The mortar between the stones on my stone foundation is turning to powder…why?

- Thursday, May 12, 2022
A1 Foundation Crack Repair

If you have a stone foundation, you may have seen a white powdery substance on the floor next to the foundation wall.  What is this stuff and what should be done about it?  The Crackman explains.

Narrator: It’s time once again for the “Crack Man Podcast” hosted by A1 Foundation Crack Repair. I’m Darren Kincaid here with the Crack Man himself, Rich Comeras. Rich has 30 years’ experience in the construction industry and over 25 years as the president and founder of A1 Foundation Crack Repair. This podcasts provides expert basement waterproofing, concrete repair, and preventative maintenance tips for homeowners and businesses. A1 Foundation’s valuable insight will help avert a disastrous flood within the basement, health problems associated with water infiltration, and protect your biggest investment….your home. The topic of today’s podcast: The mortar between the stones on my stone foundation is turning to powder, why?

Narrator:  So, Rich, why would the mortar between the stones on a stone foundation start to crumble and turn to powder?

Rich: That’s a great question. Here in New England, we have a lot of stone foundations. And we get calls and we have a home side of our business that just does stone foundation repointing. And first of all, the reason why stone foundations, the mortar in between the stones, deteriorates is because of moisture, age, and freezing and moving of the foundation itself.

We get a lot of calls, may it be in Massachusetts, Rhode Island, Connecticut, New Hampshire with this issue. The people are seeing rodents coming in between the stones, and they see the mortar, that powdery material on the floor, near the wall on the floor; and they clean it up and it comes back. And why the mortar is so important in between the stones is because it’s the glue that holds everything together. And when that decays, one stone will start to go down a little bit, and then the one on top of it goes down a little bit, and then you can have a structural issue.

So, what needs to be done is the mortar needs to be cleaned out in between the stones, and we clean that out with hand tools. Why hand tools? So that we’re not going to disturb the mortar that’s good that could be above it. Whereas if you use a drill bit, a drill bit on a chisel setting will vibrate the stone, and the mortar above that stone will break and then that has to be repointed. Another reason we use the method that we use is we want to keep things intact and we want to take care of what’s broken. Some people want to use a power washer to clean out mortar. While you’re going to take out some good mortar, you’re also going to create a lot of water in the basement. And that basement floor is concrete which will retain water, and then even if you suck it up with a wet vac, that water’s going to evaporate, you’re going to have moisture in the air.

Recently I was able to take a trip to Arizona, to the Grand Canyon, and I ran into something that was very interesting. Based upon this subject that we’re talking about, “Why does mortar on my stone foundation break down”? I went out into the desert on a reservation, and these remains of the structures that the Native Americans have built. Out of red stone, they put stone, and then they made a mortar, and I’m talking over 1,500 years ago. And they made mortar and put more stone on top of that, mortar and stone, and they built these quite elaborate structures. That mortar that was in between the stones over 1,500 years ago was good, and they didn’t repoint it. Why didn’t they have to repoint it? Because they were in a desert, it’s dry, and it remained all these years. Whereas in New England, we have coldness, we have more water, we have freezing, we have dampness, which then causes the mortar to break down, which we want to repair because of rodent infestation, we want to repair it for structural integrity, and we want to repair it so that cold, moist air doesn’t come in and cause more issues.

Narrator: Alright, thanks Rich for explaining why stone foundation mortar will start to crumble and shatter.

Narrator: Alright, well thanks Rich for explaining the case of the mysterious wall crack leak.

Narrator: If you have a basement water problem and think you need a professional, or, if you’d like more information on foundation crack repair and basement waterproofing topics, please visit or call Rich at (866) 929-3171. Or you can email Rich at Thanks for listening and keep that basement dry.

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A-1 Foundation Crack Repair, Inc. is a fully registered home improvement contractor. Contact us today to talk to a knowledgeable, master waterproofing professional.

Toll Free: 866-929-3171

Call Us Today at 866-929-3171

A-1 Foundation Crack Repair, Inc. is a fully registered home improvement contractor. Contact us today to talk to a knowledgeable, master waterproofing professional.