Elevation datum

[heals88]

I have a skid with an I beam and 1/4" checker plate on top.
Would you take the 0 elevation as the top of the I beam or top of checkerplate? I prefer top of checkerplate but others say top of beam is industry standard, is that true?

 

[mk3223]

IMO, it can be called out either way.
Use 0.00 at top of I beam if only portion of the I beam area is covered by the plate. Otherwise, use 0.00 at the plate surface as it covers on the whole I beam structure. Either way, it should be clearly noted on the drawing for clarity.