Stopped by a new development going up by my house today and saw a foundation that was poured last week. The foundation was all set up and yesterday there were 2×12’s all around the perimeter of the foundation which looked weird. Today I went back and realized they were actually forms to add an additional foot of concrete to the top of the foundation. It appears that it was poured too short and they added an extra foot.
My question is: is adding to the already set foundation walls recommended? I would think its not as structurally sound as a regular pour. Isn’t this asking for problems?? Here is a picture of what I’m describing. Is this normal???? You can see the color difference where the additional height was poured
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Replies
It's certainly not normal, but I doubt that it weakens it if the original foundation was designed and installed properly. Can't see what happened out in the middle. I doubt that a solid foot of concrete was poured over the total area. Probably has some sand fill out in the middle. How they extended the plumbing up through the added pour might be of concern. Connections under or in the concrete not good.
It's the foundation walls, not the floor. The perimeter walls were increased in height by a foot. That was what had me baffled.
Here is another view of the basement foundation walls
Note that foundations are often constructed from CMU, which is considerably weaker than poured concrete. And the portion of the foundation above grade is subjected to very little stress. Likely it was simpler to do it in two pours vs forming up the entire thing at once.
The only way this would be possibly acceptable is if vertical rebar was stubbed up from the bottom to the top or rebar dowel were epoxied into the bottom before the top was poured. If this were just an unreinforced cold joint it would be a problem.
It's called a "cold joint" concrete pour. It's not the first job it's been done on...and it won't be the last.
Who knows why they did it this way. It could have been for a number of good (and bad) reasons. For all anyone knows with the information you posted, the good reasons could have prompted design and approval of a structural engineer. In that case, it would hardly be "asking for problems" as you assume. Best not to assume.
My question is: Why do you care? Are you planning on buying the house?
If you do happen to really care, then why don't you stop in and ask the contractor who is building it. That would be the definitive way to satisfy your curiosity.