Junction Box, Concealed Box or Gang Box: Which One Goes Where

Junction box vs concealed box: the short answer

Junction box vs concealed box comes down to what each box holds. A junction box is where cables are joined, branched or pulled through, closed with a plain cover that must stay reachable. A concealed box is the box set into the wall behind a modular switch board, holding the switches, sockets and plate. Both sit in the wall; they do different jobs.

The confusion is understandable. Both are plastic or metal boxes, both go in during the wiring stage, and electricians sometimes use the words loosely. A third term, the gang box, adds to it: in Indian shops it can mean a concealed modular box, a surface box for switch boards, or simply any box that takes several switches side by side.

We make the boxes behind switch boards, concealed and surface, at our works in Marol, Andheri East, Mumbai. This guide explains each kind of box, where it goes and what it costs, and says plainly which boxes we make and which we do not. Fitting any of them is part of the wiring job for a licensed electrician.

What is a junction box?

A junction box is a closed box in a wiring run where cables meet: it holds the connections that branch one circuit to several points, gives an electrician a place to pull cables through long or bent conduit, and keeps every joint inside an enclosure with a cover that can be opened later for inspection or repair.

In Indian house wiring the common kinds are:

Round PVC conduit junction box with one to four outlets, for straight runs, bends and tees, often at a ceiling light point. Deep junction box for more cables. Square or rectangular inspection box with a screwed lid, in PVC or metal, for a wall or false ceiling.

What makes it a junction box is the accessible cover. A joint inside one can be reached without breaking plaster. A joint buried in the wall, wrapped in tape with no box, cannot, and that is where faults hide. Our types of wiring system guide shows where conduit and boxes sit in concealed and surface wiring.

What is a concealed box?

A concealed box is the plastic or metal box set into the wall behind a modular switch board, sized in modules to match the plate, which holds the switches and sockets on a frame, takes the plate’s fixing screws, and lets the finished board sit flush with the wall instead of standing proud of it.

Its size follows the plate: a 6M plate needs a 6M box. Our VIZA concealed unbreakable box runs from 1/2M to 18M, and the 6M (V615) is ₹118 MRP. The full size list and prices are on our concealed box page, so we do not repeat them here.

A concealed box is chosen before the switches, because once it is plastered in, only the plate can change. A box set crooked makes the plate rock and the screws strip, the snag we most often hear about from flat owners.

Our modular plate sizes guide and the plate size calculator help you count modules for each board.

Junction box vs concealed box: what is the difference?

The difference between a junction box and a concealed box is purpose: a junction box holds cable joints and pulling points behind a plain cover, with no switch or socket, while a concealed box holds switches, sockets and a modular plate at a point you use every day, and its terminals are the switch and socket terminals themselves.

Side by side:

Junction box: Joints and branches Plain cover Ceiling, wall, false ceiling Must stay reachable

Concealed box: Switches and sockets Modular plate Sized in modules Every board in the home

A concealed box is not meant to be a junction box. Electricians commonly loop phase between switches inside a board, which is fine at the terminals; what goes wrong is extra joints and tape stuffed behind the plate, which crowd the box and heat. Our switch board wiring diagram shows what normally sits inside a board.

One more box people mix up: a flex box is a portable extension box on a cord, not a wiring box at all. Our flex box guide explains it.

What is a gang box? Gang box meaning

A gang box is a box that holds several switches or sockets side by side on one board, with “gang” meaning one switch position, and in Indian shops the word is used both for concealed modular boxes and for surface-mounted switch board boxes, which in the modular system are sized in modules (M) rather than gangs.

The terms overlap: a 1 gang switch is a single switch position; a 4 gang board has four. Modular boards are counted in modules instead, where a switch takes one module and a 16A socket two. A 4 way gang box and a 4M box are close cousins, sized to the same plates.

In our own catalogue, the VIZA smart modular surface gang box is a surface-mounted box, not a smart device, sized from 1 way (V641) to 18 way (V649). It takes the same modules and plates as a concealed board, for walls where the wiring runs on the surface. Our gang box and modular plates page shows the range.

Our 1 module and 2 module switches guide explains how modules are counted on a board.

What are the types of gang boxes?

Switch board boxes come in four common types: concealed plastic boxes set into the wall, concealed galvanised sheet metal boxes for sites with rough handling, plain surface boxes fixed on the wall, and surface gang boxes styled to match modular plates, each sized in modules or ways to fit the plate.

Our VIZA range covers all four:

Concealed unbreakable V611–V619, light and rust-free. Concealed G.I. sheet V621–V629, sturdier on site. Surface unbreakable white V631–V639, ₹60 to ₹260. Smart modular surface gang box V641–V649, ₹65 to ₹265.

For a new build with concealed wiring, the plastic concealed box is the usual choice. A surface box suits rented homes and walls that cannot be chased.

Where do junction boxes go in a house?

Junction boxes in a house commonly go at ceiling light and fan points where cables branch, at conduit bends and along long runs where cables must be pulled through, above false ceilings where several light points meet, and anywhere a circuit splits, always where the cover can be opened later.

Typical places: Ceiling light point Fan point Long conduit runs False ceiling grid Outdoor or balcony runs.

In a false ceiling, plan an access panel or a light fitting that can be removed near each junction box. A box sealed above a gypsum ceiling is reachable only by cutting it. For outdoor and balcony runs, the box needs a cover that keeps water out; a junction box with water in it is a common cause of MCBs tripping in the rain, as our guide to an MCB tripping again and again explains.

Ceiling roses do a similar job at a pendant light; our guide to the ceiling rose explains the connection.

Can joints be made inside a switch board box?

Joints inside a switch board box are common practice only as clean loops between switch terminals, or with proper connectors where a circuit must branch at the board, with nothing crammed behind the plate; taped twisted joints pushed into a crowded box are a frequent cause of heat, sparking and faults at switch boards.

What good looks like: loops at the terminals proper connectors room to spare in the box. What bad looks like: twisted wires and tape a box too small for its cables plate bulging out.

If a board needs many joints, a bigger box or a separate junction box is the cleaner answer. Insulation tape covers a joint; it does not make one. Our guide to electrical insulation tape explains what tape is for.

Heat at a board usually starts at a loose or crowded connection. Our guide to a switch getting hot or socket sparking covers what to do when it does.

Which size concealed or gang box do you need?

The concealed or gang box you need is the same size as the plate it carries, counted in modules: a 4M plate needs a 4M box and a 6M plate a 6M box, with the 8M available as a horizontal or square box, so the number of switches and sockets on the board sets the box before anything else.

Count the board: switch = 1M 6A or 16A socket = 2M regulator: check its module size, then round up to the next plate size with a spare module for later.

Our modular switch board price guide prices complete boards with the box included.

Plastic or metal box: which is better?

A plastic box is the usual choice for homes because it is light, does not rust and is easy to set in plaster, while a galvanised metal box is sturdier against rough handling and heavy wall chasing on site, and both carry the same modular plates, so the choice is about the site rather than the switches.

Plastic (unbreakable) Light, rust-free, the common pick for homes and offices. Our 6M concealed box is ₹118.

G.I. sheet metal Galvanised steel, chosen by some contractors for heavy-duty sites. Our 6M (V624) is ₹170.

For junction boxes the same split applies: PVC with PVC conduit, metal with metal conduit, as the wiring system dictates.

Boxes and enclosures for household electrical accessories have their own Indian Standard, IS 14772, brought under compulsory certification by the Electrical Accessories (Quality Control) Order, 2023. Our guide to IS codes for electrical products lists it alongside the standards for switches and sockets.

Which boxes do we make, and which do we not?

We make the boxes behind switch boards: VIZA concealed unbreakable boxes from 1/2M to 18M, concealed G.I. sheet metal boxes, surface unbreakable boxes and smart modular surface gang boxes from 1 to 18 way, plus MCB boxes; our catalogue does not list round conduit junction boxes, which you buy with the conduit.

VIZA V615 is a 6-module concealed unbreakable box with an MRP of ₹118. VIZA V649 is an 18 way surface gang box at ₹265. Both are on our VIZA gang box page.

One catalogue name can confuse: our VIYONA 3 in 1 switch socket is listed both as the 3 in 1 universal switch socket combined (159) at ₹150 and as the 3 in 1 with junction box (160) at ₹175, and the 5 in 1 likewise (161 at ₹250, 162 with junction box at ₹300). That is a catalogue name for the unit with its own box, not a conduit junction box. Ask your dealer if unsure.

We do not list round conduit junction boxes; your electrician supplies those with the conduit. For the distribution board itself, see our MCB box size list.