## Example 7

What joint loads should be used for the truss shown by Fig. 252, assuming that the sloping roof is to be covered with slate and the deck roof with tin, and that the building is located in one of the central states?

Ans. - The weight per sq. ft. of the sloping roof will be

 For slate....................... 7 1/4 lbs. For sheathing................ 3 " For 2 x 6 rafters..................... 2 1/4 " For purlins................ 2 " For truss, 64' span..................... 4 " Wind and snow........................ 30 " Total..................... 48 1/2 lbs.
 For the deck roof: Tin.................... 1 lb. Sheathing rafters and purlins................... 6 1/2 lbs. Truss........................ 5 1/4 " Snow.................... 30 " Total............................... 42 1/2 lbs.

Multiplying the roof areas supported at the joints, as found in Example 2 by these loads, we have

 Load at joint 2. . = 118 sq. ft. x 48 1/2 lbs. = 5,723 lbs. Load at joint 3. . = 59 sq. ft. x 48 1/2 lbs = 2.862 =5,667 lbs. 66 sq. ft. x 42 1/2 lbs. = 2,805 Load at joint 5. . = 111 sq. ft. x 42 1/2 lbs. = 4,718 lbs. Load at joint 7. . = 114 sq. ft. X 42 1/2 lbs. = 4,845 lbs.

## Example 8

What load per sq. ft. should be taken in computing the stresses in a truss of 64-ft. span supporting a flat roof in the New England states, the rafters to be 2" x 8", 16" on centres, resting directly on the trusses, and the roofing to be 5-ply tar and gravel?

Ans. - The weight per square foot should be estimated as follows:

 Roofing....................... 6 lbs. Sheathing.................... 3 " Rafters...................... 3 " Truss................. 5 " Snow......................... 40 " Total....................... 57 lbs.