Basement foundation: cold joint, rock pocket, other?

Good morning - we were putting back insulation and noticed an odd line on the foundation wall in a few areas of the unfinished portion of the basement. Much of that part of the basement is covered by Roxul and pink fibreglass insulation so there may be others. But we noticed these lines in 3-4 areas and are unsure what they are or if they are cause for concern. Reading through the forum and other websites, it looks as though it could be a cold joint, honeycombing, rock pockets or a mix. You can see stones in a few parts but it does go to almost unnoticeable at the ends. We have Delta-MS on the exterior of the foundation. We have also had some record setting rains and no signs of water intrusion from these spots. I’m at a loss and would love some insight. All lines are close to the basement floor slab itself (max. 2 feet off the slab). I’ve attached some photos below of the lines. There’s one about 3’ long on a 15-degree angle (first set of photos), some close ups and a few of the other areas. There is also one photo of a corner where you can see some larger stones. This home is is about 2-2.5 years old and I believe the foundation was poured in the summer (we are recent buyers). Thank you for your time and expertise. It’s weighing pretty heavily on me because all I can think about is this is a structural issue.

They look like cold joints, to me. :smile:

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Yep - cold joints…

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Thanks, Jeffrey. Given the location and look, are we in for issues and is there anything we can really do?

Thanks, Larry. Given the appearance and location, are these something we need to be extremely worried about?

There are no real structural implications, however, these joints are notorious for allowing moisture through the wall. Without knowing the quality of the waterproofing at the exterior of the wall, there’s no real way to predict the potential for future problems.



Are cold joints in concrete bad?

They are usually linear, closely joined and bonded. However, there is a danger of small voids in areas where the concrete is not fully compacted, as with any concrete pour. Generally, cold joints are not a problem structurally if the joint is in compression.

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Thanks again. Really appreciate the insight. Below is a photo of the exterior waterproofing. The red box is where the one 3’ cold joint is that I shared. Would you recommend patching on the interior given we have that exterior protection? And is this fairly common for residential pours?

Tyler as the soil compacts sometimes it will pull that membrane away from the foundation at the top which can allow water to get behind it and find it’s way to small cracks in the foundation. It is good practice to maintain a water tight seal at the top of that membrane through regular routine maintenance.

Thanks, James. Very helpful and definitely something we’ll address in the spring. From your perspective, are these cold joints a cause for concern and should we be patching internally as well even if we haven’t seen any water intrusion? And are these cold joints common in residential pours? Again, thanks for your time and insight.

My opinion from Ohio is that it was just sloppy work and will most likely not be a structural problem.

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The option to “patch” the cold joint would be for ascetic purposes only and if it’s done, it should be AFTER the walls are back filled.