Setting Out & Survey Control

Benchmarks, grids and datums — the invisible framework every trade builds to.

Last updated 2026-07-28 by the BuildPedia Editorial Team.

What is Setting Out & Survey Control?

Setting out is the translation of drawings into physical points on the ground, and it underpins literally everything that follows. Get the control wrong and every trade downstream builds faithfully to the wrong position — I have seen a house built 300 mm off its footprint because a single reference peg was knocked and re-driven by guesswork.

Good survey control is hierarchical: primary control stations fixed and protected off the working areas, secondary stations and benchmarks distributed around the site, then the working grid lines, offsets and level datums the trades actually use. Every point is established from at least two independent observations, checked by a second person, and recorded so it can be re-established when — not if — a peg gets run over.

When and why is Setting Out & Survey Control used?

Primary control goes in immediately after site clearance and before earthworks, because excavation destroys the very ground the design was drawn against. It is then re-verified at every stage: before blinding, before reinforcement, before frame erection, and finally as an as-built record at handover. It matters because position and level errors found late are among the most expensive defects in construction — foundations cannot simply be moved. On a single house the hierarchy shrinks to a benchmark, two profile boards and a dumpy level — but the rule that every point is checked by a second person before concrete is exactly the one that protects the domestic job, because there is no survey department to catch the mistake.

Types of Setting Out & Survey Control

Total station (traverse) control

A total station measures angles and distances between intervisible control stations to millimetre precision. It is the workhorse for building sites: accurate, independent of satellite coverage, and equally good for setting out and for as-built checks.

GNSS (RTK) control

Real-time kinematic GPS gives centimetre-level positions anywhere with sky view, using a base station or network corrections. Ideal for large open sites and earthworks, less reliable between tall structures or under tree canopy where signals drop.

Traditional optical methods

Dumpy and laser levels for level transfer, theodolites and tapes for lines, 3-4-5 triangles for right angles. Still the everyday tools for transferring levels to pegs and checking short dimensions — and the essential fallback when batteries die.

Setting Out & Survey Control: step by step

Step 1: Establish primary control stations

Establish primary control stations — Setting Out & Survey Control, step 1

Fix three or more primary stations in stable ground outside all working areas — typically steel pins in concrete or survey nails in existing hard surfaces. Observe them by total station traverse or GNSS and adjust the network by least squares. These stations outlive the project, so protect them with fencing and paint, and record them on the control drawing.

Step 2: Establish the site datum and benchmarks

Establish the site datum and benchmarks — Setting Out & Survey Control, step 2

Tie the site datum to Ordnance Datum Newlyn — UK levels quoted in metres above Ordnance Datum (mAOD) — or to the project datum stated on the drawings, by levelling from a known benchmark. In the UAE, levels tie to the Dubai Municipality datum; whichever datum is used it is stated on every drawing, and datums are never mixed. Install at least two site benchmarks, independent of each other, and level between them to close the loop. Every level on site — dig depths, slab levels, drainage inverts — traces back to these points.

Step 3: Compute and check setting-out data

Compute and check setting-out data — Setting Out & Survey Control, step 3

Extract coordinates for grid intersections, foundation corners and centre lines from the design model or drawings. Independently check the coordinate schedule against the drawings — a transposed digit in a spreadsheet is a classic origin of setting-out errors. Upload checked data to the instrument, never hand-key it at the peg.

Step 4: Set out grid lines and building corners

Set out grid lines and building corners — Setting Out & Survey Control, step 4

Set out the primary grid intersections and building corners with the total station, then mark them on profile boards (sight rails) set clear of the excavation lines. Strings stretched between profiles give the trades their working lines without anything standing inside the dig. Pegs inside the excavation area are temporary by definition.

Step 5: Independent check survey

Independent check survey — Setting Out & Survey Control, step 5

A second engineer — or the same engineer from different control — re-measures the critical points. Compare against the design coordinates within the agreed tolerance, typically ±10 mm for foundations and ±5 mm for steel. Nothing is handed to the groundworkers until the check survey passes.

Step 6: Transfer levels to the works

Transfer levels to the works — Setting Out & Survey Control, step 6

Levels are transferred to pegs, rails and the dig itself by level or total station. For deep excavations, level is carried down by tape or EDM to a temporary benchmark at formation. Travellers — staff-like gauges used between the sight rails — give the machine driver a continuous depth check as the dig proceeds. The excavator works to grade indicators or machine control, with the engineer checking formation at a grid of points.

Step 7: Maintain and re-verify control

Maintain and re-verify control — Setting Out & Survey Control, step 7

Re-check primary control monthly and after any event that could disturb it — heavy vibration, frost, a machine strike. Replace disturbed secondary points from primary control immediately, and record every revision. The setting-out drawing is a live document, reissued whenever anything changes.

Step 8: As-built surveys

As-built surveys — Setting Out & Survey Control, step 8

Survey what was actually built: foundation positions and levels, frame geometry, drainage inverts, and final site levels. The as-built records feed the H&S file, the O&M manuals and any future works on the site. On adoption schemes — roads and sewers — the as-builts are a contractual handover requirement.

Plant and equipment

Total station with prisms and tripods
GNSS RTK rover and base station or network subscription
Automatic / laser levels and staffs
Profile boards (sight rails), pegs, nails and spray paint
Machine-control systems on excavators and dozers
Survey software for coordinate geometry and network adjustment

Quality control checks

Closed traverse or loop levelling with misclosure within tolerance
Every set-out point checked from independent control
Check survey by a second person before concrete or steel proceeds
Instrument calibration certificates in date
Control station schedule and protection register maintained
As-built surveys at each hold point, filed with the QA records

Safety considerations

Tripods and staffs clear of machine slew paths and haul routes
Hi-vis and exclusion awareness when working in live excavation areas
Care near excavation edges — pegs are set back, not on the lip
Laser safety for rotating and line lasers

Common defects

Building set out from a single unchecked point — and wrong
Disturbed pegs reinstated by eye instead of from control
Wrong datum: site datum confused with Ordnance Datum, everything 100 mm out
Transposed coordinates from a hand-edited spreadsheet
Grid lines lost at excavation and re-established approximately
As-builts left to the end and nobody remembers what was buried

Best suited for

Every project above garden-wall scale — the framework all tolerances hang from
Tight urban sites where datums must survive months of heavy plant and scaffolding
Transferring control up multi-storey frames and down into basements
As-built verification for QA records, payment and dispute defence
Machine-controlled earthworks and piling where coordinates drive the plant

How long does Setting Out & Survey Control take?

Typical duration: Primary control takes 2–5 days; setting out then continues as an ongoing service through every stage of the build..