At Keswick Electrical Services Ltd, we know that pulling cables through floors and ceilings might not sound glamorous, but it’s the backbone (or should we say floorbone?) of any good electrical installation.
Drilling Holes in Joists
One of the most common – and most crucial – tasks we carry out is drilling holes in joists to run cables safely and efficiently.
It may sound simple, but getting it wrong can have serious consequences. Let’s dig into why it’s so important to drill joists properly, how to do it safely, and how using a professional team like Keswick Electrical Services keeps your property compliant and structurally sound.
Why You Can’t Just Drill Anywhere
Joists are the horizontal supports that hold up your floors and ceilings. They're vital to the structure of your home or business, and compromising them can lead to big problems – from bouncy floors to serious safety risks. Drill a hole in the wrong place, and you might weaken the joist to the point where it can no longer bear weight properly. Over time, that can lead to sagging, cracks in the ceiling below, or worse – structural failure.
The UK Regulations: What the Rules Say
When it comes to notching and drilling joists, the UK Building Regulations and BS 7671 (IET Wiring Regulations) are crystal clear. Here are the key rules electricians must follow:
Drilling Holes in Joists:
- Location - Holes must only be drilled along the centre line (neutral axis) of the joist – that’s the middle vertically, where the stress is lowest.
- Distance from Supports - Holes must be no closer than 0.25x the span length from either end of the joist, and no further than 0.4x the span.
- Hole Size - The hole diameter must not exceed 0.25x the depth of the joist.
- Spacing - Leave at least three diameters between multiple holes.
Notching Joists:
- Location - Notches can only be made in the top of the joist, within the first 0.25x of the span from the end.
- Notch Size - Notches must be no deeper than 0.125x the joist depth.
So if you've got a 200mm deep joist spanning 4m:
- Holes can be drilled between 1m and 1.6m from the end.
- The maximum hole diameter is 50mm.
- Notches can only be made in the top, within 1m of the end, and no deeper than 25mm.
Tips for Drilling Joists the Right Way
If you’re keen to understand what goes into safe drilling, here are a few professional tips from the Keswick Electrical team:
- Measure Twice, Drill Once – Take accurate measurements of both the joist span and depth before drilling.
- Use a Stud Finder or Joist Scanner – To ensure you’re not drilling near pipes, nails, or previous damage.
- Avoid Overloading – Never drill too many holes close together. Stick to spacing regulations to keep the structure strong.
- Go Slow and Straight – Use a sharp bit and keep the drill level to avoid splintering or angled holes.
- Mark Your Entry and Exit – It’s easy to drift off-target if you’re not paying attention.
Why It Pays to Use a Professional
Drilling holes in joists might seem like a small task, but the consequences of doing it incorrectly can be costly – and dangerous. That’s why it's always worth trusting a qualified electrician who understands the latest UK regulations and respects the integrity of your building.
At Keswick Electrical Services Ltd, we’ve been keeping properties across London & Kent safe and sound with expert electrical installations done to the highest standard. Whether you’re rewiring a home, renovating a commercial space, or just running a few new circuits, we make sure your cables are routed smartly – and your joists stay strong.
Ready for a Safe, Compliant Installation?
If you’re planning electrical work and want the peace of mind that comes with using a professional, friendly, and fully qualified team – Keswick Electrical Services Ltd is here to help. We’ll keep your project on track, your property structurally sound, and everything fully compliant with UK regulations.
Get in touch today to book a consultation or learn more about our services.
