How Do You Run Electrical Wires Under the Floor?

When installing a home theatre system or running a new phone jack stringing the wires along the floor may seem like an option; however, snaking the wires under the floor or in the walls is the best option. It’s safer for you, and the wires protect them from wear and tear.

When trying to install the wires in walls before the drywall or under the floor before laying tiles is a piece of cake task compared to installing the wires after the construction is finished. Although, with the proper planning and required tools, you can finish the task without effort.

How Do You Run Electrical Wires Under the Floor?

Preparing the Workspace

First, before doing any work, you will need to check the local building codes to avoid any violations. According to most local codes, homeowners can install low-voltage wiring, for example, speaker wire, computer network cable, and phone lines; however, you always need to check.

Selecting the proper cable or wire, you will need to ensure that the cables or wires you are running, whether inside the walls or under the floor, meet local standards. The standards include fire and building codes like CMR, CM, and CMP for computer networks and CL3 and CL2 for speakers wiring.

Turning off the breakers in your electrical panel or box is necessary before doing any electrical task. You will be drilling into the walls and floors, so there is a chance that you will drill into an existing wire; if the electricity is flowing, this can cause electrocution and harmful consequences.

Keep the newly installed wires away from the phone, computer, and speaker wires as much as possible. As a result, this will keep your wires safe and prevent interference. Choose the walls to which you are installing the wires if you can, and try to install your wires into interior walls instead of exterior ones to avoid insulation and braces.

Plan your Approach

Scan the site you will be working on using your eyes, and determine where the old wires and the existing electrical outlets could exist. As a result, you can avoid hitting the old wires, and the safe distance will prevent any interference between the new and old wires.

The following scan for the location should be from the basement, crawlspace, or attic to ensure it’s free of plumbing or wiring and it’s accessible. A great tool to use when installing wires is a metal-detecting stud finder; you can scan the floors and walls for any obstacles, like copper pipes.

After mapping out your route, you can now easily calculate the cable or wire you need, and you can do this by measuring from the point of start to the end of the route. An important thing to keep in mind is the cable length wasted in connections and to add a 10% for unexpected issues or obstacles.

Installing the Wires

If you have a concrete screed, you should know that your wires must be laid in a steel pipe or corrugation; this option also works for writing under a wooden floor. The steel pipes protect your cables and wires from rodents and ignition; wires can’t be laid without protection.

If you are mounting your wires or cables on or behind combustible materials, you must have cables made from non-combustible materials, for example, VVGNG-LS. In addition, when laying the wires, you must ensure that they are straight and don’t have twists to avoid tearing.

If you connect wires, the connections must be in junction boxes above the floor; however, if you cannot meet this rule, you can use a switch box with a cover for inspection on the floor. After finishing, you will need to mark this inspection box on the diagram to locate it later quickly.

When installing the wires inside the corrugation, you must ensure that the corrugation is not filled with more than 35%-40%. The turns are not specified in any document; however, for your convenience, there should be no more than two turns, as replacing the cables in the corrugation will be tough.

In wooden floors, you directly create holes in the lags to allow the passage of the corrugation; in addition, you will need to apply an anti-burning product to the wood. The standard screed thickness over the corrugation must be at least 30 centimeters; overlapping the intersections will require a more screed thickness.

What Are the Advantages of Wiring Under the Floor?

The first thing that comes to mind when installing wires under the floor is safety, as it is impossible you have the chance of hammering a nail into current-carrying conductors or wires as you might if wires are installed in walls. Therefore, there is no chance of electrocutions or electrical shocks.

The cost of installing wires under the floor compared to installing the wires in the walls is very low, as you avoid increasing wires length by stretching the wires around the perimeters of the rooms. In addition, laying the wires under the floor allows you to follow the shortest route or path, saving the cables’ length.

When comparing the cost of installing the wires under floors and inside walls, a point to keep in mind is the height of the outlets and sockets. So that the wiring under the floor has an economic advantage in that the sockets and outlets’ height is between 20 to 30 centimeters.

It’s an easy task, and you don’t have to go through any complicated steps; you will need to lay the wires into the corrugation, for example, the steel pipes. Then, you will securely fix them on the floor and connect the wires’ ends to the connection points. The last step is to pour the screeds, which can be the only exception.

What Are the Disadvantages of Wiring Under the Floor?

The tasks can be a bit complex regarding replacing and repairing the wires. For example, if a chain in your wiring breakers for any reason like installation damage or rodents. Because it will be hard to find the area with the problem in the cable, all you can do is pull out the cable and replace it.

The cost of repairing is high as you will need to break into the screed, replace the corrugation, and replace the whole cable. As a result, you should be careful when installing your wires under the floor to install everything correctly to avoid any near future replacements.


When to Use Under-the-Floor Wiring?

If you have a wooden house, you could face some inconveniences when installing electrical wiring, as you will either choose retro wiring, which has high costs, or try special channels for cables that will ruin the wooden appearance of your house as they don’t complement it.

Therefore, the best choice is to install the wires under the floor so you can hide the cables and deliver electricity to all spaces you need in the house. Installing the wires under wooden floors is easy; you could create holes in the lags, run the corrugations through them, and then lay the wooden floor.

Another scenario in that you might need to go with under-floor wiring is if you are buying an apartment in a new building. New apartments are often rented without being repaired, where the cables are laid in corrugations on the floor.

You can choose not to chip walls, install the cables, and instead fill in the screed and connect the cables to the outlets and sockets you want. This will save you effort and money and make you avoid violating the integrity of the walls.


To summarize, you can run wires under the floor by following the suitable plan for your area and preparing the required tools. The process can be done through several steps; first, you will need to check your local fire and building standards. Next, select suitable cables for your task, for example, if you are installing the cables behind or on combustible materials.

The cable sheath must be made of non-combustible materials to avoid melting and in case of any fires. Safety before anything when dealing with electricity, you should power off your circuit breakers, so in case you drill into a wire, you will be safe and not electrocuted. Next, plan your approach by scanning the place for wires, plumbing pipes, and electrical outlets.

Draw the route you will follow and measure the distance to determine the length of cable you will need. In addition, you should add some extra length for connections and about 10% for any obstacles you face. Finally, lay the wires according to the abovementioned steps, and you are ready to go.

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