In a brownfield retrofit, drawings describe the plant someone intended to build but not the one that exists today. Decades of undocumented modifications, sagging pipe racks, relocated cable trays and temporary fixes that became permanent, all sit between the design model and the steel your crew will bolt to.
As-built validation closes this gap before anything is fabricated or installed. It answers the question: "Can the new design be installed in the space that actually exists, within the tolerances, without surprises on shutdown day?"
Getting it wrong is expensive. Prefabricated spools that don't fit, extended outage windows, and hote work in live process areas all trace back to an as-built assumption nobody checked.
If you're a BIM Manager, VDC team or engineering lead responsible for a retrofit, this guide walks through the five questions to answer before installation begins, expanding on our guides: building a cloud scan-to-BIM workflow and comparing 3D models to as-built reality.
Not everything needs to be scanned but everywhere that the new work touches.
Start from the retrofit design and ask three simple questions:
These connection points deserve the most attention because just a few centimeters out and delays and rework ensues.
Before anyone draws conclusions from the scan data, make sure it's complete and sitting in the right place.
Complete means no blind spots in the areas that matter. Busy plant rooms are full of hiding places, like behind tanks, on top of pipe racks and above ceilings. If a connection point isn't clearly visible in the scans, it hasn't been properly checked.
In the right place means the scans and the model line up properly. If they're even slightly misaligned, everything will look wrong, and real problems become impossible to spot. A quick sense check is to look at things you know haven't moved, like columns or floor slabs, and if these match, you're on track.
Not every difference matters. A duct that's 20mm off in an open ceiling voice is rarely a problem, A pipe connection that's 20mm off can mean a re-fabricated spool and a delayed shutdown.
Agree with your design and installation teams what "close enough" means for each type of work before the review starts. Focus the tightest standards on connections and tight spaces and be more relaxed elsewhere. Writing these limits down means everyone judges the results the same way.
This is where scans and models come together.
First, compare the existing model with the scans to see where reality has drifted. In Cintoo, the comparison tools colour the differences so problem areas stand out at a glance, and anything inside your agreed limits can be passed quickly.
Second, drop the new design into the scanned space and look for anything in the way. Think beyond simple collisions - does the crew have room to lift, turn and bolt things into place; is there space for insulation, maintenance and safe access; will the largest piece fit through the door etc.
For every issue found, decide what happens next. Accept it, update the model, change the design, sort it on site or re-scan. Then give it an owner so it doesn't get missed,
Validation is only useful if the people on site can see the results and trust them.
Give the installation team a clear, simple package: what was checked and when, what was found, what was fixed, and what they still need to watch for on site. Include clear images of every connection point. Even better, give them access to the scans and model in a web browser so they can look and measure for themselves.
Finally, plan to scan again once the work is done. It confirms the installation matches the plan and leaves the owner with an up-to-date record for the next project.
Retrofits rarely go wrong because of the new design but more often because something about the existing site that wasn't checked. Answering these five questions before installation turns guesswork into proof your team, client and schedule can rely on.
Cintoo brings your scans, models and comparison tools together in one place, accessed easily via a web browser, so everyone works form the same picture of reality.
See how teams use it to reduce risk in brownfield and retrofit projects or try it free with your own scan data.