Shop drawings: what is actually in the set, and what to check
The set is an instruction, not a picture
Tender drawings describe a building. Shop drawings describe how that building gets made: which member, cut to what length, drilled with what holes, marked with what number, and lifted into which position. They are a different class of document, and they are the first drawings in the project that anyone has to be able to act on without asking a question.
The difference is not academic. A tender drawing can leave a connection marked "typical" and nobody is harmed, because nobody is cutting steel from it. A shop drawing that does the same thing stops a fabrication line, because a welder cannot cut a member from a typical detail.
So the set has one test, and it is worth applying sheet by sheet rather than as a general impression: can a fabricator cut from this, and can an erection crew place from this, without calling anyone? Every sheet that fails the test is unfinished, however tidy it looks. Neatness is not the criterion. Self-sufficiency is.
The general arrangement is not the deliverable
A general arrangement is the drawing everyone reads first, and it is usually the only one a client ever opens. It shows grids, elevations, spans, eave heights, the crane if there is one, and the outline of the building.
It also answers almost none of the questions that decide whether the building can be built. It does not say how the rafter connects to the column, what the bolt group is, how a purlin laps, where the bracing lands, or what number is painted on the member that goes at grid C between lines 4 and 5.
The failure that follows is common and expensive. A client approves a general arrangement, treats that approval as approval of the building, and then meets the connection details for the first time when the steel has already been cut and a question has become a variation.
Four sheets a set cannot work without
A complete set varies by building, but four components are not optional. If any one of them is missing or generic, the set cannot be issued.
The member schedule. One row per member: mark, section, length, quantity, and the grid position it belongs to. This is the sheet that ties the drawing to the packing list, and it is the sheet that makes an erection crew independent. If marks are assigned during packing instead of being taken from this schedule, the number on the steel describes a shipment rather than a position, and the site team has no way back to the drawing.
The connection details. Not "typical" everywhere. The joints that carry the building — column base, knee, apex, crane bracket, ridge, and any splice — need a detail a fabricator can drill and a checker can verify: plate thickness, bolt size and grade, hole diameter, bolt count, edge distances, and whether the connection is bolted on site or welded in the workshop. A single note covering eight different joints is one detail pretending to be eight.
The anchor bolt setting plan. This is the sheet that has to arrive before anyone pours concrete, and it is the one most often late, because it belongs to two parties at once. It gives the bolt template at every column position: bolt diameter, projection, gauge, embedded length, and the setting-out reference from the grid. Get it wrong and the error is not in the steel. It is in the foundation, which is the part nobody can re-cut.
The erection marking plan. Where each mark sits in the finished frame, the sequence it goes up in, and the temporary bracing with its removal condition. A mark register without a position is a parts list. A position without a sequence is a puzzle.
The interfaces are where a set runs thin
Every interface between the steel frame and something else is a place where two trades assume the other one has drawn it. That is where the thin sheets are, and it is predictable enough to check by name.
- Cladding and openings. Door and window positions, opening sizes, and the framing that carries them. A roller door 200 mm out of position is not a drawing error anyone notices until the door arrives.
- Crane rail and bracket. The bracket, the rail fixing, the rail level, and the clearance above the hook. Three suppliers, one datum, and it is usually nobody's sheet.
- Mezzanine and floor build-up. Who designs the mezzanine frame, and what the finished floor level does to headroom and to the stair.
- Foundation and plinth. Top of concrete, grout thickness, and the base plate that sits between them. This single dimension controls the finished floor level of the whole building.
- Services. Every penetration through a member or a roof sheet, and who is permitted to make it. An unlisted hole is a hole in a warranty.
The test is not whether an interface is drawn beautifully. It is whether it is drawn once, by one party, with the other party's dimensions already in it.
Revision control is what fails quietly
A set that is correct on the day it is issued and wrong two weeks later is worse than a set that was never correct, because people stop checking it.
Three habits keep a set trustworthy. Every sheet carries its own revision block and date. Marks are never reused for a different member, even when the original member was cancelled. Superseded sheets are withdrawn rather than merely re-issued, so the workshop copy and the site copy cannot diverge. None of this is difficult, and all of it is skipped when a project is running late — which is exactly when it matters.
What to check before you approve the set
You do not need to review a set sheet by sheet to know whether it is sound. Six checks will tell you most of it, and none of them needs anyone else in the room.
- Pick one mark at random and trace it: schedule, detail, erection position, packing list. Four documents, one number.
- Find the anchor bolt setting plan and confirm it exists before the foundation is poured, not after.
- Count how many joints are covered by the word "typical". More than a handful means the detailing was not finished.
- Check that the revision block is filled on every sheet. A blank is a signal, not a formality.
- Look for the temporary bracing and the condition for removing it. If it is not on the drawing, it will be decided on site by whoever is up there.
- Confirm the opening schedule matches the architectural drawings, dimension by dimension. This is the cheapest check you will make on the project.
What to ask before the first sheet is issued
- Will the member marks come from the erection drawing, so a mark on the steel leads back to a grid line?
- Which joints get a specific detail, and which are genuinely typical? Ask for the list.
- When does the anchor bolt setting plan arrive, relative to the foundation programme?
- Who owns the cladding, opening and crane-rail interfaces, and are their dimensions in your set?
- How are revisions issued, and how are superseded sheets withdrawn?
None of these questions is about steel sections. They are about whether the drawing set is a document a factory and a site can work from independently, or a description that still needs a phone call to become a building.
Written by Johnny Joe, who advises owners and project managers in Africa and South America on steel buildings. If a drawing set is what worries you on a live project, send the member schedule and one connection detail and I will tell you what the set is still missing.
Related: temporary bracing at erection · erection sequence as a design output · how to write a building brief · bay spacing trade-off
