a. Dead Load. A buildings structure weight is called the dead load. The dead load per square foot of floor area is carried directly or indirectly to the girder by bearing partitions. Dead load varies according to the method of construction and the building height. The structural parts included in the dead bad are--

• Floor joists for all floor levels.
• Flooring materials, including the attic if it is floored.
• Bearing partitions.
• Attic partitions.
• Attic joists for the top floor.
• Ceiling lath and plaster, including the basement ceiling if it is plastered.

b. Total Dead Load. For a building of light fame construction similar to an ordinary frame house, the dead-load allowance per square foot of all structural parts must be added together to determine the total dead load. The allowance for an average subfloor, finished floor, and joist without basement plaster should be 10 pounds per square foot. If the basement ceiling is plastered, an additional 10 pounds per square foot should be allowed. If the attic is unfloored, a load allowance of 20 pounds must be made for ceiling plaster and joists when girders or bearing partitions support the first-floor partition. If the attic is floored and used for storage, an additional 10 pounds per square foot should be allowed.

c. Live Load. The weight of furniture, persons, and other movable loads, not actually a par of the building but still carried by the girder, is called the live load. The live load per square foot will vary according to the use of the building and local weather conditions. Snow on the roof is considered part of the live load. The allowance for the live load on the floors used for living purposes is usually 30 pounds per square foot. If the attic is floored and used for light storage, an additional 20 pounds per square foot should be allowed. The allowance per square foot for live loads is usually governed by local building specifications and regulations.

d. Load Per Linear Foot. When the total load per square foot of floor area is known, the load per linear foot on the girder can easily be figured. Assume that the girder load area of the building shown in Figure 1-12 is sliced into 1-foot lengths across the girder. Each slice represents the weight supported by 1 foot of the girder. If the slice is divided into 1-foot units, each unit will represent 1 square foot of the total floor area. The load per linear foot of a girder is determined by multiplying the number of units, 12, by the total load per square foot, 70 pounds. This gives you 840 pounds per linear foot on the girder (12 x 70 = 840 pounds). Now you can take the 840 pounds per load per linear foot of girder and use Table 1-1 to determine the girder size. If your number is not on the table, round up.

e. Total Floor Load. Note in Figure 1-12 that the girder is off center. Remember that half of the load is supported by the girder and half is supported by the foundation walls. Therefore, the joist length to be supported on one side of the girder is 7 feet (half of 14 feet), and the other side is 5 feet (half of 10 feet) for a total distance of 12 feet across the load area. Since each slice is 1 foot wide, it has a total floor area of 12 square feet. Assume that the total floor load for each square foot is 70 pounds. Multiply the length times the width (7 feet x 12 feet) to get the total square feet supported by the girder (7 feet x 12 feet = 84 square feet).