What Are Shop Drawings?
A shop drawing is a detailed, dimensioned drawing a fabricator or manufacturer prepares to show exactly how a component will be built, fabricated, cut, and installed. Where the design drawings (the "IFC" or issued-for-construction set) show a steel stair in the architect's intent, the shop drawing shows every bolt, weld, notch, gusset plate, stiffener, and finish callout for that specific stair.
Think of it this way: the design drawing says what to build; the shop drawing says exactly how it will be made, to the millimetre, on the fabricator's own equipment and with the fabricator's own material.
“Design drawings define the project. Shop drawings define the parts — and that distinction is where most schedule surprises hide.”
Who Prepares Shop Drawings — and Who Checks Them?
Shop drawings are prepared by the trade contractor or fabricator who will actually manufacture or install the work — not by the design engineer. The steel fabricator produces the steel shop drawings. The curtain wall supplier produces the glazing and framing shop drawings. The millworker produces the joinery drawings.
That sounds clear enough, but here's the part that trips up general contractors and subconsultants: the design engineer of record reviews and stamps approval on those shop drawings before fabrication can proceed. In Ontario, structural shop drawings for steel and misc metals nearly always require a P.Eng. review, and the engineer of record or their delegate has to verify that the shop drawings conform to the intent of the engineered design — the connection details, member sizes, and loads.
What Actually Causes Fabrication Delays
Base on hundreds of Ontario projects, these are the five most common shop-drawing delay traps we see:
Shop drawings not started until the last minute
Fabricators often sit idle waiting for a green light. If the review-and-approve sequence isn't scheduled like a manufacturing lead time, the steel is late no matter how fast the install team works.
Incomplete or unclear design drawings
If the architect's package doesn't have every dimension and elevation resolved, the fabricator has to make assumptions — and then the engineer rejects those assumptions. Rejection is rework, and rework is schedule.
Shop drawings sent to the wrong reviewer
Structural connections go to an architect who isn't a P.Eng. and sits on them. Meanwhile the steel is waiting. The review routing needs to be specified, not assumed.
One round of review treated as final
Professionals know the same detail will likely go back twice. If the schedule only budgets one round, the second resubmission blows the milestone.
Coordination between disciplines
The glazing shop drawing references anchor points that the steel shop drawings haven't confirmed, and vice versa. When trades don't coordinate their drawings, the field discovers the conflict at install — the most expensive moment to find it.
How a Dedicated Shop-Drawings Team Keeps Your Schedule
This is exactly where May Engineering Inc's shop-drawings service earns its keep. We prepare and/or review shop drawings for curtain wall, glazing, cladding, miscellaneous metals, and millwork — and we coordinate the review sequence so the fabricator, the architect, and the engineer of record are all reading the same drawing at the same time.
When an Ontario project of ours needs structural steel, we don't let the fabricator's shop drawings drift through three uncontrolled review cycles. We tighten the turnaround, we check the connections against the design, and we get the P.Eng. approval stamped and out the door on a schedule the site can actually build to.
Why It Matters More Than the Drawing Itself
A shop drawing isn't paperwork — it's the handoff between design intent and physical reality. Get it right, and the curtain wall you designed fits the opening the steel team built, first try. Get it wrong, and you're cutting anchors in the field, ordering replacement glazing units on a 12-week lead time, and explaining the overrun to a client who saw it coming.
Thinking about a project with fabricated components — steel framing, glazing, cladding, or millwork? Our shop drawing & fabrication drawing services handle the review before you award the fabrication contract — it's dramatically cheaper to schedule the review in than to rescue it after. Request a quote to get started.
Keeping your fabricated components on schedule?
May Engineering Inc prepares and reviews shop drawings for steel, glazing, cladding, and millwork across Ontario — coordinated to keep fabrication moving.
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