Most outdoor cameras do not fail because of rain. They fail because someone joined a camera cable in a box that was too small for the connector, or sealed an entry that had a plug jammed through it. Choosing a junction box for security camera wiring is a sizing problem before it is a waterproofing problem: the enclosure has to swallow a connector stack and a bend radius, and only then hold a seal.

This guide covers the camera cabling patterns, the arithmetic that decides whether a connector fits, and the four places water actually enters a camera installation — one of which is not the box at all.

Three Cabling Patterns, Three Different Boxes

Camera systems need different entries because they carry different cables. Match the box to the pattern before you look at IP ratings.

Figures are typical values — measure the jacket on the drum you were supplied. A coax-and-power analogue drop or a power-only Wi-Fi camera fits a compact sealed enclosure with no compromise; anything with a factory-fitted RJ45 needs space and a plan.

The RJ45 Problem

An RJ45 plug body is about 11.7 mm wide and cannot be reduced. The most common compact box we sell, the F1 series mini junction box, seals cable ranges of 3–6.5, 5–8 and 7–10 mm across eight order codes — perfect for a 6 mm Cat5e jacket, and impossible for the plug moulded onto the end of it. A PG9 gland has the same limit: it clamps 4–8 mm of jacket and nothing wider will pass.

There are only three honest answers:

1. Cut and re-terminate inside the box. Pass bare cable through the gland and crimp a new RJ45 on the stub — the cleanest result and standard practice on commercial installs. It needs a crimp tool and about 50 mm of clear depth.
2. Use a split gland. Two-piece designs clamp around a cable that already carries a connector. Retention is lower than a solid gland and the seal relies on the joint between halves, so reserve it for sheltered positions.
3. Keep the connector outside. Terminate to a bulkhead coupler or a short patch lead and let the box house only the splice — more parts, but no re-crimping on site.

What does not work: drilling the entry out and wrapping the plug in self-amalgamating tape. The tape becomes the only element holding the rating, and it has no rating.

Sizing the Box from What Goes Inside

Interior volume is decided by three things, and only the first is obvious:

• Bend radius. Installed Cat6 is commonly specified at 4 × cable diameter. For a 7 mm cable that is 28 mm of radius, so roughly 56 mm of free depth to turn without kinking.
• The connector stack. A mated RJ45 pair is about 45 mm long once the boots are on. Add 50 mm of service loop and you have used most of a small box.
• Anything active. A PoE splitter dissipates a few watts in a sealed plastic box with little surface area. Keep active devices out of the smallest enclosures.

Our JX-AG high-end waterproof junction box runs from 95 × 65 × 55 mm to 280 × 190 × 180 mm with IP67 (1 m immersion) and IK08 impact resistance. The smallest size gives about 0.34 litres gross — call it 0.24–0.27 litres usable once walls, bosses and lid are accounted for. That is enough for a splice and a loop, not enough for a splitter and a coil of surplus cable. Treat usable volume as 70–80% of the published exterior dimensions and the choice usually makes itself.

Where the Water Actually Gets In

1. The cable entry. The gland seal on the jacket, not the box, is usually the failure — an undersized jacket leaves the seal slack.
2. The lid gasket. Camera boxes get opened more than any other enclosure, because installers adjust angle and focus. A gasket pinched on the first visit leaks for the next five years — tighten diagonally and stop when the gap closes.
3. The camera base joint. The fourth joint nobody owns. The box may be IP67 and the camera IP66, but the interface between the camera plate and the box face is sealed by the camera’s gasket — and only if the plate lands on a flat surface.
4. Condensation. Not a leak at all. A sealed box with a day/night swing pumps moist air through micro-paths and drops it out on the coldest surface, usually the camera metalwork. Our guide to condensation in junction boxes has the arithmetic; the fix is a breathable vent plug.

Match the Box Face to the Camera Base

Camera mounting plates are usually round and often wider than a compact box. Measure the plate diameter first: a 100 mm plate on a 95 × 65 mm box leaves the gasket edge hanging over air, and silicone will not seal an unsupported gasket. Step up to a size that supports the full ring, or mount the camera on its own bracket and use the box as a cable chamber behind it. Flatness matters as much as width — moulded ribs, part lines and screw bosses all create a path under the gasket, so a plain flat lid face is worth more than an extra millimetre of wall.

Plastic or Metal Under a Camera

Plastic is the default for a reason: no corrosion, no earth bond to maintain, no paint to chip, and the box does not become the tallest thing on the mast. ABS covers most wall-mounted work; the JX-RA plastic waterproof junction box adds CE and RoHS documentation, internal PCB or DIN rail mounting points, and pre-moulded 25 mm or 36 mm holes across eleven sizes. Metal earns its place in two cases: where impact risk exceeds IK08, and where the installation demands a metallic earth path. In the second, the gland must be an EMC type with the shield bonded at the box.

Gland Sizing for Camera Cables

Select on jacket diameter, then check the hole. From our standard nylon cable gland range: PG7 clamps 3.5–6.5 mm (needs a 12.6–13.0 mm hole), PG9 clamps 4–8 mm (15.3–15.5 mm), PG11 clamps 5–10 mm (18.7–19.0 mm), PG13.5 clamps 6–12 mm (20.5–21.0 mm). A 6 mm Cat5e sits in a PG9; a 7.5 mm Cat6 needs PG11. For the analogue side in more depth, see our article on cable glands on CCTV systems.

An Installation Sequence That Keeps the Seal

1. Drill the fixing holes and the entry before the box goes on the wall — drilling a mounted box fills it with swarf.
2. Deburr the entry, fit the gland from outside with its washer, locknut inside.
3. Mount the box, then feed the cable with a drip loop below the gland.
4. Terminate, loop the surplus within the bend radius, keep the connector off the lid.
5. Fit the lid with its gasket seated in the groove, tightening diagonally in two passes.
6. Fit the camera plate last, against a clean flat face rather than grit from the wall.

Conclusion

Size the junction box for security camera work in four steps: count the cables, measure the largest jacket, decide whether a plug has to pass, then allow for the bend radius and connector stack. Only then does the IP rating decide — and the assembly is only as sealed as its worst joint. A camera on an IP67 box with a 2 mm gap under its base plate is a wet camera.

Send us the camera model, the cable type and the mounting surface, and we will come back with the enclosure size, the entry list and the gland sizes — contact our team.

Frequently Asked Questions

What IP rating does an outdoor camera junction box need?

IP65 minimum for a sheltered wall, IP66 for direct rain, IP67 where the box can stand in water or take a pressure wash. The camera, the entries and the base joint each carry their own rating.

Can I put an RJ45 connector inside a small junction box?

Only if the box has depth. A mated RJ45 pair with boots is about 45 mm long and the cable still needs a bend radius near 4 × its diameter. Below about 70 mm internal depth you will pinch the cable against the lid.

Do I need a junction box if my camera already has a pigtail?

The pigtail gets you a short lead, not a sealed joint. If the connection is outdoors, the joint still needs an enclosure — otherwise the coupler sits in rain and oxidises within a season.

How do I stop condensation inside a camera box?

Equalise pressure instead of trying to make the box airtight. A breathable vent plug moves about 325 ml/min at 0.07 bar while holding IP68 through its O-ring, so moisture leaves with the air instead of condensing on the camera body.