Renovation & Design

How to re-point your chimney

Postmedia/If the mortar lines between bricks on a chimney deteriorate, they will allow in moisture. This can freeze during winter and cause damage to the chimney.

There are a few key things homeowners need to think about when preparing to repair their brick or cinder-block chimneys.

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

The change in how we use fireplaces is also affecting how they age.

Let's deal with a home that has a brick or cinder-block chimney. You will notice a line between the bricks or cinder-blocks; this is the mortar line. Brick mortar lines can deteriorate over time as they are exposed to the elements. If the mortar lines deteriorate, they will allow in moisture. This can freeze during winter and cause further damage to the chimney.

The repair for this is called repointing. Before repointing the exterior of 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 an all-purpose cleaner. This will give you a clean surface to work with. Any dirt, algae or other residue can interfere with the bonding process.

Purchase a multi-purpose adhesive such as Weldbond or a pre-mixed 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 will act as a bonding agent for the new mortar to adhere to.

Once you've properly prepared the surface, get a bag of mortar mix or mortar pre-mixed cement. You have already added the adhesive where the loose material was scraped away. There is no need to add any more adhesive to the mortar mix, but, if you wish, you can add a 1/2 cup (125 mL) of adhesive to two 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 inch (9.5 mm) and the other side is 1/2 inch (1.2 mm). 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 the repairs, wait a month to seal the surface. Seal using a spray bottle filled with an acrylic concrete sealer. Start sealing the brick/cinder block and mortar surfaces at the bottom, working your way to the top of the chimney.

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-- Postmedia News



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