You stand in your yard, coffee or beer in hand, and look up at your chimney. You can clearly see that there is loose mortar between the bricks, or that even some of the mortar joints have fallen out, and suddenly dollar signs are flashing in front of your eyes. You want to know what the correct repair would be, what your possible options are, and gulp, what is this gonna cost?
Bear with me, watch the video of the author below, then continue reading the rest of this informative article. I promise that you will feel substantially wised-up after you get through this. But first, grab a cup of coffee (or maybe a beer, or a glass of something…) 10-minute video.
Ok, you get the idea about tuckpointing. If you look at this video still above, you will get an idea of how much mortar I ground out of the worn mortar joints. I dug in about 1 to 1.5 inches. If you look at the original mortar that is still in place, you can see that it is still firm and in good condition; that is the way is should be. When you tuckpoint a chimney, there needs to be a good, solid base of hard mortar to “tuck” the new mortar up against. In other words, it does no good to tuckpoint a chimney if the mortar is soft and loose all the way across the width of the brick. Bricks are about 3-4 inches wide. If you can take out more than half of width of the brick’s mortar bed (when laying a brick, you cover it with a “bed” of mortar), then it’s time to rebuild the chimney.
For what it’s worth, years ago I went out to give an estimate on a chimney that was very old. I took a screwdriver to the mortar joints and poked all the way through the joints- the mortar came out easily as if it were sand. I got up on the roof and gently pushed on the chimney, and it moved substantially. I told the homeowner that the chimney needed to be rebuilt, and showed him why.
Rebuilding the chimney was not in his budget. He asked for the bid to tuckpoint it and signed off on it, reasoning that tuckpointing would be better than nothing. Tuckpointing has the effect of installing a grid work of wedges. We did the job and came back a month later to see what effect the tuckpointing had on the chimney. I got up on the roof and pushed against the chimney, AND IT DID NOT MOVE! So that’s some information to chew on…
In the above photo, the top 8 courses (layers) of brick need to be rebuilt. The mortar joints below the metal band are in good enough shape that they can be ground out and tuckpointed and this combination of repairs is quite common. Many older chimneys were built up with the brick and parged (coated with mortar) on the inside with mortar:
As the building codes improved, terra cotta flu lining was incorporated into chimney construction as an added layer of safety. It seems that this code came in during the 1940s. We have repaired several chimneys that had a perfectly good terra cotta flu lining intact, yet the brick and mortar joints had deteriorated. This happens due to exposure to the elements, freeze-thaw cycles year after year and chemical reaction from oil furnace soot getting wet and dissolving the mortar joints from within. Rarely do you see any oil furnaces in homes at this date; however, they were a huge part of the market for many decades in Oregon.
Another factor for chimney damage in our climate is moss. It can grow into mortar joints and break them down. Therefore, you want to keep the moss removed from your chimney. A good wire brush with a scraping blade at one end does wonders!
Our policy on repair work is that we waterproof all of our work to prevent freeze damage. The waterproofing agent that we use needs to be re-applied every 9 years (the manufacturer says 10.) The waterproofing dries clear.