Repairing a fireplace hearth may become a necessity for several reasons. The fireplace may not work, or the house may become overly drafty. Maybe you no longer use the fireplace, or it has become an eyesore due to neglect or abuse. Often when you purchase an old home, you find the ancient fireplace hearth doesn’t measure up to your aesthetic needs and can therefore use a facelift.
Step 1 – Remove Broken Pieces
Using a chisel and hammer, masonry chisel and grout saw with a razor knife, remove the old hearthstone, any broken tiles and all the mortar beneath it. Keep the concrete and firebox floor untouched for now.
Remove the hearth flooring by either chipping away at the slab or, if stones are mortared together, remove the grout first before placing pry bars under the edge to dislodge and remove. Place the broken stone and debris in a wheelbarrow to transport and dispose of properly.
Step 2 – Clean Away Dust
Don safety goggles and wear a breathing mask when you remove the old hearth flooring. You do not want to breathe in any old fire residue or stone dust. Both can be extremely harmful if you inhale them.
Use a vacuum to remove all dust and debris. Wipe the area down with a damp cloth or mop to remove any leftover dust.
Step 3 – Prepare Wood Length
Use a piece of two-by-four lumber that is one foot longer than the hearth and at least 3/8 inch wider than the depth of the new hearth floor. Cut notches in one side of the board.
Step 4 - Pour New Hearth Stone
Build a form with two-by-fours in which to pour the concrete. You need to first wet down the entire area and then slowly pour concrete into it. Use the notched board, leveling the mixture by pulling it across the hearth. Make sure to move the board side to side quickly while also pulling it.
If you are replacing tiles instead, set the stone in whatever design you wish to choose, making sure to install spacers between the stones. Try to match the grout with the original used on the fireplace exterior.
Step 5 – Smooth the Concrete
Use a trowel to smooth the concrete. Add or remove some to gain a level surface that matches the existing hearthstone area. Move the notched trowel in circular, sweeping motions. Apply even pressure while you smooth the concrete.
Once the concrete starts to dry, remove the two-by-fours. Or if you're replacing with stone tile, remove the spacers. Apply grout liberally; make sure all spacer holes are full to the level at the top of each stone tile. With a damp cloth, wipe away any excess grout before hardening begins.
Step 6 – Allow Adequate Drying Time
Allow the new fireplace hearth to dry overnight.
You may need to use a good concrete and grout cleaner to remove stray stains.