Conduit Clips: Sizes, Spacing, and How to Fix Conduit Properly
Plastic conduit clips and saddles secure oval and round conduit before plastering. Sizes, 300mm spacing rule, quantities, and prices from £1.10 a pack.
The electrician chases a line up the wall, drops the oval conduit in, and blobs a touch of bonding over it to hold it while he moves on. The plasterer comes along, presses his trowel against the wall, and the conduit kicks sideways. Now there is a buried tube wandering off line, the cable inside is harder to pull, and nobody knows where it runs. A 22p clip every 300mm would have stopped that. Conduit clips are the cheapest item on the first-fix list and the easiest to skip.
What conduit clips are and what they do
Conduit clips, also called conduit saddles or oval conduit clips, are small plastic (occasionally metal) fixings that hold electrical conduit firmly against a wall or inside a wall chase. Conduit itself is the protective tube that cables run through. Oval conduit is the flattened PVC tube chased into masonry walls so the channel can be shallow; round conduit is the rigid tube used for surface-mounted runs along a wall or ceiling. The clips are what keep that tube where the electrician put it.
They matter for two reasons. During first fix, the conduit has to stay dead straight and dead still while the plasterer works over it, because once it's buried you can't adjust it. After the build, the clips keep surface-mounted conduit from sagging or pulling away, which protects the cable inside from strain. A run of conduit with no clips is just a loose tube waiting to move.
There's no single British Standard for the clip itself, but the spacing rules come from the wiring regulations. BS 7671 (the IET Wiring Regulations, the rulebook every UK electrician works to) requires cables and their containment to be adequately supported so they can't be damaged or come loose. In practice that translates to fixed spacing intervals, covered below.
Types and sizes
Three clip types cover almost everything a homeowner's electrician will use on an extension. The difference comes down to whether the conduit is being buried in a chase or run across the surface, and whether the conduit is plastic or steel.
| Clip type | Used with | How it fixes | Where you'll see it |
|---|---|---|---|
| Push-in oval clip (snap saddle) | Oval PVC conduit in a masonry chase | Pushes into a drilled hole or bedded in a mortar joint; conduit snaps into the jaws | New-build first fix, chased socket and switch drops |
| Surface-mount saddle clip | Round PVC conduit on a wall or ceiling surface | One screw through the centre into the wall; conduit pushes under a curved lip | Surface-run cables in garages, outbuildings, lofts |
| Two-hole steel saddle | Round steel conduit, surface-mounted | Two fixing screws, one each side of the conduit | Commercial or heavy-duty surface installs |
The push-in oval clip is by far the most common on a domestic extension. It's a small plastic bridge with two gripping jaws. The electrician drills a hole in the masonry at the bottom of the chase, pushes the clip's leg into it, and the oval conduit snaps between the jaws. Some are designed to bed straight into a wet mortar joint instead of a drilled hole. Either way the conduit ends up held flat against the back of the chase, exactly where it needs to be for the plasterer.
Surface-mount saddle clips do the opposite job. There's no chase; the conduit runs along the face of the wall. The saddle is screwed to the wall first, then the round conduit clicks under the lip. You'll see these in places where chasing isn't worth it: a garage, a loft, a shed, or any run that's allowed to be visible.
Two-hole steel saddles are for steel conduit and you're unlikely to need them on a typical extension. They're a metal strap with a screw hole at each end, used where the conduit has to take knocks or where the installation spec calls for steel containment.
Getting the size right
Clips are sized to match the conduit's external diameter, and the size must match exactly. A clip that's too big lets the conduit rattle loose; too small and it won't snap home at all.
| Conduit size | Typical cable load | Matching clip |
|---|---|---|
| 20mm oval | 1.5mm² to 2.5mm² twin and earth (lighting and standard sockets) | 20mm oval clip |
| 25mm oval | 2.5mm² to 6mm² T&E, or two cables in one run | 25mm oval clip |
| 20mm round | Surface-run lighting or socket cable | 20mm round saddle |
| 25mm round | Heavier surface runs, multiple cables | 25mm round saddle |
Twin and earth (T&E) is the flat grey cable used for almost all UK domestic wiring; the millimetre figure is the cross-sectional area of each conductor, which sets how much current the cable can carry. For most extension work the 20mm oval is the workhorse: it takes a single 1.5mm² lighting cable or a 2.5mm² socket cable comfortably. Step up to 25mm oval where a thicker 6mm² cable is run (a cooker circuit, say) or where two cables share one chase.
How to work with conduit clips
Conduit clips are a consumable, not a skilled material, but there's a right way to use them that keeps the run straight and the plasterer happy.
Start by chasing the channel and offering up the conduit to mark where the clips go. The clip holes are drilled into the masonry at the base of the chase. Push-in clips need a hole sized for the clip leg, usually 6mm, drilled with a masonry bit. Set the clip, snap the conduit in, and work along the run.
The clips should grip firmly. If the conduit slides through a clip with finger pressure, the clip is too big for the conduit or the conduit is undersized, and it will move during plastering. Swap to the correct size rather than relying on the plaster to hold it.
Tip
Fit a clip within 50mm of every bend and every accessory box. Bends are where conduit wants to spring back out of the chase, and the box is where the cable terminates, so a loose tube there pulls the cable about. Clipping tight to bends and boxes is what separates a tidy first fix from a messy one.
You don't need any special tools beyond a drill, a masonry bit, and the clips themselves. Store the packs somewhere dry; the plastic doesn't degrade but a soggy cardboard pack splits and you lose half of them in the bottom of the van. They weigh almost nothing, so a few hundred clips add nothing to a materials order.
Spacing: how often to clip
This is the part homeowners and inexperienced installers get wrong, and it's the whole point of the clip. Too few clips and the conduit moves; the spacing rules exist to stop that.
In a chase, before plastering, fix a clip at maximum 300mm centres (one clip every 30cm or closer). Tighter is better on long vertical drops where the conduit's own weight pulls it down. The 300mm figure is the practical reading of the BS 7671 support requirement for buried conduit, and it's the number electricians work to.
For surface-mounted conduit the run isn't being plastered over, so the clip's job is to stop sag rather than resist a trowel. Oval surface conduit is clipped at around 600mm centres. Heavier round steel conduit can go to 1m centres because it's rigid enough to span further. Always add a clip close to every bend, box, and direction change regardless of the spacing interval.
Warning
Don't rely on plaster, bonding, or adhesive blobs to hold conduit in a chase. A dab of bonding grabs the conduit for a minute but doesn't survive the pressure of a plasterer's trowel passing over it. Mechanical clips at proper centres are the only thing that keeps the run where you put it.
How much do you need
Clips are cheap, so the right approach is to count generously and round up. Work out the total length of conduit on the job, divide by the clip spacing, and add a margin for bends and offcuts.
A worked example for a typical single-storey kitchen extension. Say the first fix has four socket circuits, two lighting circuits, and one dedicated power circuit (a cooker or similar). Allow eight to twelve chased conduit runs averaging around 3m each, which comes to roughly 30m of oval conduit. At one clip every 300mm, 30m needs around 100 clips for the buried runs alone, before you've added any for surface work, bends, or the inevitable handful that snap or get lost.
Buy three packs of 50, or round up further if there's surface-mounted conduit in a garage or loft as well. Over-ordering a consumable that costs a couple of pence a clip is far cheaper than stopping a first fix to fetch more.
If your electrician is supplying materials, this is one line you won't see itemised and don't need to chase. If you're buying materials yourself to hand over, three packs of 50 in 20mm oval covers most extension first fixes with room to spare.
Cost and where to buy
Conduit clips are one of the cheapest items in the whole build. A small pack costs about £1.10 at retail, and bulk packs of 20 or 50 bring the per-clip cost down to a couple of pence each.
Conduit clips (small retail pack)
£1 – £1
Screwfix and Toolstation both stock conduit clips in 20mm and 25mm oval and round sizes, sold loose or in bagged packs, and you can collect from a trade counter the same day. Builders' merchants like Travis Perkins and Jewson carry them alongside the conduit itself, which is convenient if you're picking up a full first-fix list. There's no quality difference worth paying for here; any branded oval clip in the right size does the job. Buy the size to match your conduit and don't overthink it.
External resource
Screwfix conduit and fittings
Conduit, oval clips and saddles in 20mm and 25mm, available for click and collect.
screwfix.com
Because they're so light, delivery is never an issue; clips ride along in any materials order. Buy them with the conduit so the sizes match in one go.
Alternatives
There isn't really a substitute for a clip if you want the conduit held properly, but the choice is between fixing methods rather than products. Some electricians bed the conduit straight into the bonding coat as they go, relying on the plaster to hold it. It can work for short, well-supported runs, but it's the reason conduit ends up wandering off line under the trowel, so it isn't a method worth copying.
For surface work, plastic conduit clips are the cheap option and steel saddles the heavy-duty one. On a domestic extension the plastic clip is almost always the right call; steel saddles only earn their place where the conduit is exposed to knocks or the installation spec demands metal containment. The conduit system as a whole, including when to use oval versus round and how it protects cables from nails and screws, is covered in the conduit guide.
Where you'll need this
- First fix electrics - clips hold the chased conduit straight before the plasterer covers it
- Electrical layout planning - knowing where conduit runs tells you how many clips to order
These fixings turn up at the first-fix stage of any extension, conversion, or rewire where cables are chased into masonry or run on the surface, not just kitchen extensions.
Common mistakes
The errors here are predictable and all of them are avoidable.
Warning
Using the wrong size clip is the big one. A 20mm clip on 20mm conduit grips; a 25mm clip on 20mm conduit lets the tube slide and move during plastering. Match the clip to the conduit's external diameter every time, and check by snapping a clip onto a test length before fitting a whole run.
Not clipping often enough is the next mistake. Spacing the clips at 500mm or 600mm "to save a few" leaves long unsupported gaps that bow and shift the moment the plasterer leans on the wall. Stick to 300mm centres in chases.
The last one is forgetting to clip near bends and boxes. The straight middle of a run might be fine, but the conduit springs out at the bends and pulls about at the box if those points aren't held. A clip within 50mm of every bend and accessory box closes that gap.