What Happens When Shop Drawings Are Off

Shop drawings are supposed to be the plan everyone follows — but when they’re wrong or incomplete, the entire job starts to unravel. Material gets ordered to the wrong size, frames don’t line up with openings, and glaziers end up improvising in the field. That’s how delays, rework, and change orders start piling up.

Here are just a few examples of what can go wrong:

Wrong frame sizes → Now your glass doesn’t fit.

Joint dimensions off → Joints too big, or worse not big enough.

Example:
The shop elevation must match the given dimensions to avoid incorrect glass sizing or a frame that doesn’t fit. It’s the drafter’s responsibility to add details the architect may have overlooked, such as joint sizes or differences in system width between the architectural drawings and the quoted system.

In this case, the architect specified 2¼-inch jambs and sill, while the quoted system uses a 2-inch face all around.

Missing fastener details → Crews lose time trying to figure it out on site.

Example:
In this shop drawing, the strap anchor is required — but nowhere does it show where it goes or what it fastens into. That means crews are left to figure it out in the field, costing time and opening the door to mistakes. Even standard conditions need standard documentation.

Miscalculated quantities → You’re short on materials or over budget.

None of this is about being careless — it’s usually because something slipped through the cracks. And when it does, it costs everyone: your team, the fabricator, the GC, and your reputation.
The good news? Most of these issues can be caught before they reach the field — if you know what to look for.

Catching Problems Before the Field Does

One of the biggest advantages of accurate shop drawings is their ability to catch design issues before they become jobsite problems. That’s not just a bonus — it’s the whole point.

Take this common scenario:
You’re handed a set of architectural drawings. Everything looks fine at a glance. But once you start drafting, you notice the floor plan shows one thing and the elevation shows something different. Or the door callout says 36″, but when you account for joints and frame profiles, there’s not enough space for it to actually fit.

That’s where detailed shop drawings earn their keep. They force a closer look. They surface the inconsistencies that would otherwise go unnoticed until it’s too late.

In practice, that might look like:

• Spotting a mismatch in opening dimensions
• Realizing a joint was never accounted for
• Flagging a detail that doesn’t match the building conditions
• Catching structural gaps that would affect anchoring

When you catch these issues early, you give your team time to fix them the right way — through an RFI, a revised layout, or a simple confirmation from the architect. That’s a lot better than scrambling in the field with a delivery truck full of frames that won’t fit.

The Small Details That Make a Big Difference

A good shop drawing doesn’t just show what to build — it shows how to make the install go smoothly. That’s where the details matter most. The kind of details that save you hours (or days) on-site.

One of the best examples?

Fastener locations.

If a drawing shows the wrong anchor spot — or skips it altogether — your crew might not realize until they’re drilling too close to a concrete edge. Now you’ve got a structural problem and possibly a delay while someone figures out a workaround.

Other critical details that impact install:

• Edge distances that meet structural requirements

Example Scenario:
In the drawing example, notice how the fastener location is called out in relation to the concrete edge. That detail might look small, but it’s critical. If the anchor is placed too close to the edge, the concrete can crack or fail under load, forcing the crew to stop and find a workaround. That’s why the drawing includes a note for the engineer to confirm minimum edge distance. A good shop drawing doesn’t just show where the system sits—it anticipates these structural realities so installers aren’t left guessing on-site.

• Surrounding conditions that affect how frames go in
• Correct fastener types for the substrate (steel vs. CMU, etc.)
• Clear locations and offsets so installers don’t have to guess

Every one of these can be the difference between a smooth install and a time-wasting back-and-forth. And they’re not just for the field — fabricators rely on this info too, especially when it comes to prep work and hardware.

If those details are missing or wrong, you’re going to hear about it — and probably not in a polite way.

What We Do When the Plans Are Unclear

Architectural drawings aren’t always perfect. Field conditions change. Specs get missed. Sometimes you’re working with half the information you need — but that doesn’t mean the shop drawings can afford to be wrong.

At MP Drafting, we make it a point to flag issues before they become jobsite problems. When something doesn’t add up, we don’t guess — we call it out. If an opening dimension doesn’t match between sheets, or fastener placement doesn’t meet structural edge distances, we’ll put a note on the drawing or prompt your team to send in an RFI.

It’s not about slowing the process down — it’s about helping you avoid surprises later.

What we do when drawings are unclear:

• Add clarification notes where details are missing or conflicting
• Highlight potential structural concerns tied to anchoring or joint sizes
• Identify areas where an RFI may be needed — and call them out clearly
• Keep open communication with your team throughout the submittal process
  (If you want to learn more about MP Drafting’s internal “Standard Operating Procedure”, check out this article, LINK)

Here’s a real example: The architect drawings didn’t show the finished floor build-up, the fastener location wasn’t confirmed, and door swings conflicted across sheets. Instead of guessing, we flagged these items directly on the shop drawing. That way, the contractor could get answers before the jobsite was impacted.

It’s not just about delivering a drawing — it’s about helping you submit something that holds up under pressure.

Example scenario of what happens when info is missing:

Example scenario of what happens when sheets contradict each other:

Great Shop Drawings Take Teamwork

One thing we run into often: the assumption that a drafting team can just take a set of plans, fill in the blanks, and crank out a perfect set of shop drawings.

But here’s the truth — the best results come from collaboration.

Every glazing contractor works a little differently, and unless preferences are shared early — anchor types, joint sizes, field vs. shop assembly, and more — the drafting team is forced to make assumptions.

And assumptions lead to revisions, delays, and frustration.

Here’s what makes the difference:

• Clear direction on your preferred details
• Timely answers to questions or clarifications
• Reviewing drafts with your field or fabrication teams in mind

Why does this matter? Because the cost in time to revise a full set of shops is always more than the time it takes to answer a few questions or mark up a drawing in advance. On large projects, that collaboration can save thousands of dollars.

A real-world example: Many architects will mark up a third line of sealant on their drawings. If a drafter simply includes it without clarification, the PM may be on the hook to provide and install an expensive, unnecessary scope item. By flagging and resolving that detail during the shop drawing review, you avoid wasted cost, rework, and disputes before the job ever reaches the field.

We’re not just here to draw. We’re here to help you turn a bid into a build — and that means staying aligned from day one. When shop drawings are treated as part of your project planning strategy, not just a box to check, you end up with a smoother install, happier partners, and fewer late-game problems.

Wrap-Up: Be the One Who Catches It Before the Jobsite Does

Accurate shop drawings don’t just make your submittals look good — they help your whole job run smoother. They reduce questions. Prevent change orders. Save your field crew from having to “figure it out” under pressure.

At MP Drafting, we’ve seen firsthand how much easier a project goes when the details are right the first time — and we built a simple tool to help you get there.

Download the Free Tool: Shop Drawing Accuracy Checklist

10 Things to Confirm Before You Fabricate or Install (PDF)

Make sure your next set of drawings checks all the right boxes — and avoids the costly surprises.