How do I Attach a Mantle to a Completed Fireplace?

Measure the fireplace surround to determine a depth and length for your mantle. To determine the vertical placement of the mantle, allow 1 inch of space between the hearth and the bottom of the mantle for every 1/8 inch the mantle sticks out from the wall. If a mantle extends 8 inches from the wall, for example, your mantle height should be 64 inches from the hearth.

Research your local building codes to see if any special requirements apply.

Paint or stain the mantle, if necessary.

Position the mantle against the wall, making sure it is centered over the fireplace and level. Mark this placement on the wall with a pencil.

Measure the length of the back of the mantle. Subtract 2 inches from this measurement.

Cut the 3/4-inch piece of lumber to the length you calculated in Step 5. Make a French cleat by setting your table saw at a 45-degree angle and sawing the lumber in half horizontally.

Screw the piece of lumber that has the chisel point facing down to the back of the mantle using wood screws, making certain it is secure and level. Position the mantle against the wall, and mark the position for the other half of the cleat. Make certain that the mantle rests on the floor or hearth.

Screw the piece of lumber with that has the chisel point facing up to the wall using concrete screws. Check to ensure it is level.

Drop the mantle over the French cleat, making certain it is centered over the fireplace.