How to do a structural steel take-off (and how AI does it now)

What a take-off is for

The material take-off (MTO) is the list of everything you need to buy and fabricate. It drives three things: what you order from your steel supplier, how many hours you allow in the shop, and the price you put on the quote. Every error flows straight through to your margin.

Step by step

1. Check the drawing register and revisions

Before counting anything, confirm you have every sheet and the latest revision of each. Note the revision letters on your take-off so you can tell later what changed.

2. Work sheet by sheet

Go through the general arrangement plans, elevations, sections and connection details in order. Mark each member off on the drawing as you list it, so nothing is counted twice and nothing is missed.

3. List the main members

For each beam, column and rafter, record the section, grade, length and quantity. Australian section names carry their mass per metre, so a 310UB40.4 weighs 40.4 kg per metre. That makes weights quick to calculate and easy to check.

4. Add the secondary steel and connections

Bracing, cleats, base plates, stiffeners, splice plates, purlins and girts (where they're in your scope), plus bolts and anchors. Connection material is where most under-quoting hides.

5. Calculate weights

For sections, multiply mass per metre by length. For plate, multiply length by width by thickness by the density of steel (about 7,850 kg per cubic metre). Total weight drives both material cost and handling.

6. Work out the coating area and weight

Painting and powder coating are usually priced by surface area, while galvanising is commonly priced by weight, so work out both. Section tables give the surface area per metre for each section; add the plate areas, including edges, on top. See how to price finishing.

7. Allow for stock lengths and cut loss

Steel comes in stock lengths. Check what your supplier carries and plan the cuts, because the offcuts are a real cost to the job.

8. Turn the gaps into RFIs

Missing sizes, unclear connections, a construction category that isn't stated: write each one down as a question for the builder or engineer, and state your assumption on the quote.

9. Get a second check

A second set of eyes on the totals and the big-ticket items catches most expensive errors before they're priced.

The mistakes that cost the most

• Counting the same member twice, because it appears on a plan and again on a section or elevation.
• Working from a superseded revision.
• Missing connection material, such as cleats, plates and bolts that only appear in the details.
• The wrong grade or a missed note about it.
• Not stating exclusions, so the builder assumes they're included.

How AI take-off works

AI take-off tools read the PDF drawing set the way an estimator would: page by page, picking out member marks, sizes, lengths and quantities, and building the material list. A good tool should:

• show which drawing each line came from, so it can be checked against the page;
• give each line a confidence level and flag the ones it isn't sure about;
• avoid double counting members that appear on more than one view;
• turn missing information into a list of RFIs; and
• let the estimator approve the list before it goes anywhere near a price.

The point isn't to replace the estimator. It's to move them from counting to checking, which is faster and where their experience matters most.

AI take-off in Factory Hub

Factory Hub reads your drawings page by page, gives every line a confidence score with a "check these" list, turns missing details into RFIs, and feeds the approved take-off straight into the quote, with finishing calculated from weight or surface area. Every Factory Hub subscription includes 3 AI take-offs a month, with estimating plans for shops that quote every week.

Weights and areas in this guide are general rules of thumb. Always confirm section properties against your supplier's current tables.

Common questions