standard joists

Longspan and Deep Longspan Steel Joists can be furnished
with either under-slung or square ends, with parallel chords
or with single or double pitched top chords to provide sufficient
slope for roof drainage. Square end joists are primarily
intended for bottom chord bearing.
Sloped parallel-chord joists shall use span as defined by the
length along the slope. The joist designation is determined
by its nominal depth at the center of the span and by the
chord size designation.
The depth of the bearing seat at the ends of underslung LHand
DLH-Series Longspan Joists has been established at 5
inches (127 mm) for chord section number 2 through 17. A
bearing seat depth of 7 1/2 inches (191 mm) has been established
for the DLH Series chord section number 18 and 19.



JOIST ROUND SQUARE RECTANGLE
DEPTH
8 INCHES 5 INCHES 4x4 INCHES 3x6 INCHES
10 INCHES 5 INCHES 4x4 INCHES 3x7 INCHES
12 INCHES 7 INCHES 5x5 INCHES 3x8 INCHES
14 INCHES 8 INCHES 6x6 INCHES 5x9 INCHES
16 INCHES 8 INCHES 6x6 INCHES 5x9 INCHES
18 INCHES 9 INCHES 7x7 INCHES 5x9 INCHES
20 INCHES 10 INCHES 8x8 INCHES 6x11 INCHES
22 INCHES 10 INCHES 9x9 INCHES 7x11 INCHES
24 INCHES 12 INCHES 10x10 INCHES 7x13 INCHES
26 INCHES 15 INCHES* 12x12 INCHES* 9x18 INCHES*
28 INCHES 16 INCHES* 13x13 INCHES* 9x18 INCHES*
30 INCHES 17 INCHES* 14x14 INCHES* 10x18 INCHES




i found this in: http://www.quincyjoist.com/files/SJI/intro.pdf