What is Chimney Mortar?

Mary McMahon
Mary McMahon

Chimney mortar is a type of mortar which is designed to be used in chimneys. The process of applying mortar to a new chimney is known as pointing, while repairs are known as repointing. A related process, tuckpointing, involves the use of two contrasting colors of mortar to create the illusion of a very fine joint. Many hardware stores sell chimney mortar and can order specialty products by request.

Chimney mortar must be resistant to heat.
Chimney mortar must be resistant to heat.

Like other types of mortar, chimney mortar is an adhesive product which is designed to hold pieces of masonry such as bricks or rocks together. In addition to acting as an adhesive, chimney mortar must also be somewhat heat resistant so that it will not be damaged by high temperatures in the chimney. The mortar keeps the chimney stable and prevents water from penetrating into the chimney and the surrounding structure. Chimney mortar is sold as a dry powder which must be mixed by the user when it is needed.

Repointing is often regularly recommended for brick and stone chimneys. If mortar is allowed to decay, it can destablize the chimney, potentially creating a dangerous situation. As mortar cracks and breaks down, it also admits water, which can create water damage, promote the growth of mold, and allow bricks to crack from stress. Chimneys should be regularly inspected from top to bottom for signs of damage to the mortar, and repointed promptly when damage is identified.

If caught early, damage to chimney mortar can be repaired by a homeowner, working in an day or weekend to carefully remove old mortar section by section and replace it with freshly mixed chimney mortar. It is best to do this when the chimney will not be used in the near future, allowing the mortar plenty of time to cure. Ideally, a month should go by, although specific products may have more particular recommendations.

If mortar is badly damaged, bricks are cracked or missing, or the chimney appears to be listing or sagging, it is not safe to perform repointing as a do it yourself project. A professional should be brought in to determine whether or not the chimney can or should be salvaged, and to do the work. It may be necessary to demolish and rebuild the chimney if it is badly damaged. People who attempt to fix unstable chimneys themselves could be at risk of causing a chimney collapse, which could cause severe injuries and/or property damage.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


Having just finished some repointing on my chimney, I'd like to share a couple of tips with anyone attempting this job themselves.

Firstly, make sure you mix the chimney mortar according to the directions. It's really important to get it to the correct consistency to make it work properly.

Very hot or dry climates may make the mortar dry out too quickly, so keep a water spray bottle handy to avoid this.

The last thing, which in many ways is the most important, relates to the conditions you find once up there. If you are removing quite a lot of the old mortar it may be better to abandon the job and go for a complete rebuild. This will at least mean the chimney is secure for several years to come.


If you want to try repairing chimney mortar yourself, but are a little inexperienced, you'll find plenty of step by step instructions on the Internet. That's what I did, having checked it was stable of course.

Safety harnesses or even scaffolding may be needed if your chimney is not easy to get to. In that case I'd call a professional to do the job for you.


Even though it seems old fashioned, it's actually not a bad idea to have a fireplace and use it for heating now.

People think it must be very polluting, but in fact wood smoke isn't bad compared with some of the ways electricity is generated. It is coal smoke that is the real culprit when it comes to bad pollution.

And, in theory, wood can be a renewable fuel, and can encourage people to plant trees which is always a good thing.

So sure, though it can be a pain to maintain your chimney mortar, I think it's really worth it, especially if you are building a new home and can control what kind of mortar is used to begin with. A real, old fashioned fireplace and chimney could work out nicely.


You really do have to make sure you check your chimney regularly to make sure it is up to scratch. The other night we heard a loud noise which sounded like a gun shot or something. When we investigated, it turned out that the neighbor's chimney had partly fallen in the wind.

Luckily no one was hurt, although that could have been a possibility. And they did have some damage to their roof as well, so it's going to be even more expensive to fix.

It certainly prompted me to go up and have a look at our own chimney, which thankfully, still looks like it is in good repair.

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