How To Repair Fireplace Mortar

What You'll Need
Wire Brush
Protective Eyewear
Air Mask

Damaged or cracked fireplace mortar can be extremely dangerous and should be repaired immediately. Damage to the mortar holding bricks and masonry in place can allow cinders and sparks to find their way between the mortar and into flammable floorboards and walls.

In order to avoid home fires resulting from damage to the chimney or fireplace, regularly inspecting the mortar in a fireplace is recommended, particularly for an older chimney and fireplace or for one that has been subjected to building settling, earthquakes or other events that might result in damage. Mortar can also crack as a result of weather changes as the bricks expand and contract with cold weather and freezing.

When inspecting the fireplace, check both the inside of the fire box and the outside chimney. Look for places where the mortar is cracked, broken or has fallen out of place. Conduct an inspection several times a year and after any major event that might result in damage to the chimney or fireplace box. Fireplaces and chimneys with extreme cracking and damage to the mortar and masonry may need to be replaced entirely. However, with regular inspections and repairs, masonry can remain in good condition for many, many years.

Maintaining fireplace mortar is an economical and inexpensive method of taking care of the chimney, fireplace box and surrounding area without resorting to unnecessarily replacing the entire structure.

Step 1 – Remove Debris and Damaged Mortar

Wearing protective eyewear and a face mask to protect from dust and debris, use a wire brush to brush away broken and damaged mortar. This will remove any debris and prepare the surface of the existing mortar for repair. Removing debris will also allow for closer inspection of all of the masonry and mortar joints in the fireplace and chimney structure.

Step 2 – Prepare New Mortar

Prepare the mortar with water following the directions on the package. Be sure you have purchased and are using mortar that is specifically designed for use in fireplaces or high heat applications.

Step 3 – Use Trowel for Mortar

Using a masonry trowel, place a small amount of mortar on the trowel. Trowels come in different sizes and shapes, so choose one that fits well into your hand and is easy for you to move around as you place the mortar between the brick joints.

Step 4 – Place Mortar on Masonry

Place the mortar into the cracks or damaged area between the bricks. Push the loaded trowel across the area and push the mortar into the cracks and fill it completely. Repeat this as needed until the cracks are entirely filled with new mortar.

Step 5 – Remove Excess Mortar/Smooth Mortar Surface

Use a damp cloth and remove any excess mortar. Smooth the surface of the repair with your hands and push the mortar more deeply into the cracks.

Step 6 – Allow for Drying

Allow the mortar to dry completely for 24 to 48 hours.

Step 7 – Clean Up Debris

Clean away any remaining debris from the mortar with a paintbrush.