Sweat Shop Drawings

January 29, 2009

The largest project of my career has recently started construction.  Upon completion, the structure will be the tallest building in Cincinnati.  It will be an icon of the city’s skyline, featuring an exposed steel tiara inspired by Princess Diana.  It’s pretty exciting to tell people about my role in this exciting project.

Learn more about the construction progress at: http://news.cincinnati.com/article/20090119/NEWS01/901190345/1055/NEWS

However, big projects mean big stacks of shop drawings for the design engineers to review.  Shop drawings are detailed drawings that indicate precisely how each individual piece of the structure is to be fabricated.  They are drawn by meticulous engineers that work closely with steel fabricators, rebar suppliers, and other structural element producers.  Producing quality shop drawings ensures that every piece of the structure shows up at the job site sized and detailed to fit together.

On the other hand, structural design engineers, like me, put together drawings that give only the general specifications for each piece.  Our plans typically represent beams only as single lines on paper.  The detailers and fabricators have to interpret those lines and create actual 3-dimensional beams.  That’s where the shop drawings come in.  Before they actually start cutting the steel, the shop drawings are sent to the structural design engineer for approval.  This places quite a lot of pressure on the design engineer, because failing to review and return the shop drawings in a timely fashion can delay the project.

Reviewing shop drawings is a tedious and time-consuming task.  Each sheet is packed full of information.  During the initial design phase, the shape and size a steel beam itself is the main concern.  Steel shop drawings, however, must include much more information including: the number of bolts at each connection, the size of welds, the thickness of the gusset plates, the camber (upward bend), coping (cutting back a portion of the flanges to fit two beams together), location of bent plate pour stops, and much more.  Concrete rebar shop drawings are just as complex, because each bar, with all its bends and hooks, must be accounted for.

If mistakes are found, the reviewer has two options.  For small mistakes, the drawing can be approved as noted. This means the fabricator can review the comments marked on the sheet by the reviewer and proceed right away.  However, when errors are found that could have a serious impact on the structure, the reviewer would ask that the drawing be revised and resubmit.  This prevents the fabricator from working on the piece until the reviewer approves the corrected drawing.

Digesting all of the information on the shop drawing and correcting mistakes can take a long time.  Usually, I’ll find a rhythm after working through the first couple of pages.  Still, I find that I have to stop and take a break at least once an hour, so that I can maintain my focus.  For the past several weeks, I’ve been contributing about 20 hours per week to the mountain of shop drawings.  We have more people working on the project now than at any other time in the life cycle of the project.  That’s pretty typical for large projects.

As a design engineer, I don’t literally contribute any blood, sweat or tears to the building.  I think reviewing shop drawings is the greatest test of fortitude that I’m asked to partake during the project, which isn’t too much to ask.  The upside of carefully reviewing the shop drawings is that I do feel more intimately connected to the building.  Having literally reviewed the nuts and bolts of the structure, I’ll have a unique perspective of the structure.

  • Could your project have benefited by having structural steel shop drawings that were prepared during the design phase? This seems to be a growing trend for many reasons

    1) Fewer RFI’s as detailer works with A/E as project is designed
    2) Less time is wasted for contractor’s project manager who no longer has to funnel questions from a fabricators detailer up to the architect or engineer only to have the answer funnel back downstream the way
    3) Tighter pricing by steel fabricators/erectors who are now pricing against shop drawings and not design drawings
    4) Steel detailing and the mill order can now be taken out of the project’s critical path

    Lower cost, tighter schedule. So what is the downside of all this? I’m sure there are some but so far I can’t think of any….

  • hi,
    i’ve just found your blog, thanks for usefull informations.
    best wishes.

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