Why Fabricators Join the Design Team on an Unusual Building

By Michael Stern, JDS Development Group

An industrial lathe and loose steel shavings on the floor of a metal fabrication shop where building components are cut.

The question comes up on almost every building with few precedents, and it almost always comes from an architect. Why is the fabricator sitting in this meeting when the drawings are not finished? It is a fair question, and the answer decides whether the detail on the page can be built at all.

The knowledge of what can actually be made sits in the shop that will make it, and it has to arrive while the drawing can still change. This is for architects, structural engineers and development teams deciding whether to bring a trade contractor into design, and how early.

What does design assist mean on a building with few precedents?

Design assist brings the company that will fabricate a system into the design phase, working under the design team, to test whether a detail can be made. The drawings remain the architect's and the engineer's.

The shop is there to answer a narrow question. Can this joint be cut, welded, shipped and hung in the sequence the drawing implies, to the tolerances the engineer wants? On an ordinary building nobody has to ask.

Standard assemblies have been built a thousand times, the shops know them, and the drawing set can be finished in peace before anyone prices it. That comfort disappears the moment the building stops resembling other buildings.

The buildable detail lives in the shop

A building with few precedents carries assemblies that no catalogue sells. The twin towers of The American Copper Buildings are joined 300 feet up by a three story skybridge, the first skybridge in New York City in 80 years. Nothing about a move like that sits on a shelf.

When a system is that unusual the work splits in a particular way. The structural engineer writes what the connection has to do and the fabricator's own engineer draws the piece that does it. That split is ordinary on facades, long span steel and glazing, and it is why the shop has to understand the intent before the intent is frozen.

What the shop brings is unglamorous and specific. It knows the largest piece its press can form and its trucks can carry, the radius its brake can hold, the joint a welder can actually reach wearing a hood, and the tolerance it can repeat on the four hundredth unit, not just the first.

A detail is only real once the company that has to make it says it can.

The clearest case is the curtain wall, where a single unit has to carry wind, keep water out, move with the building and still line up with the unit beside it. Four demands meet in one piece of aluminium and glass, and the shop knows which of the four will fight the others.

None of that sits in an architect's training and none of it belongs there. The architect owns what the wall has to look like and the engineer owns what it has to withstand, and between those two there is a band of decisions only the maker can settle.

Development teams tend to hear this as a scheduling preference. It is closer to a fact about where information lives, because a drawing describes a thing that does not exist yet, and the only people who know whether the description is achievable are the ones who own the machines.

A welder joining steel inside a fabrication shop, the work that turns a drawn detail into a finished building piece.

Why does the fabricator join before the drawings are finished?

Because once the drawings are finished the only moves left are expensive ones. Bringing the shop in while the detail is still soft means the fix is a changed line rather than a change order.

The sequence matters more than the calendar. The shop reviews the detail and says what it can hold and what it cannot, the engineer adjusts the criteria, and the architect decides whether the adjusted detail still does what the elevation needs. Three passes of that and the detail is both drawn and makeable.

Discover the same problem after release and the order of work inverts. The piece is already in production, so the building starts accommodating the piece, and the accommodation is usually a thickened slab edge, a shifted column line or a smaller opening nobody set out to draw.

What comes out the other end is not just a cleaner drawing. By the time a system is released, the model the shop helped settle is what prepares the shop drawings and drives the machines that cut and punch the steel. The drawing has become machine instructions, and nobody had to redraw it to get there.

That dependence also explains why so few shops can build an unusual assembly at all. The pool of companies with the equipment and the appetite is small, and it shrinks further as the assembly gets stranger.

Site conditions push in the same direction. 111 West 57th Street is the tallest and most slender residential building in the Western Hemisphere, and it was built in the courtyard of the landmarked Steinway Hall. A courtyard site puts a ceiling on how large a finished piece can be before it ever reaches the building, and that ceiling belongs in the detail long before it belongs in a logistics plan.

What a project gives up to get a makeable detail

A good engineer can push back on this, and the pushback is specific. Let a fabricator into the room early and it will quietly write the criteria around what it already makes, so the building ends up shaped by one company's standard product rather than by the design. I have seen that happen on packages where the criteria were loose.

I think the risk is real and manageable, and the control is simple. The performance criteria belong to the engineer, and as long as the engineer holds them, early involvement tells you what a detail costs in difficulty rather than what a shop would rather build.

The compromise underneath is narrower and harder to avoid. The shop that helps draw a detail is usually the shop that can build it, so the drawing starts to carry one company's way of working, and the field that could fairly price it later gets smaller as the detail gets better. I accept that trade on the assemblies with no precedent and refuse it on the ones that have plenty.

The same narrowing turns up again much later. A detail developed with one shop is documented in that shop's language, so the next company to touch it, years on for a repair or a replacement unit, has to learn a vocabulary never written down for anybody else.

Which details earn it is a judgment for the architect and the structural engineer, with a facade consultant where the facade is the hard part. On anything touching code compliance, structural adequacy or who carries design responsibility for a delegated system, retain the engineer of record and an independent facade consultant rather than reading a detail off a sample a shop brought to the meeting.

A building with few precedents is in the end a set of pieces somebody has to make, and the drawing that admits that early is the drawing that gets built.

Michael Stern is the founder and chief executive officer of JDS Development Group.

Photos by Zoshua Colah and Kyle Levesque on Unsplash

Sources

Engineering issues associated with delegated design
Findings Construction Federal Highway Administration

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