Estimating and bidding

How to read construction plans for estimating

Read plans for estimating in a set order: check the sheet index and addenda, read the general notes and specifications, understand the floor plans at the right scale, then use sections, details, and schedules to find what the floor plans do not show. Mark up scope as you go, and write questions before you count anything.

Strapped lumber, concrete blocks and a parked telehandler in a commercial construction staging area.
Material quantities, delivery timing and equipment availability shape the next phase of work. AI-generated illustration.

Reading plans for estimating is different from reading them to build. A foreman looks for how to install something. An estimator looks for everything that costs money and everything that is missing. Start with the sheet index and addenda so you know you have the full set. Read the general notes and the specifications for your scope. Then work through the floor plans, using elevations, sections, details, and schedules to fill in what the plan view hides. Mark every item of your scope as you find it, and list questions as you go. Counting comes last, in the quantity takeoff.

How a drawing set is organized

Most commercial sets are grouped by discipline, each with a letter prefix. The exact letters vary by architect, but a typical set looks like this:

Common sheet prefixes in a drawing set
PrefixDisciplineWhat estimators look for
G or TGeneral / title sheetsSheet index, code data, abbreviations, symbols legend
CCivilGrading, utilities, paving, site work quantities
LLandscapePlanting, irrigation, hardscape
SStructuralFoundations, framing, steel, general structural notes
AArchitecturalFloor plans, elevations, sections, details, finish and door schedules
M, P, FPMechanical, plumbing, fire protectionEquipment schedules, piping and duct layouts, risers
EElectricalPower, lighting, panel schedules, one-line diagram

The project manual holds the specifications, usually organized by MasterFormat divisions (see MasterFormat). Drawings show where and how much. Specs show what quality and which products. You need both.

Step by step: reading plans for an estimate

1. Confirm you have the complete, current set

Check every sheet against the index. Note the issue date and revision on each title block. Collect every addendum, because addenda often reissue sheets or change specs. An estimate built on a superseded sheet is wrong before it starts.

2. Read the general notes and the legend

General notes on the first sheets of each discipline often carry scope that appears nowhere else: "contractor shall patch and paint all walls disturbed by work," "provide blocking for all wall-mounted items." The symbols legend and abbreviation list tell you how this architect draws things. Do not assume one firm's symbols match the last set you read.

3. Read your spec sections before your drawings

Read the specification sections for your trade, plus Division 01. Look for products, approved manufacturers, testing, mock-ups, warranties, and submittal requirements. A spec calling for a specific manufacturer with no substitutions can change your price a lot.

4. Learn the floor plans and check the scale

Find the scale on each drawing, not just the sheet. A floor plan at 1/8 inch = 1 foot and an enlarged plan at 1/4 inch = 1 foot can share a sheet. Check the scale against a printed dimension before measuring anything, especially on PDFs, which may not print at true size. Locate grid lines, room names and numbers, and north arrow. Note where your work starts and stops.

5. Follow the references to sections, details, and elevations

Callout bubbles on plans point to details elsewhere. A detail reference like 5/A501 means detail 5 on sheet A501. Section cuts show heights, layers, and assemblies that the plan view flattens. Wall types, ceiling heights, and soffits often live only in sections and reflected ceiling plans. This is where hidden scope usually sits.

6. Use the schedules

Door, window, finish, fixture, equipment, and panel schedules are ready-made quantity lists with sizes and types. Cross-check them with the plans. If the door schedule lists 42 doors and you count 44 on the plans, that is an RFI.

7. Check the other disciplines for your scope

Work for your trade often shows up on another trade's sheets. Electrical connections to mechanical equipment appear on M sheets. Structural steel embeds in concrete show on S sheets. Concrete housekeeping pads might be on M or E sheets. Skim every discipline for anything that touches you.

8. Mark up scope and write questions

Color-code scope on the drawings as you go: one color for included, one for excluded, one for questions. Keep a running list of conflicts and gaps. Send real questions to the architect or GC as a pre-bid RFI by the question deadline, and turn unresolved items into clear bid qualifications.

Worked example: a flooring contractor on a clinic fit-out

Say a flooring contractor reviews a 14,000 square foot clinic set. On the A1 floor plan, rooms are tagged with finish codes. The finish schedule on A6 shows three floor types: LVT in corridors, sheet vinyl with integral cove base in exam rooms, and carpet tile in offices. The spec section for resilient flooring requires a moisture test on the slab before installation, and the general notes say the flooring contractor provides floor prep. An enlarged plan on A2 at a larger scale shows the exam room layout, and a detail on A5 shows a transition strip type not listed in the schedule. Two exam rooms have no finish tag at all.

From one read-through, before any counting, the estimator has found four cost items (moisture testing, floor prep, integral cove, a special transition), one missing-information question (the untagged rooms), and the fact that scale differs between A1 and A2. Each would have been easy to miss by jumping straight to measuring square footage.

When drawings and specs disagree

Conflicts are normal. The plan shows one fixture and the schedule another, or the spec calls for a heavier gauge than the detail. Many contracts include an order-of-precedence clause that says which document governs, so check the general and supplemental conditions. On bid day, if the conflict cannot be resolved by RFI in time, price the more expensive option or state clearly which one you carried. Guessing the cheaper one and hoping is how a low bid becomes a losing job.

Mistakes estimators make reading plans

  1. Measuring before reading. Takeoff without the notes and specs misses scope that never appears as a line on a plan.
  2. Trusting PDF scale. Verify scale against a known dimension on every sheet.
  3. Reading only your discipline. Your scope can hide on another trade's sheets.
  4. Ignoring "by others" and "N.I.C." notes. Not in contract means someone else carries it. Confirm who.
  5. Missing addenda. A reissued sheet changes quantities and scope.
  6. Not writing questions down. A gap noticed but not documented becomes a scope gap after award.

From plans to estimate

Once the read-through is done, move to counting and pricing: see how to estimate a construction project and the construction estimate template. Keep your marked-up set with the estimate, because it shows the project team exactly what was priced. Smart Business Automator stores drawings, RFIs, and estimates with each job and can pull data from project documents, and won bids move into active projects through estimate to project handoff automation.

Frequently asked questions

What order should I read construction plans in?

Sheet index and addenda first, then general notes and legends, then the specifications for your scope, then floor plans, followed by sections, details, schedules, and other disciplines' sheets.

What is the difference between drawings and specifications?

Drawings show location, size, and quantity. Specifications describe quality, products, installation standards, testing, and submittals. Contracts often state which governs if they conflict, so check the general conditions.

How do I read a detail callout like 3/A502?

The top number is the detail number and the bottom or second part is the sheet. So 3/A502 means detail 3 on sheet A502.

Can I measure directly from a PDF?

Yes, with takeoff software or a calibrated PDF tool, but always calibrate scale against a printed dimension first. PDFs are not always plotted at true scale.

Written and edited by

Maurice Francois writes and edits construction operations guides for Smart Business Automator. More from Maurice on the Scaling Legends podcast.

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