I run into this every now and then and I wanted to see how you guys report this.
This is a poured foundation on a ranch home built around 1960. From the exterior the foundation wall appears to curve or bow inwards near the middle of the home at the front wall. There is about a 1 1/2" gap between the wall sheathing and the foundation near the middle of the home, however that gap reduces in size as it approaches the corners of the home where the wall sheathing is tight up against the foundation. At first glance it could appear that the foundation has been pushed inwards an inch and a half, however it could have also been built this way. No notable cracks were found, at least where it was visible, and of course the basement is completely finished so nothing was visible inside. Its a foreclosure so no past history is available.
Any advice on determining if it was built with a curve or if it has moved? I know on newer homes the floor structure is usually tied to the foundation, but on homes in this age range around here that isn’t always the case.
It sounds like soil pressure where the wall is weak to horizontal stress in the middle of the run. The corners are reinforced by the perpendicular walls that help hold them back.
If the floor system was adequately secured to the foundation you would probably see an outward bow on the wall opposite. Did you see anything on the other side of the house?
Was there a drive along that front side of the house?
That much of a bow inward is substantial and needs to be reported and repaired to maintain structural integrity of the foundation wall by a qualified foundation contractor who uses the services of a structural engineer.
No driveway, no sidewalk, and properly graded soil at the front of the home. There was a similar gap at the rear wall of about 3/4" of an inch. The rear wall was visible inside the basement and there was no substantial cracks other than a hairline vertical crack with no displacement. My gut feeling is that it was built this way but I have no way of knowing. Either way it was written up as a further evaluation needed.
Bad formwork, very common. Less common is premature back-filling which would crack concrete green enough to move that much. The only way to know for sure is to tear out some drywall and look for cracking on the inside of that wall. Since there’s another wall with a similar problem and no crack, my bet would be on bad formwork.
If it’s been like that since 1960 it probably isn’t going to fail or change any time soon. That kind of condition would very seldom develop after 40 or 50 years.
As Larry and others have stated - premature backfilling of the foundation wall is often the cause. The foundation walls must be laterally reinforced either by the floor framing system or by an internal side temporary brace system.