Dark line on poured concrete wall

I am not sure what is causing this line, it is dry and my original thought was that it was from separate pours. If someone could point me in the right direction I would certainly appreciate it.

What’s the other side of the wall look like…

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Clear, the garage is on this wall with a significant slope towards the road.

Is that a brick wall, or is it a poured concrete wall with a brick pattern from the forms? From Here in TN it looks like a poured concrete wall.


The vertical lines in the wall are where the concrete forms were butted together.


Scott nailed it.


To Me that diagonal like sloping down to the right looks like it might be a cold joint , But I’ll defer to a few of our concrete tradesmen who frequent this forum for their opinion.


Thanks Bert, I was thinking the same thing but I will wait for confirmation from a Tradesman.

That’s my bad, I am referring to the horizontal sloping dark line.

Poured concrete w/pattern.

It may not necessarily be a cold joint but a start and end point of the pour?


I would call the sloping line a cold joint.


I’ve poured enough concrete in my career to agree with Randy. Too much time lapse between pours so you end up with a cold joint line. There is typically nothing wrong with that when it is well consolidated when the pour resumes. Since we were not there, we have no idea how much time that was. Using additives like plastisizers would by you some time on delays.

Cold Joints

Cold joints are formed primarily between two batches of concrete where the delivery and placement of the second batch has been delayed and the initial placed and compacted concrete has started to set. The full knitting together of the two batches of concrete under vibration to form a homogeneous mass is therefore not possible, unlike the compaction of two fresh workable batches of concrete. This could be a potential plane of weakness.

Cold joints, unlike cracks that form in hardened concrete through tensile restraint, are not gaps in the concrete but merely seams containing no appreciable void structure. 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. However, the location of the joint within the structure, the structural function of the element and aesthetics need to be considered when assessing a cold joint.



WOW great information Marcel! Thank you for chiming in everybody, I appreciate all of the help!

Guess I am late to the party. 3rd 14 hour day in a row. Tis the busy season for concrete afterall…

That’s exactly what it is Bert. Aluminum forms with a silicone rubber mold/liner to create a brick pattern.

Yep, they also increase workability time.

If the “older” mud is still workable and not fully set, with the use of a vibrator, this knitting can be achieved provided the mix has water reducing/plastisizer admixtures in them. The vibrations will and agitation can reactivate the admixes allowing for the semi set concrete to become plastic again on the surface allowing for adhesion of the “new” concrete. There are other factors to take into account also, however in this case, I do see a “cold joint” but a clean and bonded one that will not have any issues.
Typically wall forms like this for residential buildings are poured at higher slumps (wetter) to allow for the concrete to fill in all of the mold without leaving a “popcorn” effect. The use of a vibrator for consolidation is also very common, which looking at the photo, both approaches were taken on this wall.

What I found to be interesting is the darker areas that start at the top, flow down the left side of the drain line then turn at the joint to the right.
Sloped Cold Joint Brick Pattern

It’s almost as if the contractor dumped a bucket of water down the forms prior to this top area being poured. I have seen contractors do this many times, with the mindset that it helps the two layers bond better. More often than not, the darker area is where the water and subsequent “cream” flowed. When concrete sets and cures under water, the end coloration will be darker than concrete left exposed to the air. If water is sprayed on the top of a slab for example and allowed to dry with the concrete, the color will be lighter. In well oiled wall forms, excess bleed water from the concrete cannot dry nor does it have anywhere to go, thus creating darker areas.

So to answer your question, the line you see would be considered a cold joint as others have stated, however in this case it’s a non issue…


The sloping line is just from the bottom portion being filled with concrete, then they just moved else where pouring, or ran a truck mt, come back to it later in the pouring of the foundation. We see it all the time around here,

As Marcel and others have indicated, it is a cold joint (to some extent, partially) resulting from one truck batch finishing and the next truck pouring from that point on. It’s perfectly normal and the larger the pour, the more of them you can expect to see. It is not an ideal scenario (in my opinion), but is almost unavoidable in most typical construction situations.

Observation: Suspect: Moisture capillary action stains.
Poor poured concrete barrier management.
Suspect: No adequate perimeter drainage.
Just my 2 cents.