Brick + Beam Detroit

Basement masonry mortar repair. Can/should I do it myself?

Asked by Keegan Mahoney at 7:17am on Jan 29 2016

I'm trying to decide if I should learn to re-point my brick basement walls myself, or if it is a job best left to a mason who works with historic brick. I'd be grateful to hear from anyone with experience either way!

My basement was painted at some point and as the paint flakes off, the mortar behind it has been eroding. YouTube makes it seem like repointing is something I can do, but I also know that historic brick pointing can be botched easily, with serious implications for the integrity of the walls. Stories, resources, and contractor recommendations are appreciated.


at 11:31am on Jan 29 2016

Before going into the question of whether you should do the repointing or hire someone, there are a few factors to consider.

First and foremost, is to identify and treat the underlying cause of the mortar deterioration. This could be caused by the previous painting of the brick, which can trap moisture in the masonry and cause the mortar to fail. It can also be caused by moisture management issues such as basement leaks, poor drainage around the house, any parging (cement coating) on the outside wall/foundation. In addition to the mortar problems, are you also having issues with efflorescence -- the crystalizing of salts on the surface of or within the brick (leading to spalling)? Regardless, identifying and treating the underlying cause of the masonry/mortar problems needs to be done first.

If the paint is the primary problem, the second step is to figure out if can be removed. This is not absolutely necessary, but it will help prolong the life of the new pointing, etc. This can sometimes be done with moderate pressure water cleaning or may require the proper use of a chemical cleaner. This process is going to knock out even more loose mortar and you are going to have to air out/dehumidify the basement and masonry thoroughly before repointing.

Third issue is mortar type to use for repointing. Depending on the age of your house, a very different type of mortar from contemporary cement-based mortar. If your house was built before 1930, it probably has a high lime or all lime content (little or no Portland cement). This type of mortar was designed to be softer (to better absorb stress from building movement) and more breathable (to allow excess moisture out to travel through the mortar rather than the brick.) Ideally, you will have your mortar tested to identify its composition and then use a custom mortar based on that original mix for the repairs. At a minimum, I would use a Type O mortar (which is relatively soft and breathable). Do not use Type N mortar, the most common stuff you will find at Home Depot etc.) or any form of cement.

Finally, repointing can be done DIY with some practice, but it would be good to connect with someone who has experience working on vintage masonry who can show you some firsthand techniques. High lime mortars can be trickier to install. Also, if the mortar is severely eroded, you may need to repoint in lifts (small additions of mortar) for it to cure correctly.

Check out Technical Preservation Briefs 1 & 2 from the National Park Service for more info :

at 7:23pm on Feb 3 2016

Matt's answer is terrific. Sloppy masonry repair lives "forever" and is one of the best ways to mess up the looks of a house. But...... in the basement. Seems like a great place to learn how to tuckpoint.

at 9:37am on Feb 29 2016

Thank you for the responses, particularly your very helpful guidance, Matt. I appreciate it.

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