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CMU exterior wall - building code requirement

T

TDarch

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Joined
Aug 30, 2024
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10
Location
California
Hi everyone, I'm working on an existing project with CMU block on the exterior. There is recently a leak through the building, and it is claimed that due to the fact the CMU walls does not have water repellent application on them. The project is in CA and I have been researching CBC to great length and yet to find any code requirement for the CMU wall to be coated.
CBC Section 1403.2 Exception actually says that "A weather-resistant exterior wall envelope shall not be required over concrete or masonry walls designed in accordance with Chapters 19 and 21, respectively."
Please share your knowledge in this matter, as it is surprising to me that the code would knowingly exclude the weather resistant finish on CMU if it is apparently can absorb significant amount of water.
Thanks in advance for your help.
 
Last edited by a moderator:
Who claims the leakage is caused by a lack of a water repellent coating? What is the basis for the claim? Are they alleging that the lack of a water repellent coating is a code violation, or are they just claiming it's a problem because ... [reasons]?
 
Can you provide details? Is the wall cracked? Is there an irrigation sprinkler directed at the wall? Is the wall solid grouted?
 
We had two building where the water "leaked" through the blocks
The first had a lawn sprinkler system causing the saturation of the wall.
The second building had holes in the bonding mason/grout big enough to stick a pencil in some of them. During a driving rain the water ran across the steel beams to the center of the building and dripped onto the ceiling assuming it was a roof leak on a brand new building.
 
I had a project years ago in Southern CA where rainwater seeped through the existing grout joint between the concrete podium and the CMU exterior wall. It was a cold joint, and there was no other dam. It was asking for trouble.

We called the local ProSoCo rep and asked them to visit the site and recommend a post-construction coating for the CMU and for the podium deck, especially at the grout joint. Their suggested coating worked like a charm. I don't remember the name of the specific coating, but I do recommend you call them and ask.
 
TDarch said:
it is surprising to me that the code would knowingly exclude the weather resistant finish on CMU if it is apparently can absorb significant amount of water.
Thanks in advance for your help.
Click to expand...
It’s not that the cmu can absorb water, it’s that the water does not harm the cmu like it would cause a wood framed wall to deteriorate.
 
ICE said:
Can you provide details? Is the wall cracked? Is there an irrigation sprinkler directed at the wall? Is the wall solid grouted?
Click to expand...
Yes the wall is solidly grouted. No crack is big enough for the naked eye from 3 feet away, but I don't know about hair line at the joints.
 
Yankee Chronicler said:
Who claims the leakage is caused by a lack of a water repellent coating? What is the basis for the claim? Are they alleging that the lack of a water repellent coating is a code violation, or are they just claiming it's a problem because ... [reasons]?
Click to expand...
a Rilem tube test was performed and there was high water absorption rate. But I have done some research on this test it is is not recommended for accessing the water absorption of masonry wall.
 
Joe.B said:
As in this:
View attachment 15425

Or this:
View attachment 15426
Click to expand...
I can't see the link for some reason. Could you please check.
Yankee Chronicler said:
Who claims the leakage is caused by a lack of a water repellent coating? What is the basis for the claim? Are they alleging that the lack of a water repellent coating is a code violation, or are they just claiming it's a problem because ... [reasons]?
Click to expand...
I think the claim is an oversight by the architect. I have yet found any code violation in related to this.
 
Joe.B said:
Is the CMU block wall completely above grade, or is a portion of it below?
Click to expand...
it is completely above grade and grouted.
Yikes said:
I had a project years ago in Southern CA where rainwater seeped through the existing grout joint between the concrete podium and the CMU exterior wall. It was a cold joint, and there was no other dam. It was asking for trouble.

We called the local ProSoCo rep and asked them to visit the site and recommend a post-construction coating for the CMU and for the podium deck, especially at the grout joint. Their suggested coating worked like a charm. I don't remember the name of the specific coating, but I do recommend you call them and ask.
Click to expand...
yes, I would think the wall can get damn but not to the level of wetness. I got some recommendation for the water repellent companies, will call and check. Thanks
 
TDarch said:
a Rilem tube test was performed and there was high water absorption rate. But I have done some research on this test it is is not recommended for accessing the water absorption of masonry wall.
Click to expand...

Your opening post said there was a "leak through" the building. Normal absorption of water by an exterior CMU wall is not a "leak." It's a normal phenomenon.
 
Yankee Chronicler said:
Your opening post said there was a "leak through" the building. Normal absorption of water by an exterior CMU wall is not a "leak." It's a normal phenomenon.
Click to expand...
sorry my bad, the claim was that since the water absorption through the test is so high the water will eventually seep through the CMU.
ICE said:
What activity is going on in the building? Is there ventilation?
Click to expand...
yes there is ventilation. It's a gym with enclosed parking on ground floor.
 
TDarch said:
it is completely above grade and grouted.
Click to expand...
It sounds like there is more of a concern than there is an issue. With it being completely above grade, I don't think you're going to find a code violation. Keep in mind though that the codes are a bare minimum, and they're really focused on life-safety. Best-practice design should take much more into account and I know it's common to call out a waterproof coating for concrete/CMU walls.

Run a google search on "concrete waterproofing sealer".
 
Context is required. If this building is located where you are, the climate is mostly dry and close to the ocean. Did the moisture appear unexpectedly during a wet spell? Where was the H2O prior to showing up on the inside of the building? Has this happened in the past or only recently? When was the building erected?
 
Plain old gray concrete block is as water repellent as a sponge. It should at least be painted, even if the code doesn't require it. Thoroseal (or whatever it's called since somebody bought them out) would be even better.
 
TDarch said:
sorry my bad, the claim was that since the water absorption through the test is so high the water will eventually seep through the CMU.
Click to expand...

That would suggest that water is not currently seeping through, which in turn suggests that water may never seep through.
 
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