A flat panel TV above your fireplace is very cool until you try and hide the cables. The fireplace prevents running the cables straight down the wall and the stud framing prevents running the cables laterally inside the wall. If your fireplace is on an interior wall, you may be able to go up the wall, however, that doesn't work on exterior walls. The top plate of the wall blocks access to the attic and the roof prevents drilling down from above.
The typical solution is to cut access holes in the walls and run the cables. In our older home, the walls are wood paneling which has been covered in heavy wallpaper and painted. Not an easy thing to repair without obvious blemishes remaining. A second option is to use the mantel to hide the cables and that is the option I chose. To my amazement, this worked very well.
This instructable will show you how to use a board, a hinge and a magnet to run cables down to the floor (left of fireplace). I also discuss alternatives to accomplish the same thing without using a hinge. Hopefully, this will provide you with some good ideas for your home.
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Step 1: How this works
This picture shows how the cables are hidden in the mantel piece. The hinge on the old barn wood opens a door for access to the cables. The cracked and worn nature of the wood makes the door virtually invisible as it appears to be a split in the wood. There are other ways to accomplish the same effect without using a hinge and I'll discuss those options as we go along.
Before you decide to install a TV above your fireplace, it is advisable to place a thermometer above the mantel and make a fire. Monitor the temperature over an hour or so and make sure it does not exceed 90°F. If the temperature remains below 90°F, it is safe to mount a TV above your fireplace. It is also advisable to check your local codes for running cables.
You will also need to use a stud finder and mark the location of the wall studs. The wall stud locations will determine where you will make the wall holes for access. This is especially true for the hole near the edge of the fireplace as this is a common place for a single or double stud. In my case, there were 2 studs to the left of the fireplace which I had to drill through but that wasn't really a problem.