Building Skills
Site Surveys and Set-Out Procedures
The complete guide to site surveying and building set-out for Australian construction. Learn levelling techniques, contour plans, cut and fill calculations, and the accuracy standards that ensure your buildings are positioned correctly from day one.
3mm
Set-Out Tolerance/10m
1mm
Level Error/10m Max
1:100
Min Drainage Fall
2cm
RTK GPS Accuracy
The Fundamentals
What Are Site Surveys and Set-Out Procedures?
Site surveys and set-out procedures are the technical methods used to accurately position a building on its site. This involves three key activities:
- Site surveying — Measuring and recording existing ground levels, contours, and features
- Set-out — Transferring design dimensions from plans to physical markers on the ground
- Levelling — Establishing and verifying heights relative to a datum (reference point)
These skills ensure buildings are constructed in the correct position, at the correct level, and to the correct dimensions as specified in approved plans.
Why Accuracy Matters
- Buildings must meet boundary setbacks per development approval
- Incorrect levels compromise foundations and drainage
- Errors discovered late cost significantly more to fix
- Other trades rely on accurate set-out for their work
- Tolerances exist for professional workmanship compliance
Competency Standards
In Australia, site surveying and set-out is covered by national competency units:
- CPCCBC4018 — Apply site surveys and set-out procedures
- CPCCCA3002 — Carry out setting out
These units are part of the Certificate IV in Building and Construction and the Diploma of Building and Construction — key steps towards obtaining your builder's licence.
Tools of the Trade
Essential Surveying Equipment
Different instruments suit different applications. Here's what you need to know about the equipment used for site levelling and set-out in construction.
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Optical (Dumpy) Level
The most common instrument for construction levelling. Provides a horizontal line of sight when properly set up.
- Requires staff and assistant
- Must check with two peg test
- Accuracy: <1mm per 10m
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Laser Level
Projects visible laser beam for quick reference. Rotating models create 360-degree horizontal plane.
- Self-levelling models available
- Faster setup than optical
- Accuracy: 1-6mm per 20m
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Water Level (Tube Level)
Simple, low-cost option based on Pascal's Law — water finds its own level in a connected tube.
- Works around obstacles
- Min 1/2 inch tube diameter
- Watch for air bubbles
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Total Station
Combines theodolite, EDM, and computer. Measures angles and distances simultaneously with high precision.
- Up to 1,500m range with prism
- 0.5 arc-second accuracy possible
- Essential for precise commercial work
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Equipment Check Frequency
Optical levels should be checked with a two peg test at least weekly or before any critical works. Laser levels should be calibrated according to manufacturer specifications — typically annually by an authorised service centre.
Quality Control
How to Perform the Two Peg Test
The two peg test checks for collimation error in an optical level — the angular offset that causes readings to deviate from true horizontal. It's essential quality control before any levelling work.
Collimation Error =
[(S1 - S2) - (S3 - S4)] ÷ Distance Between Pegs⚠️
Acceptable Tolerance
The collimation error must be less than 1mm per 10m of sighted distance(or ±1mm per 20m). If the error exceeds this, the instrument needs adjustment by a qualified technician before use.
Height Reference
Understanding Reduced Levels (RLs)
A Reduced Level (RL) is the height of a point recorded relative to a specific reference datum. Understanding RLs is fundamental to all construction levelling work.
Australian Height Datum (AHD)
The national reference system for height measurements in Australia, based on mean sea level observations from 30 tide gauges (1966-1968).
- Required for council approvals
- Determines minimum floor levels
- Only Licensed Surveyors can perform official AHD surveys
Arbitrary Datum
A local reference point chosen for convenience on site. Often assigned a round number (e.g., 100.000m) to avoid negative values.
- Used when AHD not required
- Simpler for internal site work
- Must be stable and clearly marked
Key Terminology
- BM (Benchmark) — A permanent reference marker, often on the kerb or survey peg
- TBM (Temporary Benchmark) — Reference point established for construction duration
- FFL (Finished Floor Level) — Expected floor height relative to datum
- NGL (Natural Ground Level) — Existing ground level before any earthworks
Note: According to AS 1100.301, levels should be expressed in metres to three decimal places (nearest 5mm) on construction drawings.
Calculation Methods
Rise & Fall vs Height of Collimation
Two methods exist for recording and reducing level readings. Each has strengths and limitations — choosing the right method depends on your project requirements.
Height of Collimation (HPC)
FasterCalculates the height of the instrument's line of sight, then subtracts each staff reading to find RL.
RL = HC – Staff Reading
Best For:
- Long runs with few change points
- Construction profile levelling
- When speed matters
Limitations:
- No check on intermediate readings
- Errors not detected until end
Rise and Fall
More AccurateCalculates the difference between consecutive readings to determine rises or falls, then adjusts from previous RL.
RL = Previous RL ± Rise/Fall
Best For:
- Complex or critical work
- Check levelling
- Runs with many change points
Advantages:
- Continuous error checking
- Three accuracy checks vs two
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Which Method to Choose?
Use Height of Collimation for routine construction work where speed matters and you have few intermediate sights. Use Rise and Fall when accuracy is critical, you need to verify work, or you have many change points in your run.
Step by Step
Building Set-Out Procedure
Setting out transfers design dimensions from plans to physical markers on site. Follow this procedure to achieve the required 3mm tolerance over 10 metres.
01
Site Preparation
Clear and strip topsoil and vegetation to 100-300mm depth depending on footing design. Ensure the site is accessible for equipment.
02
Locate Survey Pegs
Find and identify boundary pegs from the survey plan. Verify their positions match the site plan before proceeding.
03
Install Profile Boards
Set up hurdles (profile boards) approximately level, positioned minimum 2 metres back from the building line to allow excavator access.
04
Mark Building Lines
Attach string lines to profile boards marking the outside perimeter of construction and critical measurements.
05
Check for Square
Verify corners are at 90° using the 3-4-5 method or by checking diagonals are equal. Adjust string lines as needed.
06
Transfer Levels
Establish a TBM on site and transfer design levels to profile boards — floor level, footing depths, and other critical heights.
Essential Technique
The 3-4-5 Method for Right Angles
The 3-4-5 method is a simple, reliable technique for establishing and checking 90-degree angles on site. It's based on the Pythagorean theorem (3² + 4² = 5²) and requires only a measuring tape.
Alternative: Diagonal Check
For rectangular buildings, you can also check corners by measuring both diagonals. If the diagonals are equal, the corners are square. This method is often used in conjunction with the 3-4-5 method for verification.
Site Analysis
Understanding and Creating Contour Plans
Contour plans show the lay of the land by connecting areas of equal height. They're essential for determining earthworks, drainage design, and building platform levels.
Contours Help Determine
- Cut and fill requirements
- Retaining wall heights
- Drainage gradients
- Building platform levels
- Split-level vs slab-on-ground suitability
Modern Methods
Today, contour surveys are often performed using:
- RTK GNSS (1-2cm accuracy)
- Drone photogrammetry
- LiDAR scanning
- Total station surveys
Earthworks
Cut and Fill Volume Calculations
Cut and fill is the earth-moving technique used to create a level building platform. Cut removes earth from higher ground; fill adds earth to lower areas. The goal is to balance these operations to minimise costs.
Average End Area
Simplest method — averages two cross-section areas.
V = (A₁ + A₂) / 2 × L
Where A = area, L = distance between sections
Prismoidal Method
More accurate — accounts for middle cross-section.
V = L(A₁ + 4Am + A₂) / 6
Where Am = area at midpoint
Pyramid Method
Used when one end area equals zero.
V = A × L / 3
Common at site boundaries
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Account for Swell and Shrinkage
Swell factor: Excavated material expands (typically 20-40% for clay soils). You'll need more trucks than the in-situ volume suggests.
Shrinkage factor: Fill material compacts when placed and rolled (typically 10-15%). You'll need more material than the void volume.
Volume calculations like these are covered in depth in the Certificate IV in Building Project Support (Estimator), where you'll learn to apply them to real project costing and earthworks estimation.
Water Management
Grades, Falls, and Drainage Calculations
Correct grades ensure water flows away from buildings and through drainage systems. Understanding gradient calculations is essential for site works and pipe installation.
Minimum Grade Requirements
| Application | Minimum Grade | Standard/Source |
|---|---|---|
| Stormwater pipes (<150mm) | 1:100 (1% or 10mm/m) | AS/NZS 3500 |
| Surface drainage | 1:100 minimum | General practice |
| Paved areas | 1:80 to 1:100 | General practice |
| Driveways | 1:20 maximum (5%) | AS 2890.1 |
Grade Calculation Formulas
- As decimal: Rise ÷ Run (e.g., 0.5 ÷ 10 = 0.05)
- As percentage: (Rise ÷ Run) × 100 (e.g., 0.05 × 100 = 5%)
- As ratio: 1:X where X = Run ÷ Rise (e.g., 1:20)
- In degrees: arctan(Rise ÷ Run)
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Batter Slope Ratios by Soil Type
0.75:1 — Hard, solid soil (steeper)
1:1 — Soil likely to crack or crumble
1.5:1 — Soft, sandy, loose soil (gentler)
Always consult geotechnical advice for permanent excavations or retaining structures.
Quality Control
Common Surveying Errors and How to Avoid Them
Surveying errors fall into three categories. Understanding them helps you implement proper checking procedures and achieve required tolerances.
Error Types and Prevention
| Error Type | Examples | Prevention |
|---|---|---|
| Gross Errors (Mistakes) | Misreading tape, booking wrong number, sighting wrong target | Independent check measurements, careful recording, clear communication between surveyor and staff holder |
| Systematic Errors | Collimation error, tape not calibrated, temperature expansion, incorrect datum | Two peg test, calibrated equipment, apply corrections for temperature, verify benchmarks |
| Random Errors | Human judgement variations in reading scales, atmospheric refraction, slight levelling errors | Multiple readings and average, consistent technique, favourable conditions, closed loops |
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Accuracy vs Precision
Accuracy = How close to the true value (correctness)
Precision = How close repeated measurements are to each other (consistency)
High precision doesn't guarantee accuracy — systematic errors can cause consistent but wrong results. Always check against known points.
Common Questions
Frequently Asked Questions
Basic site levelling requires an optical (dumpy) level or laser level, a levelling staff, measuring tape, and a tripod. For more precise work, you may need a total station or theodolite. Water levels are a simple, low-cost option for checking levels around obstacles. The choice depends on your project's accuracy requirements and budget.
Disclaimer: This information is general in nature and intended as an educational overview. Site surveying for legal purposes (boundaries, subdivisions) must be performed by a Licensed Surveyor. Tolerances and requirements may vary by state, territory, and project type. Always verify current requirements with your local council and refer to approved plans and specifications for your specific project.
Develop your site surveying skills with our Certificate IV in Building and Construction or Diploma of Building and Construction. Study while you work with our flexible online delivery.
SITE SURVEYS & SET-OUT
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