I inspected a house recently with some significant drywall cracking. House is about 40 years old. The cracks are indicative of differential settlement, and I confirmed by analyzing the existing framing. The deformed shape of the house doesn't make sense with my analysis unless I assume a displacement in my support. So I'm confident that the issue is in the foundation, but I'm trying to make sense of the timing.
As I said, the house is about 40 years old, built in 1979. The current residents are the original owners who commissioned the house to be built. They said that they have had no cracking of any kind until about 2014. That's when these cracks appeared, and have grown progressively worse. In the last 2 years one of the doors from which the cracks emanate has jammed and is completely inoperable. I've seen a lot of settlement issues, but for a house to have no noticeable movement for 35 years and then suddenly start settling seems a bit odd.
There have been some changes over time, most relevant was the addition of a porch roof and elevated patio, but that was done in the late 90s. In 2011, we experienced a once-in-a-generation seismic event. This is eastern Virginia, so that just means we felt it. The sort of thing that the average Californian wouldn't notice, and more than a few people just thought they were having a case of vertigo. We're about 140 miles away from the epicenter.
We have clayey soils - that and muck. Typical depths to marine sediments that a pile can bear in are around 30 to 40 feet. Given the proximity of this house to a river, it's probably closer to 60ft. What is the likelihood that a minor seismic event like this could trigger additional consolidation in clay soils? Given the the fact that these events are so rare, I haven't taken much time to study the goetechnical ramifications, so I appreciate any help you guys can give.
As I said, the house is about 40 years old, built in 1979. The current residents are the original owners who commissioned the house to be built. They said that they have had no cracking of any kind until about 2014. That's when these cracks appeared, and have grown progressively worse. In the last 2 years one of the doors from which the cracks emanate has jammed and is completely inoperable. I've seen a lot of settlement issues, but for a house to have no noticeable movement for 35 years and then suddenly start settling seems a bit odd.
There have been some changes over time, most relevant was the addition of a porch roof and elevated patio, but that was done in the late 90s. In 2011, we experienced a once-in-a-generation seismic event. This is eastern Virginia, so that just means we felt it. The sort of thing that the average Californian wouldn't notice, and more than a few people just thought they were having a case of vertigo. We're about 140 miles away from the epicenter.
We have clayey soils - that and muck. Typical depths to marine sediments that a pile can bear in are around 30 to 40 feet. Given the proximity of this house to a river, it's probably closer to 60ft. What is the likelihood that a minor seismic event like this could trigger additional consolidation in clay soils? Given the the fact that these events are so rare, I haven't taken much time to study the goetechnical ramifications, so I appreciate any help you guys can give.
