Apply basic levelling procedures

CPC Construction, Plumbing and Services Training Package · about a 7-minute read · prints clean as a handout

Why this unit matters

This unit is about using basic levelling equipment — spirit levels, automatic (optical) levels and laser levels — to find, transfer and mark heights on a construction site. Every slab, wall frame, drainage run and finished floor is built off the levels you set, so getting them right, and being able to prove they're right, is a skill every trade relies on.

1Plan and prepare

Get the job requirements first. Pull them from the drawings, specifications and work instructions, and confirm anything unclear with the supervisor, leading hand or other relevant personnel before you plan the task — then build the plan around what they say.
Walk the work area. Look for conditions and hazards within the scope of your role: uneven ground, trenches and penetrations, overhead services, plant and vehicle movement, weather. Report hazards according to workplace procedures — don't just work around them.
Confirm the health and safety requirements that apply — the site safety plan, any SWMS or JSA covering the task, site inductions and the PPE required (hard hat, hi-vis, safety boots, eye protection) — and apply them to your planning, not as an afterthought.
Select tools and equipment to suit the job: spirit level, string line and line level, automatic/optical level with tripod and staff, or laser level with a receiver.
Check everything for serviceability before starting: tripod legs and clamps secure, bubble vials intact, staff sections locking and clean, batteries charged, lenses undamaged. Rectify faults if you can; otherwise tag the item and report it. Never start work with faulty gear.
Confirm team roles and communication signals — the verbal calls and hand signals between the instrument operator and the staff holder — before you begin, especially on a noisy site or when working over distance.

2Set up and use the levelling device

Identify the required heights or levels from the work instructions: the datum or benchmark you're working from, and the reduced levels (RLs) or finished levels you need to establish.
Set the instrument up properly: tripod legs spread and firm, feet pushed in, head roughly level, then level the instrument using its circular bubble and footscrews. Focus the crosshairs to remove parallax before reading.
Check the instrument is within tolerance before trusting it. For an automatic or optical level that means a two-peg test against the manufacturer's stated tolerance — see the walkthrough below.
Shoot the levels: take a backsight to a point of known height, then intermediate sights and foresights to the points you need. Transfer the heights to the required locations and mark them clearly per the job requirements — pegs, profiles, wall datum lines.
Prove your accuracy: set up and read from two instrument positions, and close the run back to your starting datum. If it doesn't close within tolerance, find the error — never fudge it.
Document the results the way your organisation requires: booking sheets (rise-and-fall or height-of-collimation), entries legible, arithmetic checked, dated and identified.

The two-peg test in 60 seconds

The standard field check that your automatic/optical level's line of sight is true.

Press play to walk through the check.

3Clean up

Clear the work area when the task is done: remove pegs, string lines and offcuts no longer needed, and leave the area safe for the next trade.
Sort materials for reuse, recycling or disposal according to statutory and regulatory authority requirements and the site's waste procedures — timber, metals and general waste each go to the right place.
Clean, check and maintain tools and equipment to the manufacturer's specifications: wipe down the staff, dry the instrument before casing it, clean lenses only with a lens brush or cloth — never bare fingers.
Store everything correctly — instrument secured in its case, tripod strapped, staff collapsed and clipped — and report any damage you find so it's fixed before the next use.

Knowledge evidence, distilled

Know this cold

Levelling devices — what each is for and where it lets you down

Device	Best for	Limits — watch for
Spirit level	Level and plumb over its own length — frames, posts, short runs	Only as accurate as its vials; check it by flipping end-for-end
String line + line level	Approximate level between two points over a short span	Line sag distorts readings over long spans; wind moves the line
Water level (clear hose)	Transferring equal heights around corners and obstructions	Air bubbles or kinks in the hose give false readings
Automatic / optical level + staff	Accurate levelling over distance; many points from one setup	Needs a two-peg check; staff must be plumb; usually two people
Laser level + receiver	One-person levelling; a continuous level plane across the site	Battery and calibration checks; never look into the beam or sight it through an optical instrument

The calculations

HoC = known RL + backsight

new point RL = HoC − staff reading

check every page: ΣBS − ΣFS = last RL − first RL

If the page doesn't balance, there's a booking or arithmetic error — find it before you trust a single mark.

Two booking methods: rise-and-fall (compare each reading with the previous one) and height of collimation (work everything from the instrument height). Know at least one thoroughly, including its check.
Setting out a levelling task: start from a site datum or benchmark, establish temporary benchmarks (TBMs) where useful, work through the points in a logical sequence, and always close the run.
Line, level and plumb: line = straight in alignment, level = truly horizontal, plumb = truly vertical. Structures depend on getting all three right.
Plan symbols and terminology: RL (reduced level), FFL (finished floor level), NGL (natural ground level), datum marks, contour lines, section marks and scales — you must be able to pull the required heights straight off the drawings.
Technique essentials: read the staff in metres to three decimal places (estimate the final millimetres), keep backsight and foresight distances roughly balanced, and keep the staff plumb — use its bubble, or rock it gently and take the lowest reading.
JSA and SWMS: both break a task into steps, hazards, risk controls and responsible persons. Under the WHS Regulations a SWMS is mandatory for high-risk construction work. Read the one covering your task before you pick up the gear, and work to it.
Site and equipment safety for levelling: exclusion zones around plant and traffic, tripods and string lines as trip hazards, laser classes and eye safety, sun and weather protection, and secure two-handed carrying of instruments.

Common mistakes

Where people slip up

1“The bubble's centred, so the level's right.”

The bubble only tells you the instrument body is level — not that its line of sight is true. Fix: run a two-peg test before precise work and again after any knock or drop.

2Staff not plumb

A leaning staff always reads high, and the error grows with the reading. Fix: use the staff bubble, or rock the staff slowly toward and away from the instrument and book the lowest reading.

3Booking errors nobody checks

Backsights booked as foresights, transposed digits, sloppy handwriting. Fix: book neatly as you go and run the arithmetic check (ΣBS − ΣFS) on every page before you leave the setup.

4Never closing the run

If you don't level back to your datum, an error can hide in every mark you've made. Fix: close every run and compare the misclose against the allowable tolerance — outside tolerance means re-do, not round off.

5Packing up wet and dirty

Moisture fogs optics and corrodes fittings; grit scratches lenses. Fix: dry and clean the instrument and staff before casing them, per the manufacturer's specs, and report damage instead of hiding it.

Key terms

Mini-glossary

Datum: The reference height (RL) that all other levels on the job are measured from.
Benchmark / TBM: A permanent (benchmark) or temporary (TBM) marked point of known height used to start and check level runs.
Reduced level (RL): The height of a point relative to the datum.
Backsight (BS): The first reading from a setup, taken onto a point of known height.
Foresight (FS): The last reading from a setup, onto the point you're transferring height to.
Intermediate sight (IS): Any reading taken between the backsight and the foresight.
Height of collimation (HoC): The RL of the instrument's line of sight: HoC = known RL + backsight.
Two-peg test: The standard field check that an automatic/optical level's line of sight is true within the manufacturer's tolerance.
Staff: The graduated telescopic rod (metric, read to millimetres) held vertically on the point being levelled.
Line, level and plumb: Straight in alignment, truly horizontal, and truly vertical — the three checks construction work is judged against.
Parallax: Apparent movement of the crosshairs against the target when the eyepiece isn't focused — remove it before reading.
FFL: Finished floor level, as shown on the drawings.
SWMS / JSA: Safe work method statement (mandatory for high-risk construction work) and job safety analysis — both set out task steps, hazards and controls.
Tolerance: The allowable error stated by the manufacturer or the specification. Outside tolerance = stop and fix before proceeding.
Misclose: The difference between where a level run finishes and the known value it should finish on.