Facilitating Services by Chasing and Drilling in Autoclaved Aerated Concrete Structures in the Workplace — Cskills Awards, part of the NOCN Group National Vocational Qualification Construction & Building Services Revision
This subtopic covers the practical skills and underpinning knowledge required to chase and drill openings in autoclaved aerated concrete (AAC) structures f
Topic Synopsis
This subtopic covers the practical skills and underpinning knowledge required to chase and drill openings in autoclaved aerated concrete (AAC) structures for the installation of building services, such as electrical conduits and plumbing pipework. Candidates must demonstrate the ability to interpret contract information, select appropriate tools and materials, and execute the work safely while maintaining structural integrity and minimising damage to the surrounding area.
Key Concepts & Core Principles
- Off-site manufacturing (OSM): Production of building components in a factory-controlled environment, reducing waste and improving quality.
- Structural insulated panels (SIPs): High-performance panels used for walls, roofs, and floors, providing excellent thermal insulation and structural strength.
- Timber frame systems: Prefabricated wooden frames that form the structural skeleton of a building, often combined with cladding and insulation.
- Modular construction: Volumetric units (pods) manufactured off-site and assembled on-site to create complete rooms or buildings.
- Health and safety in MMC: Specific risks include lifting heavy panels, working at height during assembly, and managing site logistics for large components.
Exam Tips & Revision Strategies
- For portfolio evidence, include annotated photographs showing the before, during, and after stages of chasing, with a ruler or tape measure in shot to verify dimensions.
- Produce a short written statement or tool-box talk explaining the specific properties of autoclaved aerated concrete and why dust control measures are critical.
- Cross-reference your risk assessment and method statement directly to the contract drawings and cite relevant legislation (e.g., Control of Substances Hazardous to Health for dust, Work at Height Regulations if using steps).
- If an observation is used, ensure your assessor records a professional discussion where you explain how you would rectify an incorrect chase depth, demonstrating your understanding of the rectification process.
- Highlight any instances where you identified a discrepancy between drawings and actual site conditions and how you communicated this appropriately to the supervisor.
- Always reference relevant legislation by name in your written answers or discussions, such as the Control of Substances Hazardous to Health (COSHH) Regulations 2002.
- For practical assessments, narrate your actions as you work to clearly demonstrate underpinning knowledge to the assessor.
- Ensure you can explain the properties of AAC that influence chasing and drilling, such as its porosity and lower compressive strength compared to dense concrete.
Common Misconceptions & Mistakes to Avoid
- Using traditional hammer and bolster on AAC without scoring first, leading to irregular edges or excessive breakout beyond the required chase width.
- Failing to wear adequate respiratory protection; underestimating the fine dust generated when cutting AAC, which can contain crystalline silica.
- Not checking for embedded services (e.g., electric cables, pipes) before starting, risking service strikes and potential injury.
- Over-chasing deep into the structural web of reinforced AAC panels, compromising load-bearing capacity.
- Poor alignment of drill holes for pipework, causing misalignment of services and requiring corrective re-drilling or packing.
- Ignoring manufacturer guidance on fixing methods or chase dimensions, leading to non-compliance with warranty conditions.
Examiner Marking Points
- Award credit for accurately interpreting drawings, specifications, and schedules to determine the location, size, and depth of chases and drillings for services.
- Assessor must see evidence of selecting correct tools and equipment for AAC, such as specialist chasing tools or dust-extracted cutters, and explaining why they are appropriate.
- Credit for demonstrating safe working practices, including checking for hidden services (e.g., using a cable detector), erecting appropriate access equipment, and wearing task-specific PPE (e.g., respiratory protection for dust).
- Look for evidence of setting out chase lines accurately with minimal deviation and drilling holes plumb and level as per contract information.
- Award credit for minimising damage by protecting adjacent surfaces, using dust extraction, and making good any minor spalling or oversailing with approved repair materials.
- Assessor should confirm that work is completed within an acceptable timeframe without compromising quality, and that waste materials are disposed of correctly.
- Credit for verifying completed chases and drillings against the specification, including dimensions, positions, and falls where applicable, and documenting any variations.
- Award credit for correctly identifying and interpreting all given information, including drawings, specifications, and risk assessments.