., and at joint 3, 128 1/2 sq. ft. For truss 3, area at joint 2, = 124 2/3 sq. ft., and at joint 3, 135 2/3 sq. ft. Multiplying these areas by 46, we obtain the following loads:

 For truss 1, at joint 2, 4,301 lbs.; at joint 3, 4,600 lbs. For truss 2, at joint 2, 5428 lbs.; at joint 3, 5,911 " For truss 3, at joint 2, 5,734. lbs.: at joint 3. 6.240 "

## Example 6

Estimate the joint loads for the truss shown by Fig. 253, the roof being shingled on 7/8-in. sheathing nailed to 2x4 rafters.