How to Repair Chimney Cracks

It's important to keep your chimney in good working order. The chimney provides your fireplace uses to exchange combustion gases and fresh air. However, over time and with use, a chimney can become cracked. When this happens it must be repaired. It is important to fix to avoid water damage.

Supplies

• Crown sealer 


• Paintbrush 


• Silicone sealer


• Mortar


• Trowel


• Bucket  

1. Examine the chimney for any cracks. Start at the top and work your way down, checking all of the faces on the chimney.


2. Cracks located on the top around the crown can be sealed with a crown sealer.  Use a brush to apply the sealer, and when dried it will create a waterproof material over the crown surface, which will prevent water from causing further damage.


3. Use a silicone sealer or caulking to seal any small fractures to the mortar within the chimney's bricks.  This will prevent water from seeping in and expanding the cracks during the freezing and thawing cycle. 


4. If the mortar has fallen out of the chimney, mix a batch of new cement per the manufacturer's directions and reapply it to the areas where the damage has occurred.


5. Begin by using your chisel to remove the old mortar. If necessary knock out any loose pieces with a hammer, this should be done before applying the new mixture.


6. Pack the new mortar tightly into the crevice. Use a corner of the trowel to run the mortar into the joints. This will create the concave indentation, which is common on most brick and mortar surfaces.