Table II. Weight Of Floors, Partitions, And Roofs

Material.

Weight. Lb. per Sq. Ft.

Floors, including weight of beams -

Wooden, in dwellings......................................

10-15

Wooden, office buildings................................

25-30

Hollow-tile arch...............................................

70-90

Brick and concrete (broken stone) ................

100-130

Partitions -

Wooden ...........................................................

15-20

Hollow tile........................................................

15-30

Roofs, including framing -

Shingle .............................................................

6-10

Tin ...................................................................

6-8

Slate...................................................................

12-15

Tar and gravel..................................................

10-12

Corrugated iron

8-10

Tile ...................................................................

20-30

Note

If roofs are plastered underneath, add 6 pounds per square foot to the weight given.

In calculating the dead loads, there are certain weights which must be assumed. For instance, the weight of the floorbeams and girders are not known, because their size has not as yet been determined; likewise, the dimensions of the columns and many other structural details are unknown. The assumed weights are obtained by approximating the dimensions of the parts of the structure and estimating their weights. After the structure has been designed, the actual dead loads should be checked, to make sure they approxi mate closely to those assumed. If any considerable variation is found, it can be taken care of by increasing or diminishing the sizes already determined.

Weight of Fireproof Floors - In figuring the dead load for any system of floor construction, it is necessary to carefully calculate the total weight of the elements composing the system, which are the arches, filling, flooring, ceiling, and the steel construction. The weight of fixed or permanent partitions should always he taken into account, and the beams, etc. carrying them, proportioned accordingly. Where the partitions are movable, an additional weight of, say, 20 lb. per sq. ft., should be added to the dead load on the entire floor area. The finished floor line is usually considered as being 3 in. above the top of the I beams, and the ceiling line as 2 in. below the bottom of them. Cinder concrete filling, which is the usual backing for fireproof arch construction, averages in weight, when dry, 72 lb. per cu. ft., but is sometimes assumed to weigh only 48 lb. per cu. ft.

The weight of the various systems of fireproof floors vary from 60 lb. to 125 lb. per sq. ft. of floor surface, including the steel used; generally, however, a load of 80 lb. per sq. ft. will be sufficient for all economical fireproof floors.