Tendering and estimating, 29 October 2026
Reading construction drawings for pricing: a beginner's guide
To read construction drawings for pricing, start with the title block (drawing number, revision, scale and paper size), then the plans for lengths and areas, the elevations for heights and openings, the sections for build-ups, and the notes and spec for materials. Use written dimensions; scale off only when there's no figure and you've checked the scale.
What's in a set of construction drawings?
A typical domestic or small commercial set has the same few drawing types, each answering different pricing questions. Read them in this order and you'll know where to look for each number.
| Drawing | Usual scale | What it tells you for pricing |
|---|---|---|
| Location plan | 1:1250 | Where the site is; access and neighbours |
| Block or site plan | 1:500 | Building footprint, drains, boundaries, access for deliveries and skips |
| Floor plans | 1:50 or 1:100 | Wall lengths, room sizes, door and window positions, electrical and plumbing layouts |
| Elevations | 1:50 or 1:100 | Wall heights, window and door sizes, roof pitch, external finishes |
| Sections | Often larger than the plans | Wall, floor and roof build-ups: insulation, blocks, joists, ceiling heights |
| Details | Larger again | How junctions are built: eaves, thresholds, cavity trays |
Typical scales vary by council. One council's planning guidance asks for location plans at 1:1250, block plans usually at 1:500, and floor plans and elevations usually at 1:50 or 1:100. Building regulations and construction drawings add the sections and details.
How do you read the title block?
The title block is the box in the corner of each sheet. Read it before anything else, because it tells you whether the drawing is current and how to measure it.
Look for the drawing number and revision (rev A, rev B), the scale and paper size ("1:50 @ A1"), the status (for planning, for tender, for construction) and the date. A drawing marked "for planning" is often less detailed than you need to price. Note every drawing number and revision you priced from, and put that list in your quote.
How do you use the scale?
A scale tells you how many real millimetres one millimetre on the paper represents. At 1:50, 1 mm on paper is 50 mm on site. The scale only holds at the paper size stated in the title block.
Scaling off a drawing, and the A3 trap
A wall on a floor plan marked 1:50 @ A1 measures 80 mm with your rule. The same A1 sheet printed on A3 paper. A3 is 297 × 420 mm and A1 is 594 × 841 mm, so everything prints at half size.
| Real length at 1:5080 mm × 50 | 4,000 mm (4.0 m) |
| Same wall at 1:10080 mm × 100 | 8,000 mm (8.0 m) |
| Measured on the A3 print80 mm ÷ 2 | 40 mm |
| Wrongly read as 1:5040 mm × 50 | 2.0 m |
| Correct reading on A340 mm × 100 | 4.0 m |
Always check the scale against a written dimension first. If a door marked 900 mm wide doesn't measure 18 mm at 1:50, the print isn't at the stated scale. Many drawings carry a "do not scale" note: that means use the written figures, and ask for any missing dimension rather than measuring it.
What should you pull out of each drawing for pricing?
Work through the set with a list, so nothing priced comes from memory. This checklist covers the items most often missed on small jobs.
The last two lines matter most. A drawing set that doesn't show foundations or drainage isn't telling you they're free: it's telling you someone hasn't designed them yet. Price them as provisional or exclude them, in writing. The guide to pricing when drawings are indicative covers how.
What do the lines and symbols mean?
Thick lines are usually walls cut through on plan; thinner lines are things seen beyond, like worktops or the line of a roof above. Dashed lines usually show something hidden or above: a beam, a roof overhang, a foundation. Hatching shows materials in section: brick, block, insulation and concrete each have their own pattern.
Every set should have a legend or key. Electrical and plumbing layouts depend on it: match every symbol on the layout to the legend before you count. If there's no legend, ask for one rather than guessing what a symbol is.
What if you've never been taught to read drawings?
Most small-firm owners learned on site, not from drawings, and it shows when they start tendering. Start on a job you've already built: lay the drawings next to what you know was built and match them up. That's the fastest way to learn what each line means.
I don't know how to read drawings.
He's 23, runs six people including his dad, and had been pricing commercial roofing at about £60 a square metre when the work was going for nearer £36.50. Learning the drawings, and getting his overheads per man-day right, came together: one tells you the quantity, the other tells you the rate.
Once you can read the set, doing a quantity take-off is the next step. If you're short of time, an AI take-off tool can do a first pass as long as you check it.
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 drawings, you forward the PDFs to Nexley on WhatsApp or email. It reads the title blocks and scales, measures the quantities, lists what isn't shown as queries and assumptions, and prices the job against your rates. You check it and approve the price, and you can ask it in plain English what any part of a drawing means.
Common questions
What does "do not scale" mean on a drawing?
It means you should use the written dimensions, not measure the drawing with a rule. Prints and PDFs can be resized, so scaled measurements may be wrong. If a dimension you need isn't written, ask the designer for it and note it as a query.
What scale are house drawings usually at?
Floor plans and elevations are usually at 1:50 or 1:100, block plans at 1:500 and location plans at 1:1250. Sections and details are often drawn at a larger scale to show the build-up. The title block states the scale and the paper size it applies to.
Which drawing shows the roof pitch?
Usually the elevations or a section through the roof. The pitch is often written in degrees. If it isn't, ask: measuring a pitch off a small-scale drawing is easy to get wrong, and it changes the roof area.
What if the drawings and the spec disagree?
Raise it as a query before you price, and say in your quote which you priced. Many contracts set an order of priority between documents, so read the tender instructions. Don't pick the cheaper option silently.
Sources
- Torbay Council: Drawing plans to scale
- Papersizes.org: A series paper sizes
- Designing Buildings: NRM2, detailed measurement for building works
Every rule, rate and date above was checked against these sources on the date shown at the top.
Topic: Tendering and estimating
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