Steel detailing is often quoted per tonne, but the per-tonne figure is a way of expressing the price, not what sets it. Detailing cost follows the number of pieces, connections and drawings in the job, the quality of the design drawings and how many revisions come through. Two frames with the same tonnage can need very different detailing effort. This guide explains the pricing models detailers use, what drives the hours behind them, and how to compare detailing quotes fairly. For a fixed price on your project, send us the drawings.
What steel detailing produces
Detailing turns the engineer's structural drawings into the information a shop and an erection crew need to build the frame. On most structural steel jobs the detailer builds a 3D model, then produces:
- Erection drawings (sometimes called E-sheets or erection diagrams): plans and elevations showing where every piece goes, with piece marks, so the crew can set the frame.
- Shop drawings or assembly drawings: one drawing per assembly, such as a beam with its connection plates, showing cuts, holes, copes, welds and dimensions.
- Single-part drawings: plates, angles and fittings drawn individually for cutting and drilling.
- Anchor bolt or setting plans: layout of anchor rods and embedded items that the concrete trade places before the steel arrives.
- Bills of materials and NC files: lists of every piece by size, length and grade, and machine files that feed cutting and drilling equipment.
The point for cost is that every one of those outputs scales with the number of pieces and assemblies, not with weight.
The four ways detailing is priced
Per tonne
The detailer, or the fabricator's estimator, works out the tonnage from the drawings and quotes a rate for each tonne. It's popular because tonnage is known early and it lines up with how the fabrication and erection are priced. The weakness is that it hides the real driver. A detailer who quotes per tonne has already estimated the hours and divided by weight, so the rate changes from job to job.
Per drawing or per sheet
Some detailers price by the number of drawings they expect to produce. This tracks effort more closely than weight does, but the sheet count is itself an estimate until the model is built, so check how extra sheets are handled.
Per hour
Hourly rates are common for small jobs, for revisions and change orders after the base scope is detailed, and for consulting work such as checking someone else's drawings. Ask for an estimate of hours and a cap, or you're carrying the risk of the job growing.
Lump sum
A fixed price for a defined scope, usually based on a specific drawing set and revision. This is the easiest to budget, provided the scope is written down: which drawings, which revision, what is excluded, how many revision cycles are included and what happens after that.
None of these models is cheaper by nature. They are different ways of sharing the risk that the job takes more hours than expected.
What drives detailing hours
Pieces and assemblies per tonne
This is the biggest single factor. A tonne of heavy columns might be a handful of assemblies. A tonne of lintels, posts, bracing, girts and plates can be dozens. Each assembly needs a drawing, each part needs a mark, and each connection has to be modelled and checked. Light, piece-heavy jobs always cost more per tonne to detail.
Connections
Simple, repeated shear connections model quickly, especially when the engineer has specified standard connection types. Moment connections, skewed or sloped members, members framing in at odd angles, and connections that change from bay to bay all take longer. On many Canadian projects the fabricator is also responsible for designing connections, which adds engineering time and calculation packages to the scope. Ask every bidder whether connection design is in or out.
Repetition
A warehouse with identical bays repeats the same assemblies many times, and a good model lets the detailer reuse them. A renovation or custom house with a different condition at every beam doesn't.
Completeness of the design drawings
Missing dimensions, unclear elevations and conflicts between the architectural and structural sets turn into requests for information (RFIs). Every RFI costs detailing time to write, track and incorporate. A drawing set issued for construction, with dimensions, member sizes and connection forces shown, details faster than one issued for tender.
Revisions
Design changes after detailing starts are one of the main reasons detailing invoices exceed quotes. A change to a grid line or a floor elevation can ripple through dozens of drawings. Most detailing quotes include a set number of review cycles and price further revisions separately, so read that clause.
Miscellaneous metals
Stairs, railings, ladders, lintels, embed plates and small supports are drawing-heavy for their weight. A stair can need as many sheets as a long run of beams. If misc metals are in your package, expect them to raise the detailing cost per tonne of the package as a whole. Our miscellaneous metal fabrication guide covers what usually falls in that category.
Finish and exposure
Architecturally exposed steel needs more careful detailing of weld finishes, bolt patterns and member alignment, because the result will be seen.
Schedule and sequencing
Fast-tracked jobs are often detailed and released in sequences so the shop can start before the whole building is drawn. That adds coordination and more submittal cycles.
Model and coordination requirements
Some projects require the detailer's model to be shared for coordination with other trades, or delivered in a particular format. That is extra scope, and it should be listed.
Detailing as part of the fabricated steel price
On most structural steel jobs the owner or contractor never sees a separate detailing price. The fabricator includes shop drawings in the supply or supply-and-install quote, along with material, shop labour, finish, delivery and sometimes erection. Our guide to structural steel price per tonne explains how those parts stack up.
That bundling matters when you compare quotes:
- A fabricator quote that excludes shop drawings isn't comparable to one that includes them.
- If you hire a separate detailer, the fabricator still has to review the drawings against how their shop works. Ask whether they charge for that.
- When the fabricator details in-house, the shop and the detailer are the same company, so a fit problem has one owner.
If you're buying detailing on its own, our related post on steel shop drawings cost looks at it from the owner's side, and steel detailing services in Canada covers how to choose a detailer.
How to compare steel detailing quotes
Put the quotes side by side and check that they cover the same work:
| Item | What to confirm |
|---|---|
| Drawing set | Which drawings and which revision the quote is based on |
| Tonnage | What tonnage each bidder carried, and whether it includes connection material |
| Deliverables | Model, erection drawings, assembly drawings, single parts, anchor bolt plans, NC files |
| Connection design | Included or excluded, and who stamps the calculations |
| Misc metals | Stairs, rails, lintels and embeds in or out |
| Review cycles | How many submittals and revision rounds are included |
| Extra work | Hourly rate or unit rate for revisions and change orders |
| Schedule | When the first submittal will be ready, and whether it is released in sequences |
A low per-tonne rate that leaves out connection design, misc metals or revisions often ends up costing more than a higher rate that includes them. Whether shop drawings must be sealed by an engineer depends on the project and the specification; see do shop drawings need an engineer's stamp in Ontario.
How to keep detailing costs down
- Send a complete, current drawing set. Structural and architectural drawings, the specification, and any connection details the engineer has prepared.
- Settle the design before detailing starts. Every change after the model is built costs time.
- Answer RFIs quickly. Detailing stalls while questions wait, and stalled jobs cost more to restart.
- Use standard connections where the engineer allows it. Repeated, simple connections detail and fabricate faster.
- Keep the scope in one place. If the same fabricator details, fabricates and delivers, you avoid paying for hand-offs and duplicate checking.
Get detailing priced with your steel
We prepare a detailed take-off and quote from your structural or architectural drawings free of charge. Once the job is approved, we produce the shop drawings in-house, and engineering services are available for projects that need them. Fabrication follows in our CWB-certified shop, with delivery and installation across the GTA and Ontario.
Send your drawings for a free quote, or see our services for shop drawings, fabrication, delivery and installation.
Frequently asked questions
How is structural steel detailing usually priced?
Detailers quote per tonne of steel, per drawing sheet, per hour, or as a lump sum for a defined scope. A per-tonne rate is common on building frames because tonnage is known early from the take-off, but the rate behind it still comes from the hours the job will take.
Why does steel detailing cost more per tonne on small jobs?
Detailing effort follows pieces, connections and drawings, not weight. A small job with many light members, plates and connections can need as many drawings as a much heavier frame of large beams, so the cost spread over each tonne is higher.
What is included in a steel detailing quote?
Usually the 3D model, erection drawings, shop or assembly drawings, single-part drawings, bills of materials and CNC files for the shop. Check whether connection design, RFIs, revisions and miscellaneous metals are included, because those vary the most between quotes.
Is it cheaper to hire a separate detailer or let the fabricator detail?
It depends on the job. A separate detailer can be the right choice for some owners, but when the fabricator details in-house there is one point of responsibility for drawings and fit, and no hand-off between two companies when something changes.
