TL;DR
Seven design risks follow bad as-builts: undeliverable ceiling heights, MEP routed into occupied plenum, structure sized to the wrong member, fabrication into an out-of-square building, code compliance claimed against unmeasured geometry, phasing on wrong areas, and consultants on different baselines. Exposure runs 15–40 RFIs at $1,200–$2,500 each and 3–8% change orders; a $0.25–$0.60/sq ft measured baseline cuts it to 2–8 RFIs.
Design teams inherit existing-conditions risk without pricing it. The drawings arrive, the schedule starts, and the assumption that the geometry is roughly right gets baked into decisions that become expensive to unwind.
Seven risks, in the order they typically bite.
1. Ceiling heights that cannot be delivered
Floor-to-deck heights get assumed uniform. They rarely are, especially in buildings with additions or in structures that settled. Design a 9'-0" finished ceiling against an assumed deck and the duct main will not fit above it. The discovery happens in coordination, after finishes, lighting, and sprinkler layouts are already committed to that height.
2. MEP routing designed into occupied plenum
The single largest source of existing-conditions rework. Record drawings show intent from the original build; three decades of retrofits are not on them. On a 220,000 sq ft plant retrofit, a scan-derived LOD 300 model found 143 pipe runs routed differently than the PDFs claimed and retired 26 potential RFIs, avoiding roughly $340,000 in rework.
3. Structure sized against the wrong member
Member sizes on legacy drawings are frequently the design size, not the delivered one — and at additions, two framing systems meet with neither drawing set showing the other. A retrofit connection designed to the wrong flange dimension comes back from the shop.
4. Millwork and glazing fabricated square into a building that is not
Historic masonry is never plumb or square. Anything fabricated off-site to a square assumption — storefront, casework, elevator enclosure — gets shimmed, re-cut, or remade. This risk lands entirely on the fabricator's schedule and the owner's budget.
5. Code compliance claimed against unmeasured geometry
Egress widths, ramp slopes, clearances, and headroom are all documented from the drawings unless someone measures them. On a 480,000 sq ft, twelve-building campus, the federated model built from measured geometry flagged 19 non-compliant curb ramps that the record documents showed as compliant.
6. Phasing plans built on wrong areas
Area takeoffs from unverified plans drive phasing, tenant scheduling, and revenue projections. A percentage error in the baseline propagates into every one of those, and it is discovered when a phase does not fit its space.
7. Consultants designing on different baselines
Architect on the 1978 set, MEP engineer on a 2011 tenant fit-out set, structural on field notes. Three baselines, none of them shared, all internally consistent. Federation exposes it, usually late.
What the exposure adds up to
Across renovation work with unverified conditions: 15–40 RFIs at $1,200–$2,500 each, change orders at 3–8% of contract value, and 10–20 days of schedule slip. The full breakdown is in the true cost of bad as-builts.
Against that exposure, a verified scan-and-model package runs $0.25–$0.60/sq ft all-in and drops the RFI count to 2–8 with change orders under 2%. Capture and registration alone, if a cloud is all you need, runs $0.05–$0.20/sq ft.
What changes when the design starts from measured geometry
- 96,400 sq ft warehouse conversion — 2.5 field days at ±6 mm, LOD 300 model in 18 business days, $85,000 of contingency released, 17 RFIs avoided, MEP coordination started three weeks early
- 38,400 sq ft active hospital wing — captured in two overnight shifts with no disruption to care, 23 RFIs avoided, $147,000 in change-order risk removed, design started 10 days early
- 180,000 sq ft across six connected historic buildings — LOD 300 Revit model in three weeks, hosted viewer replaced 14 planned site visits (about $18,000 in travel), measured baseline supported the tax credit submission
How to close the exposure
Capture runs 80,000–120,000 sq ft per day on open interiors and registers to ±5mm. Specify the deliverable properly — accuracy in millimetres, LOD by system, formats, unscanned areas listed, and an acceptance test — using how to write a scan deliverable spec and the scope of work template.
Services: As-Built Documentation, Scan to BIM, Building 3D Laser Scanning. Questions on a specific building: 614-210-3679.