What is an anchor bolt as-built survey?
An anchor bolt as-built survey measures the true, in-place position of anchor bolts after the concrete is poured, so those field coordinates can be compared against the design plans. On prefabricated structures — steel buildings, bridges, cell towers, and heavy industrial equipment — the steel is fabricated off-site to exact dimensions. If the bolts in the field don't match the plan, the steel won't seat correctly, and the fix is costly: re-fabrication, field modifications, or schedule delays. The as-built survey is the checkpoint that catches those problems before steel is ever cut.
When the survey happens
The as-built is performed after the pour has cured enough to work around and before the fabricated steel arrives. On large foundations there may be hundreds or even thousands of bolts to locate, so a repeatable, efficient workflow matters as much as raw accuracy.
Equipment you'll need
- A total station or robotic total station tied to a known control network
- A mini-prism on a pole or a fixed prism mount
- Established site control points with verified closure
- A reliable method for locating the true center of each bolt — this is where most error creeps in
Step-by-step workflow
- Verify your control. Confirm your control network closes to the standard your client requires — structural foundations often call for First Order, Class I (1:100,000) relative closure. Bad control invalidates every point that follows.
- Set up and back-sight. Occupy a control point, back-sight a second, and check against a third known point before collecting production data.
- Locate each bolt's center. Position your prism directly over the true center of the bolt where it exits the concrete. On a straight, plumb bolt this is simple; on a bent or leaning bolt it is not, and eyeballing it introduces error.
- Confirm plumb. Make sure your prism represents the true center point, not an offset caused by a tilted pole or a leaning bolt.
- Record and label. Store each point with a clear identifier that maps back to the bolt pattern on the plan.
- QA before you leave. Re-check a few points and confirm your setup hasn't drifted. Catching an error on-site is free; catching it in the office means a return trip.
Where accuracy is won or lost
The single biggest source of error in an anchor bolt as-built is the center-point call on bolts that are bent, leaning, or damaged after installation. When a crew eyeballs the center and plumbs the rod at the same time, two people can pick two different points on the same bolt. Those small differences don't show up until the raw data reaches the office — and by then the crew has left the site.
How a locating jig improves accuracy
A dedicated locating jig removes the guesswork by giving every crew member the same fixed, repeatable reference for dead center. The SDCJ Anchor Bolt Locating Jig slides over the bolt, references the true center where it exits the concrete rather than following the lean of the bolt, and uses an included laser plummet to confirm plumb before you store the location. It adjusts for bolts from ½" to 2" in diameter and mounts a standard mini-prism, so it drops into the workflow you already run.
Built around a 6061-T6 aluminum body and made in the USA, the SDCJ is engineered to support First Order, Class I standards on structural foundations. See the full specs and pricing →