Frequently Asked QuestionsShow All
Q: What thickness and size of washer is required for the preferred hole diameters in base plates?
A: Hole sizes in base plate may be up to 6 mm larger than the anchor bolt diameter (NZS 3404, Clause 18.104.22.168.2). Holes would normally be drilled. Holes require a special plate washer of 4 mm minimum thickness under the nut if the bolt hole is more than 3 mm larger than the anchor bolt diameter. The oversize holes will accommodate reasonable misalignment in the location of the anchor bolts and allow adjustment of column bases to meet the tolerance requirements between column centres permitted in NZS 3404. Recommended diameter of bolt holes, minimum washer dimensions and thickness are given in the table below.
For further guidance refer to:
 Hogan, T.J., Design Guide 7 Pinned base plate connections for columns, Australian Steel Institute, 2011
 Fisher, J.M. and Kloiber, L.W., Base plate and anchor rod design 2nd Edition, AISC Design Guide 1, American Institute of Steel Construction, 2010
Table 1: Recommended Sizes of Anchor Bolt Holes and Washers in Base Plates (after Ref 2 and reproduced in Ref 1]