Despite the fact that a junction box is often crafted from diverse types of metals, it does not often apply for specific purposes. In most cases, the plastic enclosures fill the gap of need, as they are made for general application as well as specific uses. And it’s for this reason, that they are very common in the market of enclosures.

Electrical boxes are very important when installing outlets and inlets of electrical lines. They are essential for safety measures. Through them, we are safe from electrical shock. These boxes come from various materials for example plastic or metals. Each of these materials has benefits that make you choose one over the other. Below, you are provided with the advantages and disadvantages of using plastic boxes.


  • Cost-effective

PVC junction box are available in the market at cost-effective values. You get to receive quality services at a considerable value. Moreover, during installation, they are less demanding when it comes to accessories, unlike the metal enclosures.

  • Versatility

Plastic enclosures are versatile in various ways. For instance, they are applicable for both indoor and outdoor uses with few limitations. Polycarbonates plastic which falls in the category of heavy-duty is highly resistant to extreme weather elements. Thus they can be installed indoor or outdoor. Also, due to their tough and strong structure conformation, they are resistant to strong impacts that a metal enclosure will not survive.

  • Multifunctional

Electrical receptacle boxes are available in different designs. They are made specifically to fit various needs that involve electrical installations. For instance, the strong and tough plastics are used when fixing light fixtures on the wall or ceiling.

They are very strong and firm, thus they are able to resist the weight of the light fixtures. Moreover, they are very durable and resistant to corrosion hence you can use them to install permanent fixtures.

Other uses include installation of light switches, whether high voltage or voltage switches. When you need to fix a power socket on a wall they will still come in handy. Hence they have unlimited applications with each use having a specific design of the box that offers the best performance.

  • Non-conductive

Plastic enclosures have no electric conductivity thus they cannot transfer current when in contact with a live cable. Having such enclosures in the house is a good choice considering electrical issues that may arise anytime. What makes these enclosures the best option is the fact that they don’t need grounding.

  • Easy to mount

Mounting an enclosure on a ceiling or high on a wall is quite a simple job. The challenge comes in when the enclosure is heavy. But with plastic enclosures, they are very light. thus you can easily hold it with one hand and drive in the screw or nail with the other hand. some of the boxes come with a nail which is pre-attached, making your job even much simpler.

When considering the depth to install the plastic receptacle, they have side markings to make your work easier. You just check the markings and use their measurement (e.g. 4x4 junction box) to estimate the size of depth you will need.

When you are installing the box for the first time, on a wall, you will need “new work” types of boxes. But if you are redoing your previous installation, you will need “old work” types of boxes.

These boxes come with ear-like structures that flip out during installation to grasp the backside of the wall when you are screwing the box in place. This makes your work easy and fast, as you will require less effort to hold the enclosure in place when driving in the nail or screws.

  • Allow for modification

At times you may realize some accessories of your metal enclosure are out of place. Considering the box is plastic, you can easily melt it or cut it into a form that fits your enclosures best. Thus plastic enclosures can easily fir what you need to install on them compared to when dealing with a metal box.

  • Aesthetically appealing

They have a smooth and clean surface that complements the place of installation. Depending on your love for colors, you can get this box in diverse ranges of colors. But the most common type is glossy white. Therefore, they are great when doing your final touches or finish in a room. Just ensure you pick the color that blends well with your wall color.

  • Strength and durability

For strength and durability, you will need high-density junction boxes made of polycarbonate. They are tough and resistant to heavy blows. This means the general structure and nail brackets are all made of this material. Therefore, you can drive in a nail during installation without the fear of breaking the box.

  • Have cable clamps

The plastic junction enclosures come with cable clamps which are incorporated in the box. In most cases they in shape of small spring tab. They serve to hold in place the cable snug during installation into the enclosure. This makes the installation process quite simple and fast. This is unlike their metal counterparts whose cable clamps are external. 

  • Non-magnetic

The plastic junction enclosures are non-magnetic. Thus they are best when dealing with electrical appliances that are sensitive to magnetic interference. This is unlike metals which are not only conductors but also good at channeling magnetism.

  • Waterproof

When enclosures are in need in moist environments or where they are susceptible to water, plastic is the best option. They are not only waterproof but cannot be corroded by water. This is unlike their metal counterparts. Also they are handy when installing underwater enclosures, as they guarantee the best durability and safety.



  • Some breaks easily

When you are dealing with light and less dense plastic enclosure, they can easily get on your nerves. They are made of plastic all-round, this means the nail brackets, the box structure, and additional features. They easily break during installation and even when uninstalling. This feature makes them very expensive. This is because once the nail brackets break off, you will have to replace the whole box.

The screw ports of the boxes are also vulnerable; the threads that hold the screw in place are made of plastic. This means they can easily get damaged. In some other cases, they get worn-out fast after several screwing and unscrewing of the external switch or socket. More often we get tempted to use the old screws in case we lose the box screw. Using larger ones will end up destroying the threads and even break the mounting holes.

  • Unreliable

They are unreliable at certain circumstances, e.g. when you need to replace an old junction metal box with metal conduit. The plastic enclosure is unreliable as it cannot be used with metal conduit. There are various electrical installations which rely only on the metal conduit, in such situation; you have to abandon your favorite plastic enclosure.

When it comes to outdoor installations, some plastics are reliable, and this is only if the wiring system runs within a wall. But there are certain installations that require the wiring exposed, such as some garage switch. In this case, it’s only the metal enclosure that can apply here.

  • Safety

Plastics are best when there is a short circuit or problem with the electrical system. This is because they are nonconductors; hence they offer you protection from shock. But in case of a fire breakout or an overheated socket, the plastic will burn and melt, exposing live wires. This is very dangerous as the electric lines may connect causing a fault that may add more damages. In such circumstances, metal boxes are best as they are heat resistant even during intense fire.

Plastic boxes work well when installing light and small fixtures on the ceiling. But when it comes to heavy and huge fixtures, the metal boxes offer more firm support. Additionally, one will have more faith when a light fixture weighing several pounds is supported by a metal box over their head rather than plastic. When installing heavy fixtures like the big ceiling fans ensures the mounting brackets are specific to this role.

Plastics get broken easily when they receive a heavy blow. For example, it’s much safer to have a metallic enclosure on the roadside than plastic. Both they will get damaged during an impact, but the metallic enclosure will still protect the live wires. But with plastic enclosure, it will break exposing the live cables which are more dangerous.

  • Chemical resistance

Plastic enclosures have limited resistance to chemicals as compared to their metal counterparts. For that reason, they are not to be exposed to alkalis or solvents as they have no ratings over them. But despite that, it has a tolerance to mild acids.

Also, some of the plastics become fragile with long exposure to sunlight. This compromises their structure, making them unsafe.

 Plastic vs. Metal electrical boxes

Plastic boxes general application

Plastic is becoming a popular material for making electric boxes. Most types of plastics are PVC (polyvinyl chloride and polycarbonate. They are inexpensive, light in weight, and easier to work with. It’s much easier to punch holes through plastic during installation.

However, plastics can melt when exposed to intense heat but still it will not conduct electric current. To give you an easy time during installation, some have clamps which are in-built. This lowers the overall cost of the project.

Metal boxes general application

They are also popular and were the first type of electric boxes. This is long before the invention of pvc junction boxes. The metal material box is featured with very strong overall structure, fireproof and can withstand intense heat without melting providing the highest level of safety to wiring applications.

When it comes to personal installation, they are somehow intricate to deal with. This is because they have sides and rear knock-outs which are in need of supplementary clamps. This causes an additional cost in the project budget.

Moreover, the metal boxes have sharp edges which can give you an intense cut if you are not careful. It is important to wear protective gloves when dealing with them.


Recommendation for plastic boxes

The best application of Romex/NM cables is with a plastic box when wiring leads either in/out of the box. But the electric code is not in support of using Romex/NM cables with electric plastic box.  The sole requirement is the need for grounding during the connections.

When it comes to metal sheath wiring, plastic boxes are out of the picture. This is unless grounding is addressed in some way. Also, for grounding, the metal sheath wiring relies on attachment onto the metal box. Use of plastic boxes in this situation with no grounding posses a great risk to the users.

Recommendation of metallic boxes

When you are dealing with metal-sheathed cable, the metallic boxes are the best option here. This applies the same with when dealing with metal conduit. This is because; in both cases grounding is a must. This is the only way to ensure the safety of wiring system.

When installing a wiring system which is on the wall surface rather in, you will need metal boxes. They are assuring in safety as compared to the plastic boxes. Also, it’s because the metal conduit is a must in such cases since the wire is exposed.

Romex/NM cables are also compatible with metal boxes, but in such a case, special precaution must be taken during grounding. When an attached device and the metal box touches, these create a complete grounding. Therefore, the only time Romex/NM cables are applicable with a metal box is after the attachment of grounding wire with a screw on the box.

Other comparisons

When you need to personally address home remodeling without the use of expert or professional help, plastic boxes are the best. They are very simple to use and pose fewer risks. On the other end, metal boxes are somehow intricate; chances of making a mistake during connections are high. Thus, they are less common in such circumstances.

Despite the great features that accompany metal boxes, they are quite expensive. Using them solely in a project will raise the budget cost. Thus a plastic junction box essential, as it is inexpensive and provide the safety measures that metal box do, except when grounding is a must.