Staff Memo: What should my reference points be on my drawings (Detailing Tips)

See the image below: there is a very serious potential issue here. Can you spot it?

If you want to see a live link – please click here:

What’s the problem?

Our steel is tied into concrete.

What’s wrong with steel on concrete?

• The problem is that concrete is almost never poured correctly. It is never correct.
• If your dimension and cut beams to concrete as a reference point, that means all your dimensions will be wrong – because the concrete is NEVER where you expect it to me.
• What should you do?

1. People agree to work to grid lines as reference points. You must dimension to gridlines – unless this is not applicable.
2. Gridlines are typically not applicable when your steel ties into another structure (e.g. steel or to concrete). If it does, as in this case:
3. Get a site measurement of where the existing structure is: and use that as a reference.
4. But what you must never do is to dimension to an arbitrary structure without a site measurement.

What happened in this case?

• In this case there was something already installed up against the concrete. So we must dimension everything to what is actually installed.

What happens if I dimension to concrete?

• This means that your beams will not fit on site.
• Which means you’ll get a very angry client: you will cost your client time and money.
• This means your name and reputation will go down: clients will not want to deal with both you and our firm.

Summary:

What should I do?

• Always make references to GRID LINES, not concrete or steel UNLESS you have a site measurement.
• Never dimension to something upon which you do not know the location.