Shop Drawings vs Concept Drawings in Metalwork Procurement

t491-33

Concept drawings show the design intent of a metal element, such as form, proportions and materials, while shop drawings give the fabricator the exact dimensions, connections, fixings and finishes needed to produce and install it. For procurement, concept drawings secure the design approval, but fabrication should only start once detailed shop drawings are agreed.

What a concept drawing shows

A concept drawing communicates the architectural idea. For metalwork, it typically shows the overall form of a gate, railing, pergola or window wall, its position in the building, the main proportions and the chosen material and general finish. It is drawn to support decisions by the client, the architect and the building committee.

Concept drawings are usually at a small scale and do not carry the detail a workshop needs. They are a strong starting point for pricing discussions and design approval, but they rarely contain enough information to cut, weld or install anything.

What a shop drawing contains

Shop drawings are the working documents for production. They are prepared at a larger scale and include exact dimensions, member sizes, weld and joint details, anchor and fixing positions, hardware locations, glass or infill specifications and finish requirements.

Dimensioned elevations and sections
Connection and fixing details
Material and profile schedules
Finish and coating specification
Installation notes and tolerances

Who prepares each document

The architect or designer usually prepares the concept drawings and coordinates the overall design. Shop drawings are often produced by the fabricator, or by a specialist detailer working with the fabricator, based on the concept and on site measurements.

In many projects the contractor or engineer reviews and signs off the shop drawings before fabrication. Clear responsibility at this stage prevents misunderstandings about who checks dimensions and structural adequacy.

Why the difference matters for procurement

Procurement decisions based only on concept drawings can lead to changes once the fabricator measures the site and develops details. A fixing that looked simple at concept stage may need a different base plate, or an opening may differ slightly from the drawing.

Treating the concept as the design basis and the shop drawing as the production basis helps keep schedules realistic and reduces rework on site.

How the approval sequence should work

A practical sequence starts with the concept drawing and written description, followed by on-site measurement. The fabricator then prepares shop drawings, which the architect or engineer reviews. Only after the client and design team approve these drawings should the factory begin production.

Concept drawing approved
Site measurement completed
Shop drawings prepared and reviewed
Written approval before fabrication

Checking shop drawings before approval

When reviewing shop drawings, focus on dimensions against measured site conditions, the location of fixings relative to the structure, the finish specified for the environment and any required guarding or handrail heights. For railings, the Israeli standard SI 1142 is a useful reference; exact required values should be confirmed with the engineer rather than taken from a summary.

Ask the fabricator to highlight any deviation from the concept, so changes are visible and agreed rather than discovered later.

Frequently asked questions

Can fabrication start from concept drawings alone?

It is not recommended. Concept drawings lack the dimensions and connection details a workshop needs, so production should wait for approved shop drawings.

Who pays for shop drawing preparation?

This should be agreed in the procurement documents before work begins, as responsibility varies between projects and contracts.

Do shop drawings need the architect's approval?

In most projects yes, or at least review by the design team and engineer, to confirm they match the design intent and building conditions.

Should shop drawings be prepared before site measurement?

Usually not. Accurate shop drawings depend on measuring the actual site, especially for existing openings and structures.

Common mistakes to avoid

A common mistake is approving a concept drawing and assuming it contains all production information. Skipping the written review of shop drawings is another, since dimensional errors are far cheaper to fix on paper than in finished metal.

Our recommendation

Agree early on who prepares, who reviews and who signs off shop drawings, and make written approval a condition before fabrication starts. Request that any change from the concept is marked clearly on the shop drawing.

Summary

Concept drawings define the design, while shop drawings define how it will be made and installed. Approving both in the correct order protects the schedule and the finished result.

השאירו פרטים ונחזור אליכם