Scan-to-Estimate: From Site Capture to Quantity Takeoff

You can get a quantity takeoff from a 3D scan with no usable drawing in front of you: capture the space room by room, measure the areas, lengths, heights and openings off the model, then build the quantity sheet from those measurements with deductions and waste stated as rules. The scanning is the easy part. The work that decides whether the estimate holds up is choosing what to capture before you walk in, and measuring the same way twice.

Start at the site, not at the drawing

Most estimating assumes a drawing exists and can be trusted. On a renovation or addition that assumption is often wrong: the plan is from a previous owner, the extension was built without one, or the drawing shows a wall that came out years ago.

When the drawing is wrong, every quantity measured off it is wrong in the same direction, and the errors compound at each handoff. A scan changes which document the numbers come from. You measure the building, and the plan becomes a view of that measurement rather than a guess about it.

The limit is worth stating first. A scan only contains what you walked past and pointed the camera at, and Polycam builds the model from what you show it. Coverage is a decision made on site, not something the software repairs afterwards, which is why the capture plan comes before the capture.

The order below is the whole method: decide what to capture, capture it, measure it, sheet it, then name what the scan cannot answer.

Step 1: Decide what to capture, working back from the quantity sheet

Do this in the van, not in the room. List the line items you expect to price, then write down the measurement each one needs. Anything with no measurement attached is something you would price from memory later.

Two things fall out of it. First, the rooms you must capture: every room being altered, plus any room whose finishes, services or access the work affects. Second, the details a room-level scan can miss, such as opening sizes, reveal depths, the height under a beam, and the run lengths of joinery that stays.

For an addition, the junction decides the cost. Capture both sides of the wall being opened up, the floor and ceiling levels on each side, and the route from the street to the work area. Access and protection are quantities too.

Keep the list on your phone while you scan. It stops you leaving with a set of models that answer the easy questions and none of the ones the estimate turns on. The site survey workflow covers route planning and coverage in more detail if the visit itself is the weak point.

Step 2: Capture so the numbers survive the trip to the office

Capture in Space mode when you want the mesh as well as the plan, since the same walk returns a scaled floor plan and a 3D mesh. Walk the perimeter of each room rather than standing in the middle and turning. The wall faces, the floor line and the ceiling line are what the dimensions come from.

Open every door you intend to capture before you start, then walk one continuous route hugging the left wall. Polycam's own guidance is to allow about two minutes per hundred square feet, which is a realistic budget when you are costing your own time into the visit.

Capture what gets priced, not what photographs well

Furniture against a wall is the most common reason a room measures small, because the unit gets read as the wall line. Scan around its sides and above it so the wall behind is in the model. Where a fitted wardrobe or a kitchen run is staying, capture the full front, because its run length and depth are quantities.

Record the existing finishes room by room: floor covering, wall finish, ceiling type, whether there is a cornice or a coved edge. All of them change what strip-out and making good cost. The mesh shows the shape, the photos show the material.

Some of what an estimator needs never appears in geometry: boiler and appliance model plates, socket and switch positions, pipe runs behind units, the buildup at a window reveal. Virtual Walkthrough on a Space capture lets you retrace the walk and view the original photos where you took them, so those details stay readable after you leave the site.

Look at the generated plan before you walk out. A missed corner reads as a room that is too small, and rescanning takes a minute while you are still in the room.

Step 3: Measure areas, lengths, heights and openings off the model

Work in one order every time: areas, lengths, heights, openings. A fixed order makes two people's sheets comparable.

Areas

The capture returns floor area, perimeter, ceiling height and wall area for each room. Treat floor area as gross: it includes the footprint of everything standing on the floor, so a chimney breast, service void or built-in unit comes out before the figure is a finished floor area.

Wall area is the most abused number in a takeoff, because it is not the area you plaster. Openings and the areas above and below them are treated differently depending on what is being priced, so measure the openings and apply your own rule rather than accepting one net figure.

Lengths

Wall lengths in an older building are rarely identical at skirting height and at ceiling height, and a room that is out of square changes length depending on where you measure. Measure each run at a stated height and write that height down. For skirting, measure the base. For wall covering, measure at mid-height.

Take opening perimeters as well as widths, since trim and linings are priced around the opening. Sill height and reveal depth decide whether a window can be replaced without touching the internal finish.

Heights

Take floor to ceiling in every room, and floor to the underside of any beam or soffit that services pass under. A ceiling that steps by 200 mm changes the wall area, the door height and whether a standard sheet fits without a horizontal joint.

The measuring tool and the one check worth doing

The measuring tool gives the distance between any two points you pick, and on a Space or Floorplan capture the LiDAR sensor measures at real-world size, so there is no scale to set. Auto measure produces the dimensions for you on Space and Floorplan captures on the Business and Enterprise plans.

Then check one number by hand. Pick the wall you are pricing the most material against, measure it with a tape, and compare. It takes a minute and tells you whether this capture worked in this room, with this lighting and this furniture. If the two disagree, look at the plan before trusting either.

Step 4: Build the quantity sheet

One row per line item, one block per room or finish zone. The sheet is the only thing the estimator can price without calling you back.

Every row carries ten things: a reference and the line item; the room or zone; the gross quantity as measured; the deduction and the rule behind it; the net quantity; the waste percentage and why it was chosen; the order quantity rounded to the selling unit; the unit; the source; and a flag for priced, assumed or not priceable.

A worked line, using a real room. A bedroom measures 4.2 m by 3.6 m on the plan, which is 15.1 m². The chimney breast takes 0.6 m² off the floor, so the net floor area is 14.5 m². Its perimeter is 15.6 m, so at a 2.4 m ceiling the gross wall area is 37.4 m², less a 1.9 m² door and a 1.4 m² window, which leaves 34.1 m² of wall to finish.

That is the method. Gross from the model, deduction from a stated rule, net for the installer, waste for procurement. What keeps it an estimate rather than a calculation is the source and flag columns: a number with no source is an assumption, and assumptions belong in the flag, not among the measured quantities.

Step 5: Deductions and waste are method, not a magic number

Deductions go wrong when the rule is reinvented per line. Decide once whether you deduct openings at all, whether there is a size below which you ignore them, and whether you deduct the structural or clear opening. Write the rule at the top of the sheet and apply it on every line.

If the estimate will be priced to a formal method of measurement, use the estimator's rules rather than your own. A quantity that is right by your convention and wrong by theirs still produces a wrong price, and the argument happens after the bid is in.

Waste is not one percentage for the whole job. Published estimating references commonly give 5 to 15 percent, varying with the material and the cutting the layout needs, with sheet goods on flat surfaces at the low end and tile or patterned work at the high end. Tile is usually taken at about 10 percent on a straight grid and 15 to 20 percent on diagonal or curved layouts, and wood flooring moves from roughly 8 percent straight to around 15 percent laid diagonally.

Treat those as starting points. Your own job history is the better number, which is why the waste column records the figure and the reason. Round the result up to the selling unit: a box, a sheet, a full length.

Keep waste and contingency apart. Waste covers predictable cutting loss and breakage on a quantity you measured. Contingency covers what you have not measured or have not been told. Using one to hide the other means neither can be checked later.

Step 6: Flag what the scan cannot price, then hand it over

Part of the estimate never comes from geometry. A scan shows that a wall exists and how thick it is. It does not say whether it carries load, what is inside it, or whether the plaster behind the tiles is sound.

The list is short and predictable: structural adequacy, condition behind finishes, services capacity and routes, hazardous materials, access and scaffolding, the specification the client wants, and anything they have not decided. Each item goes on a not-priced list with the reason and the person who resolves it. Do not fold it into a percentage.

Send a package, not a file: the plan as DXF if the estimator works in CAD and PDF if they are quoting, the model as a link they can open in a browser without an account, the room areas as a CSV for their spreadsheet, the quantity sheet, and the not-priced list. Add capture notes: rooms covered, rooms locked, numbers checked with a tape. If the scan has to reach another office, the field-to-office handoff covers sync and versioning.

From there the work changes shape. Once the capture has become a plan that people are designing and pricing against, the next step is the plan-first sequence, from floor plan to estimate, where the takeoff is built from the drawing and its dimensions. If the estimator needs editable linework rather than a PDF, exporting the plan to DWG covers the format side.