Add a support ledge to the top to keep the tile in the middle over the firebox from sagging before the thin set hardened nail a 1 x 2 board across the top of the opening.
How to lay ceramic tile on a brick fireplace.
Tile all the brick.
Install outlet inside fireplace to accommodate new electric insert.
Nail a straight 1x board horizontally across the fireplace in line with the top of the firebox and use its top edge as a shelf as you set the tiles.
Install thinset cement base directly to the existing brick or apply a cement board substrate.
Set the first tile in the center front of the hearth and place the next tiles evenly around it.
The process phase 1.
Meanwhile measure the fireplace to determine the number of tiles and quantities of thinset and grout that you will need.
Work up from the board first then when the thinset hardens take it off and work down the sides of the fireplace.
Use the flat side and edge of the trowel to smooth the thinset eliminating any ridges or bumps.
Allow the thinset to cure for 24 hours before tiling.
Butter the back of the tile with thinset using the edge of the trowel.
The thinset will cover the bricks and mortar and provide a flat smooth surface for tile installation.
Repeat this process for the other three cut tiles at the base of the legs.
Using a trowel spread an even layer of thinset over the bricks.
The board also prevents the tiles from slipping before the adhesive cures.
Soak a rag in white vinegar and scrub any soot from the face of the fireplace.
Lay out the tile directly on the hearth to help determine the pattern they will be installed in.
Allow the brick to dry for up to two days before proceeding.
Use a wire brush to remove any loose mortar or brick pieces from the brick surface.
Create a box for the electric fireplace to rest on and be screwed into.
Push the tile into place and wiggle it until it holds against the wall evenly spaced between the hearth and the tile above.