Foundation basement wall: Cold joint, rock pocket, concern?

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 a structural issue. Looks like I can only post one image as a new user. May have to post another after.

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

1 Like

Thanks Larry. Are these types common in residential pours? And at that area (just off the slab)? We have external waterproofing (photo below) so do we patch internally or just leave as is? Just a bit lost on what to do and if this is a major concern given what we have for waterproofing. Appreciate the time and insight.

Contact a local inspector and have him look at it, on site.

Good luck to you in your project… :smile:

That foundation, overall from the picture looks good. That little small location just did not get hit with the vibrator and lacks the consolidation from a delay between pours, but overall, looks like they did a good job. If that is a fully adhered waterproofing membrane with a dimpled membrane protector, I would not be concerned to much with any water leakage.
As far as the interior, if it is an aesthetic problem, it can be repaired using a product similar to this;

1 Like

Thanks, Marcel. Attached is a photo of the exterior. The red box is where the 3’ cold joint would be. So we should be good from a waterproofing perspective? Interior is framed and insulated (with vapour barrier) so you recommend just putting that all back together? Glad they did a fairly good job. Is what we have fairly common in residential pours? It doesn’t look too bad, but I don’t have anything to benchmark it against. Thanks again!

If the water proofing was done properly like it should be, sealing the interior won’t solve anything. If there is a breach in the water proofing, the water intrusion will occur anywhere on the interior. If you have the product name of the waterproofing system they used, check the installation instructions compared to what was done.
Why was the interior framing taken apart to begin with, just curious.

Looks like it’s been done properly and we haven’t had any issues with water anywhere else. We had about 90mm of rain in 36 hours the other month so it was a good test. A door joint above was leaking (not caulked properly) so during that big storm, had some water enter from the ceiling down so we removed as part of trying to figure out what was happening.

These cold joints - are they common in residential pours? I know you mentioned the foundation looks like they’ve done a good job and if there’s waterproofing we should be fine, so just wondering for my own knowledge why this was overlooked when the forming was removed. Seems like the consensus is that these types of joints aren’t structural - correct?

Thanks again!

These cold joints is something that happens regularly amongst residential foundation contractors, and it is only because of poor scheduling of the concrete trucks or the time it takes for them to reposition the trucks on site or waiting to long to return where they started the pour. It does not contribute to structural issues unless shown to be a lot worse than the pictures you show. A worse scenario would be when complete consolidation with a vibrator is impossible to penetrate the bottom layer because it is hardened to much, that would constitute a real cold joint showing weakness in the wall and allow easy access for water intrusion.

Here is a quote from Construction Magazine;

" By Concrete Construction Staff

What is meant by the common term 'cold joint?"

A cold joint is a plane of weakness in concrete caused by an interruption or delay in the concreting operations. It occurs when the first batch of concrete has begun to set before the next batch is added, so that the two batches do not intermix. Sometimes cold joints occur because of emergency interruptions and delays and sometimes because of the work stoppage at the end of the day, but they can 'also occur from poor consolidation. To prevent cold joints in walls, beams and other structural components it is necessary to place concrete in layers about 18 inches deep and intermix each layer with the previous one by using a vibrator. Placement of concrete should begin in the corners and work toward the center."
Now in residential contractors, you don’t want to look at that 18" to much because that would rarely happen. LOL

1 Like