How to scan old house plans for a 3D model

Conceptual model only. Not a survey or construction document.

Which sheet in an old architect’s set to scan, how to photograph it so the dimension strings survive, and what the drawing no longer describes.

Scan the floor plan sheet itself: lay the paper flat, shoot or scan it square on with the whole sheet in frame, and save it as a PDF or PNG rather than as a sharpened photo. Legible room boundaries, opening symbols, and dimensions help the reconstruction; lost detail can cause missing or incorrect geometry. A set from an architect or a builder is several sheets, and only one of them is the sheet you want, so sort the folder before you photograph anything. This page is for a homeowner or a contractor holding an old set and wondering what is still true.

Which sheet in the set do you scan?

Spread the folder on a table and look for the floor plan: the sheet drawn as if the roof had been lifted off, with room names written inside the walls and dimension strings running along the outside edges. Sections, elevations, foundation details, and the electrical layout are worth keeping in the folder, but none of them describes a room you can walk through. If the house has two stories, they are two sheets, and you upload one file at a time, so start with the floor you actually want to see. The PDF floor plan route covers preparing a one-page PDF and providing drawing context for scale interpretation.

If you grew up calling the whole set blueprints, that name came from a printing process that put white lines on blue paper. What is in most drawers today is a black line print, or a photocopy of one, and either works as a source while the lines are still crisp.

What does the title block tell you?

Every issued sheet carries a title block, the ruled panel usually in the bottom right corner. It holds the scale, the date, the sheet number, and the revision letter. Check that the sheets you keep all carry the same revision, because a folder assembled from two issues describes two different houses. A sheet marked as built or record drawing describes what was constructed. A sheet marked for permit, for bid, or preliminary describes what was intended, and intentions change on site. The scale printed in the block matters less than people expect: a photocopy, or a reduction from a large sheet to a small one, changes the ratio while leaving the printed numbers correct. So when a dimension printed on the drawing and a measurement off your ruler disagree, believe the printed dimension. If your only copy is a PDF and you need one number out of it today, measuring a floor plan from a PDF covers the manual route. If the sheet carries no dimensions anywhere, you are reading it the way you would read a builder’s floor plan, and the same caution applies.

How do you scan or photograph a large old plan?

• Lay the sheet flat and weight the corners. A rolled drawing photographs with bowed walls, and the bow ends up in the lines the model is built from.
• Keep the whole sheet in frame. The app’s own guidance is to use a clear, uncropped plan with room boundaries and dimensions where available, and the dimension strings at the edges are exactly what a tidy crop removes.
• Shoot square on, with the camera parallel to the paper and centered over the sheet. A photo taken from an angle turns a rectangular room into a trapezoid.
• Light the sheet evenly. Skip the flash, work near a window or under room lights, and keep your own shadow off the paper.
• Scan at 300 dpi or better if you have a scanner, and do not sharpen, auto-enhance, or force the image to pure black and white. Thin lines and small dimension text are the first things those filters lose.
• For a single-floor upload, extract the required sheet as its own one-page PDF before uploading. The single-floor flow reads the first PDF page; the drawing-context page number records the source sheet and is not a page selector. For several floors, Business lets you select a drawing or PDF page for each floor in the building flow.
• The app takes PDF, PNG, JPEG, SVG, or DXF, up to 25 MiB. If the drawing also exists as a DXF, send that instead of a picture of a print.
• A sheet larger than your scanner is worth carrying to a copy shop with a wide-format scanner. If you photograph it instead, capture it in one frame rather than stitching two halves together.
• Enter dimensions you can verify. The upload accepts drawing units, a scale denominator, and up to 30 reference measurements, each a label plus a known length. These help interpret scale; one measurement does not establish that a faded print or its reconstructed rooms are accurate. Check the reported scale status and compare a second independent dimension in another part of the model.
• Use a neutral project name you will recognize later, such as Upstairs layout study. Names run up to 120 characters. A published project title is public, so do not put an address, client name, or other identifying detail in it unless you intend to publish that information.

NoteThe app asks you to upload only a floorplan you have permission to use. An architect’s drawing is usually the architect’s work even when the house is yours, so that line is worth reading before you publish anything built from it or pass it to someone else.

What does an old drawing no longer describe?

A drawing describes the building on the day it was issued, and the longer it sat in the drawer the more of that description has moved. Areas are the clearest case. The reference plan above prints LIVING 30.0 m² inside one room, about 323 sq ft, which is what the person who drew it calculated from those lines. A model built from the same sheet reports a modeled floor area, a space count and per-space dimensions, and those numbers rarely land in the same place as the printed ones. Why your floor plan and 3D model disagree on square footage takes that apart. Also check for changes made since the drawing was issued before ordering materials.

Worth checkingAn old drawing does not know what happened after it was filed, and a model built from it inherits every difference, because the conversion includes no site visit. The reconstruction can also misread the drawing itself. Before you rely on it, take a tape to two things: one long run across the plan, and the room you intend to change. Use this model for design exploration. Verify dimensions on site before ordering or building.

What we build from an old drawing, and what we do not

You create a project, which keeps one home’s floorplan and its model together, and you upload one sheet. The file is checked before anything is built from it. The service reads the plan, traces the walls and rooms, closes the gaps, and raises a 3D model you can open in a browser; floor plan to 3D is the short description of that conversion. The workspace shows which processing steps have finished rather than how long is left, so you can close the tab and come back. When the model is ready, the viewer reports a modeled floor area, a space count, the overall extent and the model height, in meters, and 1 m is about 3 ft 3 in.

What it does not do matters more with an old sheet than with a new one. Nobody visits the property, so everything the model knows came off the drawing you sent. It reads a floorplan, not a section, an elevation, or an electrical sheet. Business includes multi-floor building reconstruction: choose a source drawing or PDF page for each floor and review alignment, elevations and stair connections before confirming. The workspace also tells you whether the drawing’s scale resolved, and on a faded print or a heavy reduction it may not. You can change furniture and finishes and keep them in a separate design option, but the walls stay where the drawing put them, because the reconstruction is locked and not editable. Every model carries the line the app prints beneath it: Conceptual model only. Not a survey or construction document. That matters most when the next person to hold your drawing is a contractor. Projects become public only when you publish a release; the uploaded source drawing is not part of the public project page. One import converts one plan, and Free covers a single lifetime import of a public project, with the rest on pricing. If the plan in the drawer is the start of a renovation, renovation planning sets out what the model gives you and what it leaves to you.