What Are the 4 Types of Wiring? Cleat, Conduit, Casing, and Concealed Systems
When electricians or engineers refer to the “types of wiring,” they are usually talking about the method used to install and protect the conductors, not the conductors themselves. Four classical methods cover the territory: cleat wiring, casing and capping wiring, batten wiring, and conduit wiring. Some are nearly obsolete in modern construction; others have evolved into the systems we still install today. Understanding all four gives you historical context for old buildings and a vocabulary for specifying new ones.
1. Cleat Wiring
Cleat wiring is the oldest of the four. Insulated cables are run in straight lines along walls and ceilings, supported every meter or so by porcelain, plastic, or wooden cleats that grip the conductors and hold them away from the surface. The cables are completely exposed to view and to the surrounding air.
The advantages are simplicity and speed. A cleat-wired installation can be put up by a single worker with hand tools in a fraction of the time a concealed installation requires. Faults are easy to locate because the entire run is visible, and modifications take minutes rather than hours.
The disadvantages are equally obvious. Exposed wiring is vulnerable to moisture, mechanical damage, rodents, and curious fingers. Aesthetically it looks raw, which is why cleat wiring today is almost entirely restricted to temporary installations, construction site power, and unfinished spaces like warehouses, sheds, or workshops. Many regional electrical codes prohibit it outright in occupied residential buildings.
2. Casing and Capping Wiring
Casing and capping is the next step up in protection. The cables run inside a rectangular wooden or PVC casing, which is essentially a U-shaped channel fixed to the wall. A separate cap or lid snaps over the top of the casing, enclosing the cables completely. The cap can usually be removed for service.
This method was common in the early to mid twentieth century, particularly in residential buildings where exposed cleat wiring was considered too crude. Wooden casing has largely disappeared because of fire concerns, but PVC casing-and-capping is still used in some parts of the world, especially for surface-mount retrofits in older buildings where chasing walls is impractical.
Casing and capping protects against incidental contact and minor mechanical damage, and it allows the cables to be replaced without opening the wall. It does not, however, offer significant protection against fire, water, or determined damage, and it is generally considered an intermediate solution between cleat wiring and full conduit installation.
3. Batten Wiring
Batten wiring uses wooden battens, typically half an inch thick and one or two inches wide, fixed flat against the wall surface. The cables are then clipped or stapled directly to the batten. Some variants of batten wiring use a metal clip system instead of staples, but the principle is the same: the batten provides a continuous, level surface that keeps the cable straight, off the wall, and away from masonry that might damage the insulation.
Batten wiring was a popular method for surface-mount installations in the early and middle decades of the twentieth century. It is cleaner-looking than cleat wiring and faster to install than casing-and-capping. The main drawback is that the cables remain exposed, so all the same vulnerabilities to damage, vermin, and weather still apply.
You will still see batten wiring in some agricultural buildings, older industrial spaces, and in low-cost residential construction in some parts of the world. In most jurisdictions it has been displaced by surface-mount PVC conduit, which offers similar speed and aesthetics with much better protection.
4. Conduit Wiring
Conduit wiring is the modern dominant method. Conductors are pulled through a rigid or flexible tube made of metal or PVC, which protects the wires from mechanical damage, moisture, and fire. Conduit can be installed exposed (surface conduit) or hidden inside walls, floors, and ceilings (concealed conduit).
Several conduit subtypes are common. Rigid metal conduit (RMC) is heavy-walled steel pipe used where maximum protection is required, such as industrial environments or exposed exterior runs. Intermediate metal conduit (IMC) is lighter and easier to bend, but still rugged. Electrical metallic tubing (EMT) is the thin-walled steel conduit most widely used in commercial construction. Flexible metal conduit (FMC) and liquidtight flexible conduit handle the last few feet to motors, transformers, and any equipment that vibrates. PVC conduit is non-metallic, corrosion-proof, and the standard for underground runs and damp environments.
Within the conduit family, modern residential construction in North America has largely shifted away from conduit for living-space wiring and now uses NM-B cable run directly through stud bays. Conduit remains the standard for commercial work, industrial work, and any installation where future wiring changes are anticipated.
Concealed vs Surface Installation
Cutting across the four categories is the question of whether the wiring is exposed or hidden. Concealed wiring runs inside walls, above ceilings, and under floors, with only the outlets, switches, and fixtures visible. Surface wiring runs on top of finished surfaces, contained in surface-mount conduit or raceways. Concealed installations look cleaner and protect the wiring better but cost more to install and significantly more to modify. Surface installations are faster and easier to change but less attractive and more exposed.
Choosing a Wiring System
The decision usually comes down to the building type, the local code, the budget, and how much future flexibility you want. New residential construction in North America almost always uses concealed NM-B cable. New commercial construction almost always uses concealed EMT conduit. Industrial work uses RMC or IMC conduit with appropriate fittings. Older buildings being retrofitted often use surface-mount PVC conduit or surface raceway to avoid opening walls.
The four classical wiring categories sit on a continuum from minimal protection to maximum protection. Most modern installations land at the maximum end, and for good reason: the cost of protecting the cables once during construction is far lower than the cost of repairing damage or causing a fire later.
