Mounting a flat screen TV above a fireplace presents certain problems because the mountings can interfere with the chimney, and the heat from the fireplace may damage the TV. On the other hand, a brick fireplace is extremely secure, and can likely support the weight of a flat screen TV quite well. Experts say that most of the time, a flat screen TV can be mounted above a fireplace safely. Before you install it, make sure that your fireplace is suitable. Once you do, you can mount the flat screen in a manner similar to the way you would mount it to any other wall.
Measure the length and width of the fireplace to ensure that your flat screen TV will fit above it. Mark the dimensions with a piece of chalk.
Get a good roaring fire going, then tape a thermometer to the part of the wall where you intend to place the TV. Most flat screen TVs need to operate in a temperature of 37.8 degrees C or less. Compare the specifications of your TV with the temperature of the wall while a fire is going. If it's higher than the TV can handle, you should either find another place for the TV or resolve never to have a fire in the fireplace while the TV is installed. (Most modern homes have a brick facade above the fireplace, which isn't actually part of the chimney. This is good news because it means the temperature from the fireplace won't affect the TV.)
Place the first section of the wall mount in position, corresponding to the chalk marks you made in Step 1. Use a carpenter's level to make sure the mount is parallel to the floor, then mark the locations of the mounting screws on the wall.
Drill holes in the walls using a masonry bit. Drill carefully so you do not inadvertently drill into the chimney,
Insert #8 plastic anchors into the holes you have made. (Some flat screen TV mounts may come with their own anchors for use with stone walls. If you have them, use them instead.)
Place the first half of the TV mount in position. Secure it to the wall using lag screws (or the screws provided with the mount), inserting them into the anchors you have placed. Tighten them into position with a socket wrench, then give the mount a careful tug to see if it is holding.
Lay some cotton towels down on the floor, then lay the flat screen TV face down on top of them. This lets you attach the second half of the mount without scratching the screen.
Position the second part of the mount over the back of the TV and screw it into place with a screwdriver. Give it a soft tug to make sure it is secure.
With the help of a friend, lift the TV into position above the fireplace, fitting the two halves of the wall mount together. Lock the mount in place using the mechanism provided in the mount, then test it to see if it is holding.
Take care not to mount your TV too high above the fireplace. Ideally, a TV should be at about eye level when you sit down to watch it. You can make it a little higher than that if you need to, but if you go too high, you'll have a crick in your neck from watching it.
Take care how you position the TV's cables and wires. You will not be able to slip them behind the wall--meaning they'll need to be run along the facade of the fireplace--and they should be insulated against any heat from the fire just as the TV is. The best option is to run them parallel to the ground, out from either the left or right of the TV, and then directly down to the floor after they have cleared the fireplace. You can use adhesive to hold the wire in place, or a channel made of plastic or metal (available in more home improvement stores). The latter option works well, because you can paint the channel to match the colour of the wall, thus hiding the presence of the wires.