Sizing and Fixing CCTV Cable Trunking Properly
Get the trunking cross-section wrong and you'll spend every callback fighting a lid that won't shut or cable clips snapping under load. Match the trunking size to your actual cable count, back it up with the right cable ties, and choose external-grade over indoor-grade where a run goes outside.
That's the difference between a scrappy cable run and one that still looks sharp in five years. This guide walks UK CCTV installers through sizing, fixing and finishing trunked runs, brand-neutral and street-level practical throughout.
For most single-cable CCTV runs — one Cat6 to a camera, say — 16x16mm mini trunking has enough cross-section without looking bulky on a wall. Once you're running two or three cables together, step up to 25x16mm trunking, sold here in 1 metre white PVC lengths with a snap-on lid. Fill the channel much beyond about two-thirds full and the lid stops seating properly, which is usually the actual cause of "trunking won't close" callbacks.
Where a run carries a small loom — three or four cables, or a mix of Cat6 and coax — 40x25mm trunking gives more headroom and still takes a self-adhesive back, though on brick or render we'd still back the adhesive with screw-fixings for anything running externally.
CCTV Cable Trunking, Clips & Tidy Runs: A Fitting Guide (UK 2026)
Size the trunking to how many cables it carries, then match the grade to indoor or outdoor exposure. Get those two decisions right and the run stays neat for years. The single biggest fitting mistake is under-sizing trunking for future cables, so always leave room for at least one spare CAT6 or coax run.
Sizing trunking to cable count for CCTV runs
Match trunking size to cable count: one cable needs 16×16mm, two or three need 25×16mm, four-plus needs 40×25mm. For a single camera drop — one Cat6 cable, maybe a power lead alongside it — 16×16mm mini trunking is enough; the Self-Adhesive Mini Trunking 16x16mm White PVC suits this.
Where a run carries two or three cables — a camera feed plus a spare, or a PoE run alongside a mains spur — step up to 25×16mm. The Self-Adhesive Cable Trunking 25×16mm White 1m with its snap-on lid gives enough cross-section without looking bulky on a wall.
For risers or a hub point feeding four-plus cameras, 40×25mm trunking copes with the extra bulk and any future additions. The 40x25mm Self-Adhesive Cable Trunking White PVC is the size we specify for those multi-camera hub points.
Which trunking size fits your CCTV cable run: 16×16mm, 25×16mm or 40×25mm?
Size trunking to the cables it has to hold, plus enough spare room to snap the lid shut without forcing it. Trunking that's too tight strains the lid clips over time and can pinch coax or Cat6 at bends. Trunking that's oversized just wastes wall depth and looks clumsy, so count your runs first, then pick the channel.
One camera, one run: a single Cat6 or coax cable sits comfortably in 16×16mm mini trunking. The Self-Adhesive Mini Trunking 16x16mm White PVC is sized for exactly that single-cable job, with room for the lid to click home.
Two to three runs: a wall feeding cameras at both ends, or a Cat6 run alongside a separate power feed, needs the extra cross-section of 25×16mm. The Self-Adhesive Cable Trunking 25×16mm White 1m is built for that job. It has enough internal volume for two or three cables side by side without them bowing the lid.
Four or more runs, or a trunk that will pick up extra cameras later: step up to 40×25mm. The 40x25mm Self-Adhesive Cable Trunking White PVC gives real spare capacity for a multi-camera spur. That means you're not stripping the wall and refitting larger trunking in a year.
Quick sizing guide
| Run | Cables | Trunking |
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Mini trunking or external-grade trunking — which do you need?
Self-adhesive mini trunking suits dry indoor runs; solid-wall, screw-fixed trunking is for anywhere exposed to weather, UV, vibration or knocks. The deciding factor is environment, not budget. A strip that looks tidy in an office ceiling void will often fail outdoors within a season.
Indoor runs suit self-adhesive mini trunking well — think server rooms, office ceiling voids, or a hallway run to the NVR. The Self-Adhesive Cable Trunking 25×16mm White 1m is a 1 metre length with a snap-on lid and needs no drilling on a sound painted or plasterboard wall. For lighter camera or network cable runs, the Self-Adhesive Mini Trunking 16x16mm White PVC at 16×16mm tucks into corners neatly without needing paint over it. Where you're bundling several cables together, the 40x25mm Self-Adhesive Cable Trunking White PVC gives more cross-section — 40×25mm against 25×16mm — without stepping up to a rigid duct.
Plant rooms, garages, industrial units and anywhere with vibration or knocks need a rigid, screw-fixed duct rather than an adhesive strip. The Betaduct 37.5×37.5mm PVC Solid Wall Cable Trunking Black
How do you fit trunking round corners and through walls without kinking the cable?
Use the trunking's own moulded corner pieces instead of folding the body, and always sleeve or gland the cable wherever it passes through a wall. Freehand bends crush the channel and put unwanted stress on the cable inside it.
Internal and external corners for cable trunking
Cut mini-trunking on a 45° mitre with a sharp blade rather than bending it. Most mini-trunking, including the self-adhesive 16×16mm and 25×16mm white PVC sections, is designed this way.
Two lengths butted at a clean 45° cut form a neat corner. A proper internal or external corner accessory does the same job without a visible joint, and it avoids the crushed, gaping gap that a freehand cut usually leaves.
Where a run needs to step up in cross-section — say from 25×16mm to something bulkier like the 40×25mm trunking — a reducer coupler keeps the transition tidy. That's a better fix than forcing cables through a narrowed, hand-cut gap.
Flat bends round door frames or up a soffit
For a gentle curve rather than a sharp corner, let the trunking base run long and score it partway through — on the base, never the lid — so it flexes smoothly around the profile.
The cable's own minimum bend radius should always stay wider than the trunking's bend. The trunking can be scored and flexed, but the copper or fibre inside it cannot recover from a tight kink.
What actually causes trunking to sag, gaping or letting water in?
Trunking sag, gaping lids and water ingress almost always trace back to fixing points, not the material. Too few fixings, unsupported spans, or relying on adhesive where a mechanical fixing was needed are the usual culprits.
Sagging cable trunking
Self-adhesive backing on a run like the Self-Adhesive Cable Trunking 25×16mm White 1m holds well over short horizontal spans. On runs longer than roughly a metre without an intermediate fixing point, the base will generally start to bow under the cable's own weight over time.
This is worse overhead or on ceiling runs, where gravity works against the adhesive continuously rather than just at installation. The fix: add a screwed clip or an extra trunking base fixing at regular intervals rather than trusting adhesive alone to carry the load indefinitely.
Gaping lids
A gap between lid and base almost always comes from one of two causes: the trunking is overfilled beyond what its cross-section can comfortably close over, or the lid was cut too short at a joint. Cutting short leaves a permanent gap that no amount of pressing will close.
When cutting lids to length, leave a fraction extra and trim back afterwards. Stepping up from a 16x16mm mini trunking to something like the 40x25mm Self-Adhesive Cable Trunking White PVC gives more working room before overfilling becomes an issue.
Water ingress on exposed cable runs
On external or semi-exposed runs, water more often tracks in through open trunking ends, unsealed corner joints and wall penetrations than through the trunking body itself.
Recommended kit
For the setup above, this is the kit we'd fit from our own range:
This article was researched and written by IT Master.
