FIREBOX JOINTS

​In many cases the firebox in a fireplace can start to show signs of wear with either missing or loose mortar joints or by completely missing brick. This type of damage is usually caused by water leaching into the chimney from the exterior. 

The joints can be either missing or sometimes dry rotted in which they simply turn to powder. Either way it makes the fireplace unsafe to use.

The firebox joints much like the exterior joints can be tuck pointed. The thing to remember though is the mortar between these joints is not actually mortar but fireclay. Fireclay has a much higher heat value than mortar.

Regular mortar if used will fail and fall out, where clay will hold much longer. If you want to repair the joint just do the following.

1. With a screw driver or pointed tool scrape out all the loose joint material.
2. With a shop vac, suck all the loose debris and dust from the joint.
3. You can purchase fireplace mortar in a silicone type tube from your local home supply store or even find it here.
4. Load the tube into a standard silicone gun and carefully squeeze the mortar into the joint and smooth it off.