How to: Running Ethernet Cable Through Walls
Written by Dave Harris, trueCABLE Technical Specialist, BICSI INST1 Certified
If you are installing new data cabling in your home or business, you want it to end up looking complete and professional. That’s why we recommend terminating installed cable to a keystone jack, and install the jack into a wall faceplate. In fact, we have a whole other blog just about installing jacks and wall faceplates. In that article, an Ethernet cable is presented extending out through a hole in the wall. This article will provide some techniques for getting the cable inside the wall, and discuss some tools to make the job easier.
Anatomy of a Residential Wall
Since we are installing our cable inside the wall, we need to know a little about how residential walls are constructed. In general, a wall will consist of wood framing covered on both sides with wallboard, also called “sheetrock.”
The wood framing is typically built using 2 by 4 lumber. There is a horizontal board that sits up against the ceiling joists called a “top plate.” Sometimes the top plate is two boards thick. Along the floor is another horizontal board called a “sole plate.” The top plate and the sole plate are separated by vertical boards which are called “studs.” The studs are positioned at each end of the wall and vertically every sixteen inches on center. The enclosed space between two wall studs is often referred to as a “bay.”
Unless your home is more than about seventy years old, the framed wall was covered with a flat, compressed gypsum product called “sheetrock” or “wallboard.” Then the wallboard was finished and painted.
Know Your Wall
As you might expect, before you cut into a perfectly good wall, you need to make sure that you are just cutting the wall board and not something vital inside the wall. Residential walls can contain electric cable and plumbing pipe, among other things.
You also need to make sure that you are not trying to cut into a wall stud. Use a stud finder to locate the positions of the studs behind the wallboard. Some stud finders are available that also sense the presence of cable, conduit or pipe inside the wall. This would be a great application for that.
If you can access an unfinished attic above the wall, you can actually see the top plate if you look between the attic’s floor joists. If possible, inspect the top plate for wires, pipes, or anything else that might be going into the wall.
If you can see the floor that the wall sits on while looking up from an unfinished basement, you can’t see the sole plate, because it is above the floor. But you can often see framing nails protruding through the floor where the sole plate was fastened to the floor. In any case, careful measurement will be needed to find the wall from the basement. Make sure, if possible, that no utilities are entering the wall from below in the area you will be working.
We’ll discuss methods for pulling cable in walls as we introduce the tools commonly used to accomplish it.
Tools and Methods
Ship Auger Drill Bit
In order to access the interior of the wall where the cable will be installed, it will be necessary to drill a hole either down from the attic or up from the basement. This hole should be 7/8 inch in diameter, if you ever want the option to put more than one cable through the hole. If you don’t care about that, a 1/2 inch hole should suffice. You have several options for getting a 7/8 inch hole. Spade bits, Forstner bits, and even holesaws can do the job, but it takes some time and effort. If you can find a 3/4 inch or larger twist drill bit, it will work, but it usually leaves a hole that needs to be cleaned out. What you really want is a ship auger bit. It has a threaded tip which pulls the bit through the wood with minimal effort. It makes a precise, clean hole, and it makes it fast. These bits are a little expensive, but it’s usually worth the investment.
A fish tape is a long steel tape coiled up inside a ring-shaped container that also acts as a reel. The tape’s combination of flexibility and rigidity makes it useful when guiding it through unseen pathways. But fish tapes are often found to be too floppy for most residential work, especially compared to glow rods and flexible drill bits. Fish tapes are extremely useful for pulling wire and cable through conduit, which in my experience accounts for most of their use.
Fish tape. Image courtesy of Northern Tool.
Glow rods are long fiberglass sticks used for pushing cable from one location to another. In my experience, they are an essential tool for this type of work. They get their name from the fact that they will glow in the dark, which is a really nice feature while working in ceilings, crawl spaces, and other low-light areas. They are mostly rigid, which is necessary for guiding the cable path, but they are also flexible when needed, to allow for changes in direction.
The way these usually work is to tie-and-tape a pull string to the glow rod, and then use the glow rod to guide the pull string to the desired destination. For an in-wall installation, it is usually best to start at the small hole in the top or sole plate, and push towards the outlet opening. Since the outlet opening is larger, it is easier to find the glow rod inside the wall, and you can use your hand, a coat-hanger hook, or long-nosed pliers to retrieve the glow rod and pull it and the pull string through.
Flexible glow rod. Image courtesy of Jameson Tool.
What if you have a multi-story dwelling and you need to run a cable from the attic all the way to the basement? You could drill holes through all of the sole plates, top plates, and floors; but that would require opening and patching wallboard in multiple places. Instead, look for the plumbing stack. The stack is a vertical plumbing pipe that extends from the basement of your home to the roof. The pipe is of course cylindrical, but the holes cut into floors for it are usually square. That means that at the corners of the opening, there are open penetrations between the floors extending the length of the stack.
No demolition, drilling or patching sounds great, but how do you actually get a pull string down there? A fish tape won’t work. It’s too flexible and there’s no way to control it when you can’t see it (except when it’s in conduit). Glow rods can be useful, but only if you don’t have to go too far and all of the openings are perfectly lined up. Some people have success using a plumb bob to lower a pull string down the side of the pipe. But, the plumb bob usually has to be pretty small while still providing enough weight. Also, the openings still have to be lined up perfectly.
I’ve had some luck in these situations by dropping a chain. You need a chain long enough to reach from the roof to the basement floor. It should be made of steel since it needs some weight. The links in the chain should be as small as possible. The smaller the chain link, the smaller the floor opening that can be navigated. Start sending the chain down next to the pipe. When it gets to the floor below, it might just continue straight down all the way to the next one. But it might not. If the openings don’t line up, or the chain is even slightly swinging like a pendulum, it’ll hit the floor. But when it does, and you continue to lower the chain anyway, the chain will start to pile up and coil up and spread out. As soon as a link of chain finds itself over an opening, it will fall through, with the falling weight pulling more chain down with it. In this manner, the chain will actually seek out opportunities to fall, and will progress all the way down, seemingly with a mind of its own. After considering what the mind of a steel chain might be like, you may want to augment its efforts with some judicious jiggling (of the chain). Once the chain has completed its journey, tie the pull string to the chain, or use the chain itself as a pull string to complete the positioning of the cable.
Round pipes, square hole
Flexible Drill Bit
These things are really slick. The bit is several feet long with a flexible shaft. After cutting the wallboard for the outlet opening, install an old-work mounting ring to protect the wall while you drill.
Old-work mounting ring
To drill down to the basement, place the drill bit (attached to a drill) through the hole and bend it down until it makes contact with the sole plate. Using a heavy work glove to support the shaft while it’s bent, drill the hole through the sole plate and the floor.
If you have trouble getting the bit into position to drill through the plate, try this: Drill a hole through a tennis ball, then slide the ball along the shaft of the bit until it is near the business end of the bit. This will help keep the bit out of the wallboard and guide the bit to the position for drilling.
After penetrating the floor, leave the drill bit in place. Working from the basement, attach the cable to the eye hole at the end of the drill bit. Go back upstairs and pull the drill bit and the cable up through the outlet opening. The cable has now been positioned and can be terminated as necessary.
Flexible drill bit
Getting your cables hidden within walls is a lot of work, but it pays off in a clean, professional installation. This type of work is usually left for professionals because of the special tools and experience required.
This article only covers the positioning of the cable within the cable pathway. Terminations and connections will still have to be made on the way to a complete installation. How-to blogs for all of that and more can be found in our Cable Academy.
Remember to comply with your cable’s minimum bend radius and maximum pulling tension specifications. Make sure that your cable’s jacket is correct for your structure’s fire safety requirements. Checking with your local inspection authority about any special code requirements is always a good idea. And please be careful on the ladder.
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