Why the old plans drift
Slabs move. Structure gets added. Previous trades route around problems that nobody documented, and the as-builts were marked up by someone who was already on the next job. None of that is negligence; it is just what happens to a building over twenty years.
What a scan catches
- Tie-in points that are not where the drawing says they are.
- Structure and existing services that were never recorded.
- Ceiling heights and slab conditions that change what fits.
- Equipment clearances that only exist on paper.
The economics of finding it early
A scan is a fixed, known cost early in the job. A spool fabricated to the wrong dimension is an unknown cost late in the job, and it does not arrive alone: it comes with a schedule impact, a change order conversation and a crew standing still.
That asymmetry is the whole argument. You are trading a small certain number for a large uncertain one.
Sources
- Practice on renovation and tie-in work across NJ, NY and FL.