Ducts or Pipes through Steel Joists - Maximum Sizes

Maximum sizes of ducts or pipes through K series joists. K series are common open web joists, standard sized for typical applications. K types span from 8' to 60' across with depths of 8" to 30".

Joists Depth (in)	Round Duct Size (in)	Square Duct Size (in)	Rectangular Duct Size (in)
8	5	4 x 4	3 x 8
10	6	5 x 5	3 x 8
12	7	6 x 6	4 x 9
14	8	6 x 6	4 x 9
16	9	7 x 7	6 x 10
18	11	8 x 8	7 x 11
20	11	9 x 9	7 x 12
22	12	9 x 9	8 x 12
24	13	10 x 10	8 x 13