How To Repair a Broken Brick Chimney

Bricks are long lasting materials, but when exposed to the daily wear and tear of the environment up on the roof, they can begin to degrade. Sometimes it isn’t the brick that is the problem, but the mortar instead. A crumbling chimney is a safety hazard and an eyesore! Thankfully you can do something about it with these quick tips.

Step #1: Remove the old mortar. You’ll need to remove all of the old mortar that is part of your broken brick chimney. This generally means taking a chisel to the mortar. Do three or four horizontal rows of brick and then chisel out the vertical rows of mortar. A saw can be used for this process, but up on the roof, hand tools are generally safer.

Step #2: Remove any old, broken, or rotten bricks. If you have bricks that need to be replaced, then remove them as you remove the old mortar. Pull them out if you can instead of letting them fall down the chimney.

Step #3: Scrape the bricks clean. Now you’re ready to prepare the old brick chimney for new mortar. If your chimney is fairly old, you’ll want to pick up some lime mortar instead of the basic concrete mortar that exists today. For bricks that are spaced less than half an inch apart, you’ll need to scrap to a three-quarter inch depth. If the bricks are wider apart, you’ll need to go deeper into the old mortar.

Step #4: Brush it clean. The goal is to remove all of the old dirt, mortar, and debris that are remaining with your chimney. Once it has been brushed clean, you’re ready to wet down the chimney so that it becomes receptive to the new mortar and any new bricks you may need to install. Get the chimney dripping wet and then you’re done for the day.

Step #5: Mist the chimney down again. When you get back up on the roof the next day, you’ll want to get your chimney damp, but not dripping. Mix your mortar up according to its instructions and then allow it to sit for about 10-15 minutes. You’ll see some water puddles begin to form on the surface. Mix it again at this point and then your mortar will last you all day.

Step #6: Repair missing bricks. If you had to pull broken or rotted bricks, now is the time to put them back in. Place a layer of grout on the bottom of the brick to create a seam. Slide the new brick in place and then put mortar in around each joint, the horizontal joints first. Repeat until all of the bricks have been replaced. You may need to cut bricks to size with a compatible brick saw.

Step #7: Fill in the joints. Starting from the bottom, begin packing mortar into the joints that you scraped clean the day before. Do 3 or for horizontal rows and then do the vertical rows. Compact the mortar down, smooth it out, and when the entire chimney has been completed you’ll need to brush the bricks clean.

Step #8: Cover and you’re done! Cover up your chimney with a tarp. It needs to sit 3 days to properly cure. You’ll need to wet the bricks down once per day with a light mist. That’s how you fix an old broken brick chimney!