Span Rules of Thumb

Question 1

Metal decking

Answer 1

Spans 1.5’ - 16’ (depends on pan depth/type)

depth = span/24

Question 2

Light gauge steel joists

Answer 2

Spans 10’ - 26’

depth = span/20

Question 3

Precast concrete: solid flat slab & hollow core slab

Answer 3

Spans 12’ - 24’ / 12’ - 40’

depth = span/40

Question 4

Precast concrete: single tee

Answer 4

Spans 30’ - 120’

depth = span/30

Question 5

Precast concrete: double tee

Answer 5

Spans 30’ - 100’

depth = span/28

Question 6

Precast concrete: rectangular, l-shaped, inverted tee beams

Answer 6

Spans 15’ - 75’

depth = span/15

Question 7

Concrete slab: one-way

Answer 7

Spans 6’ - 8’

depth = span / 30

Question 8

Concrete slab: one-way joist

Answer 8

Spans 15’ - 36’

depth = span/24

Question 9

Concrete slab: two-way with beam

Answer 9

Spans 15’ - 40’

depth = perimeter/180

Question 10

Concrete slab: two-way waffle

Answer 10

Spans 24’ - 54’

depth = span/24

Question 11

Concrete slab: two-way flat plate

Answer 11

Spans 12’ - 24’

depth = span/33

Question 12

Concrete slab: two-way flat slab

Answer 12

Spans 20’ - 40’

depth = span/36

Question 13

Concrete beam cast into slab

Answer 13

depth = span/16

Question 14

Wood dimension lumber joists

Answer 14

2x6: spans 0’ - 10’
2x8: spans 8’ - 12’
2x10: spans 10’ - 14’
2x12: spans 12’ - 18’
depth = span/16

Question 15

Prefab wood joists & trusses

Answer 15

I joist: spans 20’ - 60’
Truss: 40’ - 60’
Steel webbed: 60’ - 100’
depth = span/18