Structural Material Waste

When inputting project material quantities in EC3 or other tools, how do you typically estimate/address construction waste, if at all?

Of particular interest to me:

  • Concrete volume - if a concrete pour is in theory X yd^3, in reality Y% more is sent to the site. How much more? Is there any guidance or research on industry averages by element type (foundations/slabs/walls/etc)?
  • Rebar - we can estimate with reasonable accuracy the theoretical quantity of rebar including laps and hooks. It’s more difficult to estimate carry bars since we don’t directly specify those, and some miscellaneous bar on site is bound to end up as true scrap. How can this extra bar be estimated? Is it even worth attempting this, or is it essentially a rounding error?

It is my understanding that waste generated during the production/fabrication process is generally included as part of the product specific or industry EPD, but to account for extra material supplied, as in the examples above, one would need to include that in the EC3 material quantities input (please correct me if wrong on that). Is it common practice to include any allowance for waste? I am new to this process and would welcome any thoughts or links to resources on the subject!