Chimney Repointing

June 21st 2013
Chimney Repointing

Chimneys are being converting to metal insulated type of chimneys rather than the old flue-liner type with solid brick /block chimney chases. The reason for this change is the devices being used in the chimneys are also changing. I am seeing less traditional wood burning fireplaces and more controlled burning appliances being used in fireplaces such as heatilators, wood pellet fireplaces or natural gas or propane fireplaces which require a different type of chimney insert to properly exhaust gases created when fuel is burned. The change in how we use fireplaces is also affecting how they age over time.


Let’s deal with a home that has a brick or cinderblock chimney. You will notice a line between the bricks or cinderblocks; this is called the mortar line.


Brick motor lines can deteriorate over time as they are exposed to the elements. If the mortar lines deteriorate it will allow moisture into the chimney. This moisture which can freeze is some areas during the winter and cause further damage to your chimney. What do you do? The repair for this issue is called repointing.


Before repointing your chimney you must first make an effort to remove as much of the loose mortar as possible using a small pointed trowel. Once you have removed the loose mortar, wash the mortar lines with a good all purpose cleaner such my home cleaning formula. This will give you a clean surface to work with. Any dirt, algae or other residue can interfere with the bonding process.


Purchase an multi-purpose adhesive such as Weldbond or a premixed concrete adhesive. Brush the adhesive into the mortar lines you are going to repoint, meaning where you are going to put new mortar to replace the old mortar you have scraped out. The adhesive is going act as a bonding agent for the new mortar to adhere to. Once you’re properly prepared the surface you need to go out and get yourself a bag of mortar mix or mortar premixed cement.


You have already added the adhesive where the loose material was scraped away. There is no requirement to add any more adhesive to the mortar mix. If you feel better having adhesive in the mortar mix as well you can add more of the adhesive to the mortar mix prior to mixing. Add a 1/2 cup of adhesive to a 2 shovels of mortar mix. The consistency should be such that when you grab a handful of this mix you are able to squeeze it and it will come out between your fingers.


Now you’re ready to place the mortar. Do not do this in the direct sunlight or heat. You will place the mortar using a pointing tool. This tool looks like a ‘Z’ and has two sides to it: one side is 3/8” in size and the other side is 1/2” in size. Using a piece of plywood put a small quantity of mortar on the plywood and push the mortar off of the plywood using the pointing tool into the grove where the mortar is to go.


Once you’ve done all the repair work, wait a month to seal surface. Seal using a spray bottle filled with an acrylic concrete sealer. Start sealing the brick/cinderblock and mortar surfaces at the bottom working your way to the top of the chimney.