Crack in floor and ceiling (with photos)

[Hamerhead6]

Information on my house. Built in 1973. Brick. 2,898 sq ft, single story ranch type. Below grade walls with four foot craw space and dirt. Sits on top of a hill overlooking a river where there are a lot of changes in humidity throughout the year. Also sits on an earthquake fault here in east Tennessee where there are many 1.0 to 2.0 earthquakes,barely or not even perceptible. But they still matter because the ground does move. This being a temperate climate, average daily humidity is 85 in the morning changing to 54 in the afternoon.

A few months ago a separation (Crack) began occurring in one of my hall ceilings next to our (unused) fireplace. Thought it may have been water but checked thoroughly upstairs and no water. Then the floor exactly over the ceiling crack began separating. Here are some photo's then questions at the bottom.

Crack in floor. The floor is a walkway between the Den and the LR and rest of the house. The crack is the entire distance between one wall and the fireplace. 4'9".



This was flat, the side of the floor up against the fireplace.



The ceiling directly above the floor crack.





Craw Space photos



Couple of notes then my questions.

In the winter nothing moves. In the spring (temps from 60-80) and summer (upwards of 100 degrees), you can walk through the house normally and everything glass shakes.

The separation in the floor and ceiling is new, in the last two years there has been some minor separation but this particular separation has happened very recently.

Questions.

What could be the causes of this separation/crack?

Should I add leveling jacks?

What else or what should I be looking for or considering?

Thanks

 

[oldognewtrick]

The picture of the block pier, it looks like there's a space between the block and the beam.

 

[ChrisAtTech]

Are the cracks perpendicular or parallel to the floor joists in the crawlspace? If it were my place, I wouldn't be too concerned with the current size of the crack as your description of the house location (on a hill, next to a river, with slight earthquakes) means some extra settling and changes can be expected. I'd monitor the crack in different places including measurements of how wide it is at specific points and measure the width on a monthly or quarterly interval to determine the rate of change. Also, mark the endpoints of the crack and monitor if that expands. If the crack continues to expand then I'd get a structural engineer out to take a look. The other thing I'd do is a thorough examination of the foundation, exterior, crawlspace, and interior to look for any other cracks or signs of movement. Then, monitor the size of any other spots found.