How to excavate for strip footings
This guide details the precise excavation process for strip footings, a fundamental component of structural foundations for residential and light commercial buildings. Proper excavation ensures compliance with engineering specifications and Australian Standards, providing a stable base for the concr
- Skill level
- Intermediate
- Time
- 1-2 days (depending on footing length and ground conditions)
- Trade
- Building & Construction
- Updated
- 4 November 2026
Tools you will need
- Excavator/Trencher: Mini excavator
- String Line & Pegs: For accurate set
- Measuring Tape: 8m or 10m steel tape.
- Spirit Level: 1200mm or 1800mm box level.
- Laser Level: Self
- Wheelbarrow: Heavy
🧱 Excavating for Strip Footings
What is involved in excavating for strip footings?
This guide details the precise excavation process for strip footings, a fundamental component of structural foundations for residential and light commercial buildings. Proper excavation ensures compliance with engineering specifications and Australian Standards, providing a stable base for the concrete pour.
What skill level is required for excavating strip footings?
Intermediate — Estimated time: 1-2 days (depending on footing length and ground conditions)
What tools are essential for excavating strip footings?
Excavator/Trencher: Mini excavator (1.5-3 tonne) with a 300mm or 450mm trenching bucket, or a dedicated walk-behind trencher for smaller projects. String Line & Pegs: For accurate set-out and depth control. Measuring Tape: 8m or 10m steel tape. Spirit Level: 1200mm or 1800mm box level. Laser Level: Self-levelling rotary laser with receiver and staff. Shovel & Pick: Square mouth and pointed shovel, mattock/pick for fine-tuning and hard ground. Wheelbarrow: Heavy-duty for spoil removal. Compactor/Jumping Jack: For compacting the trench base if required by engineer. Batter Boards: Timber or steel for establishing accurate string lines.What materials are needed for strip footing excavation?
Survey Pegs: Timber or steel. String Line: High-visibility, non-stretch. Spray Paint: For marking out. Formwork Timber: 90x45mm or 100x50mm for batter boards.What are the critical safety requirements for strip footing excavation?
⚠️ PPE: Hard hat, high-visibility clothing, safety glasses, steel-capped boots, hearing protection (when operating machinery), gloves. ⚠️ Excavation Safety: Trench Stability: Trenches deeper than 1.5m require shoring or battering back. For strip footings, depths are typically less, but always assess ground stability. Underground Services: Always obtain Dial Before You Dig (DBYD) plans and physically locate all underground services (electrical, gas, water, sewer, comms) before commencing excavation. Hand dig within 500mm of marked services. Spoil Piles: Keep spoil piles at least 600mm from the edge of the trench to prevent collapse. Access/Egress: Ensure safe means of entry and exit from trenches. Machinery Operation: Only operate machinery if licenced and competent. Maintain a safe distance from operating machinery. Manual Handling: Use correct lifting techniques for tools and materials.Step-by-Step Guide
Step 1: 1️⃣ Site Preparation & Set-Out
Clear the footing line of any debris, vegetation, or topsoil. Establish the building's corners and perimeter using survey pegs and string lines, referencing the architectural and structural plans. Use batter boards set back from the proposed footing line to maintain the string line reference points during excavation. Mark the exact width of the footing on the ground with spray paint, typically 300mm to 450mm wide as per engineering specifications.
Step 2: 2️⃣ Establish Datum & Depth Control
Set up a laser level to establish a consistent datum point across the entire footing area. This datum will be used to accurately control the excavation depth. The structural plans will specify the required depth from finished ground level or a specific reduced level. Use the laser receiver on the excavator bucket or a staff to ensure the trench bottom is excavated to the correct, consistent depth.
Step 3: 3️⃣ Initial Trench Excavation
Using the excavator or trencher, begin excavating the trench. Start by cutting to the approximate depth, following the marked lines. For excavators, maintain a consistent bucket width. For trenchers, ensure the machine is guided straight along the marked line. Work systematically, removing spoil to a designated area, ensuring it's clear of the trench edge.
Step 4: 4️⃣ Achieve Final Depth & Level
Once the bulk of the excavation is complete, use the laser level and staff to fine-tune the trench bottom. The base of the footing must be level and at the exact depth specified by the engineer. Use a shovel and pick for precise trimming. Any over-excavation must be backfilled with lean concrete or approved compacted fill, as specified by the engineer. Refer to AS 2870 Residential Slabs and Footings for general guidance, but always adhere to specific engineering designs.
Step 5: 5️⃣ Trench Base Preparation
Inspect the trench base for any loose material, soft spots, or organic matter. Remove any such material. If specified by the engineer, compact the trench base using a compactor or jumping jack to achieve the required bearing capacity. The base must be firm and stable. Ensure the trench walls are as vertical as possible to minimise concrete volume and provide a clean form.
Step 6: 6️⃣ Final Inspection & Engineering Sign-Off
Before any steel reinforcement is placed or concrete is poured, conduct a thorough final inspection of the excavated trenches. Check all dimensions (width, depth, length), levels, and the condition of the trench base. Ensure compliance with the structural drawings. In most cases, a structural engineer will need to inspect and approve the footing excavation prior to concrete placement.
Common Mistakes to Avoid
Pro Tips
💡 Weather Watch: Plan excavation around dry weather. Rain can quickly turn a well-prepared trench into a muddy mess, requiring re-work. 💡 Spoil Reuse: If the excavated material is suitable, plan for its reuse on-site (e.g., backfilling around the slab) to save on disposal and import costs. 💡 Laser Level Proficiency: Invest time in becoming highly proficient with a laser level. It's your most valuable tool for accuracy and efficiency. 💡 Bucket Selection: Use the correct bucket width for the specified footing width. A 300mm bucket for a 300mm footing minimises hand trimming. 💡 Engineer Consultation: If unsure about ground conditions or specific requirements, always consult with the structural engineer before proceeding.Recommended Tools
🔧 Topcon RL-H5A Laser Level: Renowned for accuracy, durability, and ease of use on construction sites. 🔧 Hitachi ZX17U-5A Mini Excavator: A versatile and reliable 1.7-tonne excavator, ideal for residential footing excavation. 🔧 Stabila Type 196-2 Spirit Level: A high-quality, robust spirit level for precise checking of trench bases. 🔧 Husqvarna LF 75 L Plate Compactor: A powerful and efficient compactor for achieving required base density.Frequently asked questions
- What is involved in excavate for strip footings?
- This guide details the precise excavation process for strip footings, a fundamental component of structural foundations for residential and light commercial buildings. Proper excavation ensures compliance with engineering specifications and Australian Standards, providing a stable base for the concr
- What skill level do I need for excavate for strip footings?
- Intermediate — Estimated time: 1-2 days (depending on footing length and ground conditions)
- What are common mistakes when excavate for strip footings?
- 1. Inaccurate Set-Out: Incorrectly marking the footing lines leads to misaligned foundations and potential structural issues. 2. Over-Excavation: Digging too deep requires costly backfilling with lean concrete or engineered fill, adding time and expense. 3. Ignoring Underground Services: Failing to locate services can result in dangerous and expensive damage. 4. Uneven Trench Bas
- What tools do I need for excavate for strip footings?
- This guide includes a comprehensive tools list. Key building & construction tools are detailed in the Tools Required section.
- What is the Australian standard for residential footings?
- The primary Australian standard for residential footings is AS 2870-2011 'Residential slabs and footings'. This standard outlines requirements for the design and construction of concrete slabs and footings, considering soil conditions and structural loads. Always consult a structural engineer for site-specific designs.
- How deep should strip footings be in Australia?
- The required depth for strip footings in Australia varies based on soil conditions, frost heave potential, and engineering specifications. Generally, footings should extend into stable, undisturbed soil, typically a minimum of 450mm below natural ground level, as per common engineering practice and AS 2870-2011 guidelines.
- What is the 'Dial Before You Dig' service?
- Dial Before You Dig (DBYD) is a free national referral service in Australia that helps prevent damage and disruption to underground infrastructure. By submitting an enquiry, you receive plans from member organisations detailing the location of their underground assets, such as electricity cables, gas pipelines, and communication lines, before any excavation commences.
- What PPE is mandatory for excavation work in Australia?
- Mandatory Personal Protective Equipment (PPE) for excavation work in Australia, as advised by SafeWork Australia, includes a hard hat, high-visibility clothing, safety glasses, steel-capped boots, hearing protection (when operating machinery), and gloves. Additional PPE may be required based on specific site hazards and risk assessments.
Written by Bricko, the Building & Construction specialist at Aus.Tools.