In renovation projects, two realities meet: what was planned, and what was actually built. The two rarely match — and that gap is precisely why so many renovations run into cost overruns, downtime or structural queries mid-execution. The terms for this are as-designed and as-built. Anyone working in renovation should not treat them as synonyms.
Four terms, four life-cycle phases
A building passes through several documented states — and each has its own technical term. These four are the most common in the DACH region (Germany, Austria, Switzerland):
| Term | Life-cycle phase | What it describes |
|---|---|---|
| As-designed | Design phase | The intended target state. Architectural and consultant drawings, permit and construction drawings. What was supposed to be built. |
| As-constructed | During construction | An interim state. Red-pen corrections in the site diary, changed detail points, re-routed services — usually not yet rolled back into the drawings. |
| As-built | After completion | The actual state at completion or at survey. Dimensioned, documented, ideally backed by point cloud and 2D/3D plan. |
| As-maintained | In operation | Continuously updated as-built after conversions, maintenance, tenant fit-outs. Mandatory in FM models and CAFM systems. |
The transitions are fluid, but for renovation two columns matter most: what was planned (as-designed) and what is standing today (as-built). Everything in between has to be reconstructed — or surveyed.
Why as-designed rarely matches the actual state
Anyone pulling an old building file from the planning archive holds as-designed in 95% of cases, not as-built. The reasons are mundane and systematic:
- Drawings are produced before construction starts — changes on site only flow back if someone updates the records afterwards. In the DACH region, that was the absolute exception until well into the 2000s.
- Changes of use, tenant fit-outs, heating or electrical upgrades over a 30+ year horizon often never make it into the building files at all.
- Structurally relevant interventions — a removed internal wall, an added door, a newly cut lintel opening — are undocumented in many existing buildings, even when they were approved at the time.
- Post-war files frequently show nominal dimensions ("24-cm wall"), while the actual wall measures 26, 28 or 30 cm — depending on plaster, secondary linings and later overlays.
The consequence: anyone planning against the old building file is planning against a target state that no longer exists in the building. That becomes obvious at the latest when the first core drillings are taken or walls are opened up.
Where the deviations typically sit
Across more than 200 existing-building surveys, six recurring deviation patterns have emerged:
- Wall thicknesses are off. Plan says 24 cm, reality is 28 cm — relevant for lintel lengths, door frames, radiator niches and every connection detail.
- Lintel heights and sill heights vary. Especially in older buildings where windows have been replaced over the decades, clear dimensions rarely match the plan.
- Connection details are built differently. Classic case: the plan shows a clean wall-ceiling junction, but in reality there is a shadow gap or a moulding that becomes critical for the new acoustic ceiling.
- Material and layer build-ups are undocumented. Screed thicknesses, build-up heights, insulation layers — almost never identical to the plan, often altered later.
- Service routes are no longer traceable. Electricity, water, heating, ventilation — particularly in buildings with several renovation layers, the existing drawings should be assumed to be incomplete.
- Undocumented structural interventions. Internal walls that were "just removed" in the 1980s, beams without a structural calculation, openings added later. In renovation, this leads in the worst case to emergency structural securing during the construction phase.
How a serious as-built survey is produced
An as-built documentation that is genuinely usable for designers, structural engineers and energy consultants is based today on three techniques — individually or combined:
- LiDAR scanning. We use Matterport Pro3 or terrestrial scanners (Faro/Leica). Accuracy from ±2 cm per 10 m to ±2 mm per 10 m, depending on the method. The point cloud is the authoritative basis — everything else is derived from it.
- Photogrammetry. For facades, courtyards and areas that are awkward to reach with a LiDAR scanner. Also important in heritage work because textures are captured along the way.
- Hybrid capture. The norm in renovation: LiDAR indoors, drone with RTK outside, occasional handheld scanner for structurally or heritage-critical details. The three data sources are merged into a consistent existing-building model.
An important distinction: an as-built survey is not the same as classical measuring. Classical measuring means individual dimension chains with folding rule or laser distance meter — fine for a single wall, but unsuitable for an entire storey with complex geometry. A modern as-built survey captures everything visible in a single pass. Whether you later need only the floor plan or every socket is a decision made at the desk — not on site.
What you actually receive
From a single survey we deliver up to four output tiers, typically staged:
- Point cloud (E57, RCP, LAS). The raw data. Directly usable in Revit, ArchiCAD, Allplan, AutoCAD. For designers who prefer to draw up the rest themselves.
- 2D as-built drawings (DWG, PDF). Floor plans, sections, elevations — derived directly from the point cloud, dimensioned to specification. The typical deliverable for renovation and permit drawings.
- 3D model (IFC, FBX, Revit). Polygonal model with walls, ceilings, openings, stairs. Suitable for visualisation, energy consulting, room books.
- BIM as-built model (LOD 200–300). Parametric model with components, attributes and layer build-ups. More effort up front, but usable across the full life cycle — mandatory for many public tenders.
More on this last tier in our article on digital twins from point clouds in existing buildings.
The cost of not surveying the existing fabric
The temptation to skip an as-built survey is understandable — but it rarely pays off economically. Three scenarios we see repeatedly:
- Site shutdown for structural query. If, during wall demolition, a load-bearing element appears that was not on the plan, the site stops until the structural engineer has re-assessed. Downtime costs of €800–2,000 per day are not unusual.
- Mid-flight design change. If the wall thickness is wrong, the new bathroom doesn't fit — tiles need to be re-calculated, sanitary fittings re-ordered, door frames re-worked. A 5–10% cost surcharge on the affected trade is a realistic figure.
- Fire-safety and energy (EnEV/GEG) certificates. Above a certain renovation scope, building authorities require evidence of the existing state. A complete as-built saves the energy consultant the entire survey effort, often three to four times the cost of the original capture.
The rule of thumb from our projects: an as-built survey typically costs 0.3–1.2% of the renovation budget. The first avoided site shutdown usually pays for it.
Insurance and permits
Two aspects are often underestimated in practice. First, the insurance side: anyone renovating without a documented existing state who causes a structural incident has a problem with their builder's liability insurance. Second, permitting practice: fire-safety concepts, GEG evidence and heritage statements all require a defensible record of the current state. Drawings from 1962 no longer satisfy most authorities.
Conclusion
As-designed describes an intention, as-built describes reality. In new-build projects the gap is small. In renovation — especially in buildings from the 1950s to the 1990s — it is the single biggest risk factor of the entire project. A modern as-built survey with point cloud, derived 2D drawings and optionally a BIM model closes that gap in 1–3 days of on-site capture and 1–2 weeks of post-processing. The investment pays back not over the life cycle, but almost always within the very first renovation phase.
If you have a concrete renovation project ahead and are unsure how much as-built depth you actually need: an initial assessment costs nothing.
We capture the actual state before you design.
LiDAR scan, point cloud, 2D drawings and, on request, a BIM as-built model. 1–3 days on site, post-processing from 2 weeks.
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