What is standard % error for the construction industry for the length of something i.e. beam?
Actually, there are standards. They aren’t always a percentage, though. Tolerances for concrete construction (depth of rebar, width of beams, etc.) are covered in ACI 318 in the US. Tolerances for steel construction are covered in ASTM A6, I believe, but at any rate most are listed in the AISC steel construction manual or the code of standard practice for buildings. The manual also discusses tolerances for anchor bolt placement, base plate levelness requirements, column tolerances for out of straightness, out of level, as well as tolerances on specified camber. An example: Camber for beams < 50' long, -0/+1/2" meaning the camber specified on the drawing or up to 1/2" more than that specified on the drawings, but not less than the camber shown on the drawings. Beam underrun/overrun I believe is at most 1/4", which is why a lot of the AISC MSC tables for connections show (reduced by 1/4" for beam overrun) on the footnotes. There are also standards on how they are measured and when they a
