Span Rules of Thumb Flashcards
Metal decking
Spans 1.5’ - 16’ (depends on pan depth/type)
depth = span/24
Light gauge steel joists
Spans 10’ - 26’
depth = span/20
Precast concrete: solid flat slab & hollow core slab
Spans 12’ - 24’ / 12’ - 40’
depth = span/40
Precast concrete: single tee
Spans 30’ - 120’
depth = span/30
Precast concrete: double tee
Spans 30’ - 100’
depth = span/28
Precast concrete: rectangular, l-shaped, inverted tee beams
Spans 15’ - 75’
depth = span/15
Concrete slab: one-way
Spans 6’ - 8’
depth = span / 30
Concrete slab: one-way joist
Spans 15’ - 36’
depth = span/24
Concrete slab: two-way with beam
Spans 15’ - 40’
depth = perimeter/180
Concrete slab: two-way waffle
Spans 24’ - 54’
depth = span/24
Concrete slab: two-way flat plate
Spans 12’ - 24’
depth = span/33
Concrete slab: two-way flat slab
Spans 20’ - 40’
depth = span/36
Concrete beam cast into slab
depth = span/16
Wood dimension lumber joists
2x6: spans 0’ - 10’
2x8: spans 8’ - 12’
2x10: spans 10’ - 14’
2x12: spans 12’ - 18’
depth = span/16
Prefab wood joists & trusses
I joist: spans 20’ - 60’
Truss: 40’ - 60’
Steel webbed: 60’ - 100’
depth = span/18