From Measured Survey to As-Built Drawings: A Practical Workflow.

Decide what the survey is, before you open any software

A measured survey is a time-stamped record of existing conditions. It is not a compliance certificate, and it does not become one because the linework is tidy. Hold that thought through the whole workflow, because it governs how you label drawings, what you promise a client and what you log when something does not add up. Before any import, sort what you have been given into three piles. Each enters the workflow differently. DWG is AutoCAD's native format. DXF is the more exchange-oriented cousin. Survey practices commonly supply layered DWG, and where a model has been commissioned for coordination, IFC sits alongside Revit deliverables at a level of information the employer's requirements define. Point clouds are also offered next to DWG, IFC and PDF by as-built survey providers, so your starting evidence may be scan-derived rather than line-based. The same discipline applies either way: know what you are holding before you build on it. ### Check units, origin and orientation first Undeclared units are the commonest reason a plan lands at the wrong size. UK survey suppliers report that architectural survey drawings are often produced in metres, sometimes to three decimal places. A dimension style that displays millimetres does not prove the underlying units are millimetres. Before tracing anything, confirm units, origin and orientation, then check one known dimension, a door opening or a long measured wall, against your site notes. ### Agree the end product up front A small rear extension may need existing plans, sections and elevations at 1:50 or 1:100, the scales survey providers commonly issue at. A refurbishment or coordination package may need a fuller existing-conditions model. These are different jobs with different effort. Settle which one you are doing before modelling starts, and record the survey date, inaccessible areas, assumptions and unresolved discrepancies from day one. ## Get the surveyor's file into Linea and crop it to one plan Import the DXF or DWG into Linea, the browser-based drawing and modelling studio on ArchAdemia Tools. The import dialog draws the file before it lands, so you see what you actually have before committing to it. That preview is worth a minute of attention. It is where a file in the wrong units or with stray linework far from the origin shows itself. Practice CAD files frequently hold twenty-odd drawings in one model space, all on shared layers. Ticking layers cannot isolate the ground-floor plan from the first-floor plan when both sit on the same layer names. The import dialog finds the separate drawings and outlines them. Click one, or drag your own box where detection misses, and the import crops to that single plan, cut clean at the edge and landing on the origin. ### One import per level Repeat the crop for each floor, importing the same file once per level. Every plan lands on the origin, so the storeys line up without manual nudging. This is faster and more reliable than copying linework between files, and it keeps each level traceable back to the same source. ### If the surveyor sent an IFC Import that instead. A native IFC is parsed in the browser with nothing uploaded, which matters when the survey sits under a confidentiality clause. Surveys can contain commercially or security-sensitive information, so check what your instructions and any data-handling agreement require before the file goes anywhere. Treat any tool's privacy behaviour as something to confirm against its own documentation, not as something to assume. ### The first sanity check Measure a known dimension against your own site notes before you build on the file. A door set or a long wall is ideal. If the file reads 1,980mm for a door you measured at 1,980mm, carry on. If it reads 1.98 or 19,800, stop and sort out the units now. Ten seconds here saves you rebuilding a floor later. ## Rebuild the building as a 2D plan and a 3D model together With clean reference geometry in place, trace over it with parametric walls, doors, windows, stairs, slabs and roofs. In Linea the plan and the 3D model are the same building edited together, not one generated from the other. Correct a wall thickness on the plan and it is corrected in the model. That propagation is the point: sections and elevations cut from the same model stay consistent with the plan, rather than being redrawn separately and drifting apart. ### Levels and exact values Stack the levels into storeys and set floor-to-floor heights from your site notes. Type exact values rather than dragging. Start typing a number mid-gesture and it lands in a box beside the cursor. Press Enter to apply it, and Tab to step between values when a gesture takes more than one. Lengths read in the drawing's own units, so 1200mm and 6ft both parse. For survey work this matters: a wall drawn to a typed 215mm is a wall you can defend, where one dragged until it looks right is not. ### Irregular buildings: block out first Where the building is irregular, use the Massing workspace first. Block out the footprint and roof form quickly, then switch to Build for detailed walls and openings. An out-of-square Victorian rear return with a pitched lean-to is far easier to establish as massing than to wrestle into walls on the first pass. ### Keep survey evidence apart from interpretation Awkward existing features, such as a boundary wall, a lean-to or a rooflight, are best drawn as model lines and detail lines on named layers. That keeps survey information separate from your own interpretation. Name the layers plainly: measured, assumed, inaccessible. A reader scanning the drawing should be able to tell at a glance which geometry was observed and which was inferred. New geometry in Linea starts as a flat colour: white walls, light grey floors and roofs. Finishes appear only where you paint them. That suits an existing-conditions model, which should read as a record of form and not as invented materials. ## Cut sections and elevations, then reconcile against the site A survey is not finished when the imported plan looks tidy. Cut sections and elevations from the model as real linework, then compare them against your photographs, hand notes and recorded levels. This is where assumptions get exposed. A section that disagrees with a site photo is a measurement to re-check, not a drawing to tidy. Resist the urge to quietly nudge a level until the section looks right. A disagreement is a prompt to go back to the evidence, and if the evidence cannot resolve it, the honest next step is another site measurement. ### Save the views you issue Save the sections and elevations you issue. When the model changes after a second site visit, you reissue the same views rather than redrawing them. On a project with two or three rounds of corrections, this is the difference between a ten-minute update and an afternoon. ### Ask Corb, then check Corb, the assistant chip beside the 2D/3D toggle in Linea, answers questions about the drawing for free, such as what a particular stair rise comes to. Treat any answer as a prompt to check, never a verdict. If a figure is missing from the model, Corb will not invent one, and neither should you. The next step is a tape measure. ### Calibrating a photographed sketch For a photographed site sketch, place it as a trace guide. On a phone it opens uncalibrated until someone sets a real-world length on desktop, so calibrate it before you draw from it. An uncalibrated sketch is a picture, not a measurement. A hand-drawn plan of a loft conversion photographed at an angle can be badly distorted, so calibrate against a dimension you trust and treat the result as evidence to be cross-checked. ### Keep a discrepancy log Keep a short list on the sheet or in your project notes. Typical entries:

• Party wall out of square by a stated amount
• First-floor level assumed, not measured
• Rear bedroom not accessed on survey day
• Roof structure and foundation conditions unverified

That list is what protects you when someone asks, months later, why the as-built set differs from what they found on site. ## Sheet it at true scale and send it out Export each drawing sheet from Linea as a PDF at a true plotted scale on your chosen paper size, with a title block. Choose the sheet size from the scale you need. A 1:50 plan of a small house and a 1:100 site plan are not the same sheet: the 1:50 plan needs materially more paper. Check the exported PDF at true sheet dimensions rather than trusting the on-screen view, and make sure the title block identifies project, drawing status, survey date, scale and revision. ### Finishing by hand If the issued set needs finishing, export DXF and use Open in Vector to bring it in as editable linework. Vector is the studio for architect-scoped vector drawing. Set the real-world scale, add annotation and a regenerated scale bar, then export a PDF, SVG or DXF. The scale bar regenerates whenever the scale changes, so it cannot silently disagree with the drawing after a vector conversion. Check it anyway. ### The client or planning pack For a client or planning pack, assemble plans, sections and photographs in Layout as a Document at A3 and export a vector PDF at true sheet dimensions. A short existing-conditions section in a Design and Access Statement is the usual place this lands: a few plans, the key section, annotated photographs and a plain statement of what was surveyed and when. Layout is available on every plan, and manual layout work costs no credits. ### Close the loop with the surveyor Send the DXF back for a markup check. This is the cheapest quality control in the whole workflow. The surveyor confirms the as-built set against the original measurements, rather than your reading of them, and any disagreement surfaces before the drawings reach a client or a planning officer. ### Where this workflow earns its keep The same sequence serves a conservation recording job, a fit-out base drawing, an accessibility study, a façade analysis, a competition entry on an existing site or a portfolio piece built on a measured building. The survey input changes. The discipline does not: identify what you hold, import it cleanly, rebuild it as one model, reconcile it against the site, and issue it at true scale with its limits stated. ## The takeaway Treat the survey as evidence and the drawing as a record. Sort your inputs, confirm units against a dimension you know, crop each level cleanly, rebuild plan and model together, keep measured and assumed geometry visibly apart, and reconcile every section against the site before it leaves the office. Then label the sheet honestly: what was measured, when, and what was not seen.