Icedover Posted August 13, 2013 Report Share Posted August 13, 2013 I am building a new house and while at the site today I noticed what looked like a long large shift of the foundation. I have included some photos. If anyone could please look at them and tell me if this looks normal that would be great. If not, who could i get a second local opinion from? This is a post tension slab construction. If you need any more information I would me happy to try and find this out for you. Thank you in advance for your time. Click to Enlarge 47.87 KB Click to Enlarge 37.33 KB Click to Enlarge 42.55 KB Click to Enlarge 48.06 KB Click to Enlarge 43.86 KB Click to Enlarge 42.05 KB Click to Enlarge 34.45 KB Click to Enlarge 53.95 KB Click to Enlarge 48.53 KB Click to Enlarge 37.96 KB Quote Link to comment Share on other sites More sharing options...
Marc Posted August 13, 2013 Report Share Posted August 13, 2013 I've never seen that in post tensioning. Do you have a timeline for the pour and the tensioning event? How much time passed between them? Marc Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted August 13, 2013 Report Share Posted August 13, 2013 It looks like they placed stemwalls, then, later, placed the slab on top, so that it's overhanging the stemwalls by a fraction of an inch. If that's the case, then I don't see a problem. Have they tensioned the slab yet? Quote Link to comment Share on other sites More sharing options...
Icedover Posted August 13, 2013 Author Report Share Posted August 13, 2013 I've never seen that in post tensioning. Do you have a timeline for the pour and the tensioning event? How much time passed between them? Marc I don't have a presice time frame. I was out of town, but was told they were going to pour on Friday. The following Tuesday they had begun framing. Quote Link to comment Share on other sites More sharing options...
Icedover Posted August 13, 2013 Author Report Share Posted August 13, 2013 It looks like they placed stemwalls, then, later, placed the slab on top, so that it's overhanging the stemwalls by a fraction of an inch. If that's the case, then I don't see a problem. Have they tensioned the slab yet? Yes post tensioning has been done and the frame is in place. The thing that really concerned me was the thin layer of concrete underneath the devision line (only appearing in some of the photos) that makes me think the slab has sheared an inch or so. Quote Link to comment Share on other sites More sharing options...
Nolan Kienitz Posted August 13, 2013 Report Share Posted August 13, 2013 Tensioning of the cables happens at two intervals. Once within 7 days to put a slight tension in place and then at about 28 days they put the full tension on the cables ... once the concrete cures. That is when the PT cable ends are secured, cut and covered with a dollop of mortar. Often (far too often) framing starts with a day or two after the pour. Tensioning times are set out by the Post Tensioning Institute (PTI) and there should be documented reports of what was done when. Such documents are supposed to be signed off by people certified/trained by PTI. Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted August 13, 2013 Report Share Posted August 13, 2013 It looks like they placed stemwalls, then, later, placed the slab on top, so that it's overhanging the stemwalls by a fraction of an inch. If that's the case, then I don't see a problem. Have they tensioned the slab yet? Yes post tensioning has been done and the frame is in place. The thing that really concerned me was the thin layer of concrete underneath the devision line (only appearing in some of the photos) that makes me think the slab has sheared an inch or so. I'm not seeing anything like an inch of movement in any of those photos. Which one shows shearing of an inch? Quote Link to comment Share on other sites More sharing options...
David Meiland Posted August 13, 2013 Report Share Posted August 13, 2013 It looks like forms were placed against existing concrete, but not tightly enough, so that a bit of slurry went down into the gap and created a misalignment between the two concrete planes. They probably would have had to anchor the second form set to the first pour using blue screws or similar in order to avoid that. Instead, they tried to apply pressure with wood stakes or something else that doesn't quite work. Quote Link to comment Share on other sites More sharing options...
Icedover Posted August 14, 2013 Author Report Share Posted August 14, 2013 Tensioning of the cables happens at two intervals. Once within 7 days to put a slight tension in place and then at about 28 days they put the full tension on the cables ... once the concrete cures. That is when the PT cable ends are secured, cut and covered with a dollop of mortar. Often (far too often) framing starts with a day or two after the pour. Tensioning times are set out by the Post Tensioning Institute (PTI) and there should be documented reports of what was done when. Such documents are supposed to be signed off by people certified/trained by PTI. I guess they have not completed the final tensioning then. I assumed that they had to before the framing could begin. The pt cables are still exposed and stick out from the foundation about 2 feet. Should I be concerned that they began framing 4 days after pouring? Thank you for your response and insight. Quote Link to comment Share on other sites More sharing options...
Icedover Posted August 14, 2013 Author Report Share Posted August 14, 2013 It looks like forms were placed against existing concrete, but not tightly enough, so that a bit of slurry went down into the gap and created a misalignment between the two concrete planes. They probably would have had to anchor the second form set to the first pour using blue screws or similar in order to avoid that. Instead, they tried to apply pressure with wood stakes or something else that doesn't quite work. Hmmm as far as I am aware the forms were not removed. I don't see why they would have done so when pouring in the same spot back to back. That does make sense though. Quote Link to comment Share on other sites More sharing options...
Icedover Posted August 14, 2013 Author Report Share Posted August 14, 2013 It looks like they placed stemwalls, then, later, placed the slab on top, so that it's overhanging the stemwalls by a fraction of an inch. If that's the case, then I don't see a problem. Have they tensioned the slab yet? Yes post tensioning has been done and the frame is in place. The thing that really concerned me was the thin layer of concrete underneath the devision line (only appearing in some of the photos) that makes me think the slab has sheared an inch or so. I'm not seeing anything like an inch of movement in any of those photos. Which one shows shearing of an inch? I unfortunately have very little experience with foundations other than covering them with stone (did stone masonry for four years). The below picture was most worrying to me because of the thin outer layer that appears to be connected to both pour sites but angled and broken off. https://www.inspectorsjournal.com/forum ... hoto_2.jpg Thank you for your response. I apologize for my lack of experience and knowledge on this. Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted August 14, 2013 Report Share Posted August 14, 2013 It looks like forms were placed against existing concrete, but not tightly enough, so that a bit of slurry went down into the gap and created a misalignment between the two concrete planes. They probably would have had to anchor the second form set to the first pour using blue screws or similar in order to avoid that. Instead, they tried to apply pressure with wood stakes or something else that doesn't quite work. Hmmm as far as I am aware the forms were not removed. I don't see why they would have done so when pouring in the same spot back to back. That does make sense though. Typically, the stemwall forms are only as high as the top of the stemwalls. Later, new forms are placed to contain the edges of the slab. Quote Link to comment Share on other sites More sharing options...
Nolan Kienitz Posted August 14, 2013 Report Share Posted August 14, 2013 Tensioning of the cables happens at two intervals. Once within 7 days to put a slight tension in place and then at about 28 days they put the full tension on the cables ... once the concrete cures. That is when the PT cable ends are secured, cut and covered with a dollop of mortar. Often (far too often) framing starts with a day or two after the pour. Tensioning times are set out by the Post Tensioning Institute (PTI) and there should be documented reports of what was done when. Such documents are supposed to be signed off by people certified/trained by PTI. I guess they have not completed the final tensioning then. I assumed that they had to before the framing could begin. The pt cables are still exposed and stick out from the foundation about 2 feet. Should I be concerned that they began framing 4 days after pouring? Thank you for your response and insight. Typical and common when builders are in a hurry to get the structure built and closed and move the tax liability from their books to the buyer. In a perfect world it would be nice if things were done in a proper sequence of events and timing, but that is not the norm. I've seen framing starting as close as one to two days after the pour. Once the PT cables are fully tensioned they will be trimmed just under flush of the slab and covered over with a mortar mixture. Quote Link to comment Share on other sites More sharing options...
Marc Posted August 14, 2013 Report Share Posted August 14, 2013 There's nothing wrong with the framing beginning as soon as the concrete is hard enough to work on without damaging it. When I framed in Atlanta, we'd get out there as early as possible because a 16d ccs nail could still penetrate the concrete and anchor the wall. This was before anchor devices were required. Wait too long and you'll have to break out the cut nails. Marc Quote Link to comment Share on other sites More sharing options...
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