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Modern LGS frames are supplied with pre-punched holes in appropriate locations and sufficient quantity to cover the majority of requirements for electrical and plumbing routing. Typically service holes are provided in each top plate, noggin and stud. Common service holes range from 28-34 mm diameter and these are generally aligned between adjacent frame members.
Depending on the frame design, the pre-punched service holes may be punched and flared, (no need for cable grommets unless less than 90 degrees), or if not flared, site installed grommets as shown below should be placed in the holes. If additional holes are made on site then these will require grommets to provide cable protection.
Service hole diameter and spacing, whether factory-applied or made on-site, is required to meet NASH residential and low-rise steel framing design standards. For further information refer to separate topic on this site relating to Service Holes.
A range of grommet types and sizes are commercially available. Grommets have tabs or ribs to positive lock into the frame to ensure they stay in place when routing cables.
Where congestion occurs such as in wet areas and kitchens, or where specific routing is required, additional site cut service holes may be needed.
Mechanical hole punches are the most efficient tool for adding service holes on-site if required. The tools have interchangeable die sets which are quick to change over to adjust the hole diameter. These tools tend to be durable with long tool life. The tool produces a clean hole and single-disc waste in the punching process.
Another option for punching additional holes is to use a drill driver with accessories such as metal hole saws and step drill bits.
These are a fast way to place additional holes in difficult areas where punches are unable to reach.
- LGS frames are delivered to the site with pre-punched service holes for follow-on trades to complete efficient installation. They aim to make it easier for the electrician to comply with AS/NZS 3000 requirements.
- Service holes that are not flared in the factory, or are punched on-site, require grommets to be inserted to protect electrical cables from mechanical damage.
- There is a small number of prohibited cable locations, e.g. within steel roof frame members or ceiling battens to prohibit fastener cable damage. Otherwise, cable runs are basically the same for timber, steel and masonry structures.
- Follow NASH guidelines when adding holes to LGS frames on site.
- Refer to guidance by NECA and NASH in Electrical Trade Tips documents
- Engage with your local frame supplier(s) to keep them advised of your needs.
Resources
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This guide contains information to help you meet your obligation to comply with AS/NZS 3000 when working on steel framing buildings
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Standards Australia website - Wiring Rules: AS/NZS 3000:2018, Electrical installations, known as the Wiring Rules, are the technical rules that help electricians design, construct and verify electrical installations.
Featured Topic
Service Holes
In this topic, we look at tips to place service holes in steel framing.