Thread: Cold joint?

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I can't make out too much from pics 2 & 3.... at first pic 1 seemed pretty severe but then I realized how close up it was. Still, that looks like more than just a cold joint.... but again, I can't tell too much from the pic. I'd need some more info to know for sure.

Any signs from inside?

Is it a basement or a crawl?

How old is the house?

Sloped floors, walls or anything of note in this area of the house?

I'd try to get to the sill plate and foundation inside this area and see what was going on. If all is well in all of these areas and none of the questions above raise more questions I'd lean towards thinking it was a bad pour or cold joint and was okay.... but, again, it's tough to say from those pics.

What is commonly called a cold joint is when fresh concrete is poured on top of (or adjacent to) concrete that has already begun to set up. This often happens in a large pour (e.g., a foundation wall or a large slab) where it takes a good deal of time for the pour to make the circuit back to the starting point. A cold joint can also occur when a delay occurs during the pour (e.g., a concrete truck is delayed or a blowout occurs in the formwork).

The interface between the two pours is the cold joint. The cold joint is noticeable by the difference in color of the concrete on either side of it. Cold joints are not normally a structural concern. (After my episode with a leaking honeycomb the other day I would not rule out the possibility of a cold joint leaking.) Good practice is to vibrate the concrete to blend the new and old concrete if possible to avoid a cold joint or to insert rebar into the old concrete to create a structural bridge between the two pours. If it is anticipated that the first-poured concrete will be set up beyond the point of the new concrete adhering to it a keyway can be formed into the first pour (possibly along with rebar dowels) to make a good structural connection between the two pours.

In Pic 1 it is hard to tell if that is a cold joint, a new foundation poured on top of an old foundation or parging on the upper part of the foundation.

I can't make out much from Pic 2. It looks like the bottom of the foundation flares out or is leaning quite a bit. Is it possible that the original foundation was stone and a concrete foundation was poured on top of (and perhaps inside of) it? When was the house built? (Stone foundations are not common after 1930 or so.)

In Pic 3 what you are looking at may be either a buttress or a mistake. It could also be the remnants of the foundation of a room that has long since been removed.

Hope that helps. It is hard to tell much from your pics.