One of the outside men is supporting half of the 8-foot plank, or 20 pounds. The man on the opposite
outside end is supporting half of the 12-foot plank, or 30 pounds. The man in the center is supporting
one half of each plank, or a total of 50 pounds. This is the same total weight he was lifting before. It is
important to remember that a girder carries the weight of the floor on each side to the midpoint of the
joists which rest upon it.
1-6. Floor Load. After the girder load area is known, the total floor load per square foot must be
determined for safety purposes. Both dead and live loads must be considered.
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.
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
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.