Friday, May 1, 2009

How to Fish Wires Through a Wall or Ceiling

Today were going to talk about how to fish wires through a wall or ceiling. If you have never done this before, it can be extremely irritating. If you need to snake wires often, it'll help to visit a new construction site, which will help you visualize what's behind the drywall and what problems you might run into. Throughout this article I'll show you some diagrams and pictures to better visualize what we are talking about, as well as give some key pointers to help you along the way.

To start off, here are some Quick Tips:

- 99% of the time, the roof line will run the opposite direction as the rafters
- Load bearing walls are more apt to have cats (wood braces) inside them that will prevent snaking a wall
- Outside walls will have insulation inside them
- For easier wire fishing, use the MagnePull

Now to the tools. There are some basic tools and materials you'll need for fishing wires. The first and most important is a FISH TAPE. Depending on the application, you'll want the tape to be 1/8" and around 50-100ft.

Some other items you'll need:

- Electrical Tape
- Flashlight
- Drill
- Wood spade bits
- Wire Staples
- Hammer
- Drywall Keyhole Saw
- Lineman's Pliers
- Wire Strippers

Note: You may not need everything listed here, this is just for general reference. It really depends on where you''ll be snaking the wire and what type of materials are involved.

So lets get started.

For this example, lets say your going to add a center light in a room where there is no light, but there is a switch that controls a receptacle. I'm going to assume we have an accessible attic above the room we are adding the light in.

These next two photos will help you get a better understanding for what your doing.

(Note: Before doing this next step, make sure you have turned off any electricity to this circuit. The fish tape is metal and can easily become energized by touching a wire or the switch).
First thing we need to do is open the switch and pull it out. When the switch is pulled out, you'll want to see if you need to push a knockout out in the back of the box on top. The idea here is you are going to go in the attic and drill into the plate above the switch so you can snake a wire down.

Before you go to the attic, you need to find a way you can find the top of the plate. If there are any A/C vents in the ceiling, that is the easiest way to get some measurements. If not, then look for something that goes through the ceiling that you can use as a reference point. If you can't find any way to locate the plate where you need to drill, a last resort is to stick a long thin screwdriver through the ceiling, directly above the switch. When you have your location in the attic and have found the top of the plate, you will need to drill a hole. I recommend a decent size hole. A 3/4" or 1" drill bit should do the trick.

Drill in the center of the plate and drill straight down. If your doing this with a friend, your ready to snake the wire.

Have your friend shine a light into the light box. Then from the attic you will be able to look down and see the hole you drilled. Now its just a matter of sending the snake down and guiding it through that hole. Once you do, your friend can tie the wire onto the snake and you can pull it up. When you have the wire in the attic, it should be an easy matter to run it over the the location you need.

If you are by yourself, here's a tip:

- Drill another hole next to the one you just drilled. It can be smaller, like 1/2". This will be a hole to shine your flashlight down.

So if you don't have anyone to help, shine your flashlight down the second hole and guide the snake through the hole in the switch box. You will have to then go down and attach the wire. It's important that you make a smooth nose on the snake since you will not want it to get hung up when pulling it from the attic. This part can go much smoother if you can get a helper for a few minutes. When using the steel fish tape to pull the wire from point to point, you may be tempted sometimes to just tape the wire on. DON'T DO IT!


- Do it right the first time

Sounds like a no brainer, right? A lot of people will be tempted to save time by cutting corners at this step. Imagine the frustration when your pulling the wire through successfully, only to have the fish tape half way through your pull. Attach it correctly. Below is an illustration of how this is done.

One last precaution to take is to tape the end of the fish tape and the wire your pulling with electrical tape. This will insure it doesn't get snagged on anything or come loose. Below is the illustration of how this is done.

What if there's no attic space above the area your working in? Your screwed.

Not really, but it does require more work. You will need to notch some drywall and know which way the studs or ceiling rafters are running. If the direction you need to go runs parallel to the beams, you'll be able to snake a wire in that direction very easily. If the beams are running in the opposite direction, this requires even more work. You'll need to cross the beams. The best way to do this is cut a strip of drywall out that is about 4" wide and the length you need to get to. After that, you can drill a hole in each stud and run the wire through the studs or ceiling joists. The illustration below shows what this should look like.

There may be times when cutting back and patching a big section of ceiling just isn't practical, such as an old plaster ceiling. Another option then, would be to make small notches and pass wire through each hole to pass around the stud. If you do this, you should also notch the beam so the wire is recessed or get metal plates to protect the wire. If the beam is notched, it must not be cut to deep as to affect the structures strength. The below illustration shows what this notching should look like.

In some cases you may have to notch around the studs or joists. The ceiling or wall would look like the illustration below.

If your not comfortable with one of these alternative, you can always run the wires along the wall and cover them with a Surface Raceway. They come in different sizes and are paintable to match whatever color wall you might have.

We hope this article was helpful and your wire fishing goes smoothly.

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Related Posts:
MagnePull - Use the Power of Magnets to Help Fish Wires

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