Can AI do a take-off from architect's drawings? How to test it on roofing, brickwork and electrical

Yes, for a first pass. AI tools can read clear PDF drawings, find walls, rooms and roof areas, and produce quantities in minutes. They still miss things: wrong scales, openings, hidden details and notes in the spec. Treat an AI take-off like a junior's: test it on a job you've already priced, then check every big quantity before you price from it.

What can AI read on an architect's drawing?

Dedicated take-off tools are built to read drawings: they detect rooms, walls and objects on a PDF or image and measure them. A general AI chat tool may only read the text in a PDF, so check before you rely on it.

Two kinds of tool get called "AI take-off":

• Dedicated take-off software. Products such as Togal.AI describe themselves as detecting, labelling and measuring spaces, walls and objects on plans, from PDF and image files. These are built for drawings.
• General AI assistants. ChatGPT, Claude, Gemini and Copilot can look at images, but their handling of drawings varies. OpenAI's help page on file uploads, as of October 2026, says that for PDFs with text and images in some modes ChatGPT will only analyse the text, and that image-only PDFs aren't supported. Many drawings are exactly that: a scanned or flattened image.

The practical rule: if a tool can't show you where it measured, you can't check it.

How do you test an AI take-off before you trust it?

Run it on a job you've already priced and built, where you know the real quantities. Twenty minutes on an old job tells you more than any sales demo.

1. Pick a finished job.

   One with clear drawings and a take-off you trust, ideally one you checked against the delivery notes.

2. Give the tool only what a tenderer would get.

   The drawings and spec as PDFs. No hints.

3. Ask for quantities with workings.

   "List each item, the drawing it came from, the dimensions used and the quantity." A number with no working is useless.

4. Compare line by line.

   Note every item that is more than 5% out, and every item it missed entirely.

5. Check how it handled scale.

   Ask what scale it used. If it measured off a drawing that says "do not scale", that's a fail on that item.

6. Repeat on a different trade.

   A tool that's good on floor areas may be poor on roof pitches or point counts.

Worked answers to check against

Use these three small take-offs as a calibration test: give the tool the same dimensions and see if it gets the same answers. Each uses published coverage figures, so you can see where an AI goes wrong.

Worked example

Roofing: one 40 m² slope in interlocking concrete tiles

A single slope measured on the slope (not on plan) at 40 m², tiled in Marley Modern at 75 mm headlap.

Tiles40 m² × 9.9 per m²	396
Tiles with 5% waste396 × 1.05	416
Pallets of 192416 ÷ 192 = 2.17	3 pallets
Battens40 m² × 2.9 linear m per m²	116 m

The plan-versus-slope check: plan area = slope area × cos(pitch). At 35°, cos is 0.819, so 40 m² of slope shows as 32.8 m² on a roof plan. If the AI quotes roughly 33 m², it measured the plan.

Worked example

Brickwork and electrical: two quick checks

Brickwork: three walls totalling 10 m long, 2.4 m high, with a 3.0 × 2.1 m door and a 1.2 × 1.2 m window. Electrical: a ground-floor layout showing 8 double sockets, 2 fused spurs and 6 downlights.

Gross area10 m × 2.4 m	24.00 m²
Openings6.30 m² + 1.44 m²	−7.74 m²
Net area per skin	16.26 m²
Facing bricks16.26 × 60 per m²	976
Points to price8 + 2 + 6	16

Where do AI take-offs usually go wrong?

In the same places a rushed human does, plus a few of their own:

Coverage is where small errors become big ones. A roofing and cladding firm in Ireland we spoke to found an AI-assisted check corrected a board coverage figure from 0.75 to 1.44 m² per board, and flagged an adhesive that wasn't compliant for use on XPS board. Get coverage wrong by that much and you order nearly twice the boards you need.

How accurate can an AI take-off be?

Accurate enough to price from, once checked. A renovation and extension builder with four or five staff told us the roof timber take-off came out "pretty much bang on" against his QS's figures. That's one firm and one comparison, not a promise.

The useful way to think about it: AI is fast at the measuring and arithmetic, so your time moves from measuring to checking. On a tender where you'd spend a day measuring, an hour of checking is a good trade. On a drawing set that's indicative or incomplete, no tool can measure what isn't drawn: see pricing a tender without a site visit.

Should you use AI or a QS for take-offs?

Use a QS for large, complex or high-risk packages, or where the client expects a formal bill. Use AI, checked by you, for the many smaller tenders you'd otherwise not have time to price. Plenty of firms do both.

If you're comparing tools, the guides to the best take-off software for small UK firms and construction estimating software cover the options. For the checks before you price from any AI output, see what to check before using AI for tender pricing. And if reading the drawings yourself is the hard part, start with reading construction drawings for pricing and how to do a take-off.

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Where Nexley fits

Nexley is the AI back office for UK trade firms: five AI assistants run your tenders, quotes, buying, scheduling and invoicing. It connects to the tools you already work in, you run it all from WhatsApp, and you approve everything. £799 a month.

For take-offs, you forward the drawings and tender pack to Nexley on WhatsApp or email. It measures the quantities, shows the drawing and dimensions behind each one, uses manufacturers' coverage figures, and lists its assumptions and queries. You check the take-off and approve the price before it goes anywhere.

Start 7 days freeSee take-offs and bills of quantities

Common questions

Sources

1. OpenAI Help: Uploading files to ChatGPT
2. Capterra UK: Togal.AI
3. Roofing Superstore: Marley Modern interlocking concrete roof tile
4. Beesley & Fildes: How many bricks per m²
5. Papersizes.org: A series paper sizes
6. Bluebeam UK: Pricing

Every rule, rate and date above was checked against these sources on the date shown at the top.