How long does a GPR survey take

“How long will the survey take?” is one of the first questions on any GPR scanning enquiry. The honest answer is “it depends” — but the dependence is on a small number of factors, and once you understand them, the time on site is reasonably predictable. Here is what drives it.

The drivers

Time on site is driven by:

• Area to be scanned. Square metres of slab, wall, or floor. The single largest driver.
• Density of scanning. Fine grids take longer than coarse ones. PT detection requires a denser pattern than basic pre-drill clearance.
• Element type. A horizontal slab is faster than a vertical wall is faster than an awkward soffit.
• Access. Open access is fast; constrained or high-level access is slower.
• Surface condition. Clean, accessible surfaces scan fastest. Painted, tiled, or contaminated surfaces are slower.
• Number of elements. Multiple elements add mobilisation and documentation time on top of pure scan time.
• Reporting scope. The on-site time is one component; the reporting and CAD work is another.

A surveyor with the right information can quote site time tightly.

Typical durations

A short tour of typical site times:

A simple pre-drill scan, 5–10 small target areas on one slab. 1–2 hours on site, plus travel and reporting. Often quoted as a half-day attendance.

A reinforcement mapping survey of a typical slab area (say 50–100 m²). 3–5 hours on site, with the on-slab markup completed before the surveyor leaves. Typically a half- to full-day job.

A PT scan over a similar area. Longer than equivalent reinforcement mapping because the scanning density is higher and the interpretation is more careful. Typically a full-day job.

Reinforcement mapping of a multi-element campaign (several columns, beams, walls). 1–2 full days, depending on scope.

Large-scale GPR on a site (say 1–2 hectares with a vehicle-towed array). A single day for the field work, with processing and interpretation following.

Façade LiDAR with paired GPR investigation. Multi-day, often with several site visits.

These are indicative; specific projects vary.

Reporting time

The on-site time is one part of the picture. The other is the reporting time:

• Same-day on-slab markup. Always part of the deliverable on pre-drill work. The surveyor leaves with markings in place.
• Next-morning written report. Standard for most jobs. The surveyor returns to the office, writes up the data, and delivers the report within a working day.
• Multi-day reporting. For larger or more complex jobs (PAS 128 deliverables, integrated multi-method campaigns), reporting takes longer.
• Same-day report on request. Sometimes available for an additional charge or for jobs where the surveyor has time to write up before leaving site.

A reasonable expectation for a typical pre-drill or reinforcement-mapping job is on-slab markup the same day, written report the next morning, CAD plan within a working day or two.

Factors that compress the timeline

You can shorten the time on site by:

• Preparing the surface. Clean, accessible surfaces are faster to scan.
• Marking up the brief in advance. Drilling positions, areas of interest, and reference points all marked on the slab when the surveyor arrives.
• Providing site induction in advance. The half-hour induction repeated for each visit adds up; pre-induction saves it.
• Combining adjacent work. A single attendance that covers several scopes is more efficient than multiple visits.
• Specifying scope tightly. A clear brief is faster to execute than a vague one.

Factors that extend the timeline

Common reasons survey time stretches:

• Surface preparation done on the day. Cleaning slabs adds time that should have been done before attendance.
• Brief unclear or shifting. Re-scoping on site adds time. Lock the brief before attendance.
• Access not ready. Lifts, MEWPs, or scaffolding not booked or not in position.
• Findings prompt additional scope. A surveyor who finds an unexpected anomaly may need to extend coverage. This is honest expansion of scope; it should be agreed and quoted on the spot.
• Reporting requirements add up. Multi-format deliverables, BIM integration, multi-stakeholder review — all add reporting time.

A useful rule of thumb

For most concrete scanning work, the rule of thumb is:

• Half-day attendance for a small, focused job.
• Full-day attendance for a typical reinforcement-mapping or PT-detection scope.
• Multi-day attendance for site-scale work, multi-element campaigns, or paired-method work.

Reporting follows attendance by one to two working days for a typical job.

What to plan for

If you are programming GPR scanning into a project:

1. Slot a half-day or full-day on-site, depending on scope.
2. Allow one to two working days for reporting before downstream work depends on the report.
3. Build in a contingency for findings that prompt extended coverage.
4. Plan access ready for the day — the survey time is wasted if the access is not.

For pre-drill work specifically, schedule the survey to be complete and signed off before the drilling team arrives. Building drilling on the same day as scanning is rarely efficient unless the survey window has a defensible buffer.

The honest summary

A GPR survey is usually faster than expected by buyers commissioning their first one. A pre-drill scan of a typical area takes hours, not days. A reinforcement-mapping survey of a typical slab takes a working day, not a week. A reporting deliverable is in your inbox the morning after, not a fortnight later. The work is well-paced because the techniques are mature and the surveyors who do it are experienced. Plan accordingly.