Chimney Maintenance 101: Repointing Chimney Mortar

If you have a masonry chimney in your house, the exposed portion of the chimney can suffer water damage. You will observe this water damage as the mortar in your chimney degrades. Left unchecked, your mortar can erode to the point that the brick or stone components of your chimney begin to separate and fall apart. Whenever you observe mortar erosion, you should repoint the mortar in your chimney. 

What Does Mortar Damage Look Like?

Your chimney mortar should extend nearly to the surface of the masonry components of the chimney. It should have a smooth, rounded, concave look to it, so that any water that enters the joint will run out. As your mortar erodes, it will recede from the surface of your chimney and take on a rough, pitted look. When you first observe mortar damage, it is time to repoint. 


Before you start your repair, you will need to gather the right tools, which include the following:

  • a joint raker
  • mortar repair caulk
  • a narrow, stiff-bristle brush
  • a paint brush
  • a joint raker
  • a piece of plastic sheeting

You will then follow these steps to complete the repair. 

1. Remove damaged mortar with your joint raker. Position the wheels of the raker so that they are on either side of a joint. The point of the raker should extend down into the joint. Apply pressure to the handle as you move the raker back and forth across the joint to scrape out the damaged mortar. 

2. With a stiff-bristle brush, sweep out any loose debris left in the joint.

3. Follow up with a paintbrush to remove fine dust from the joint. 

4. Cut the end off of your tube of caulking and insert it into a caulking gun. 

5. Applying gentle pressure on the caulking gun handle, inject a steady stream of caulking into the joint. Ensure that the caulk extends right up to the surface of the joint. 

6. Place a piece of plastic sheeting over the repointed section of chimney for 72 hours in order to give the caulk plenty of time to dry. 

You will notice that after this repair your joints will no longer have a concave shape. As long as you have a smooth bead of caulk that extends right up to the surface of the masonry of your chimney, you should not have to worry about water collecting in the joints. On the other hand, if you have any questions about your ability to make quality repairs to your chimney, you can call in masonry professionals, such as those from Excel Chimney & Fireplace Service, to make the repair for you.