Hello everyone. I recently purchased a 1928 home in seattle and since i moved in almost 2 years ago we have noticed the floors seeming to sag more and more.
Here pertinent house information: ~2 story house with a finished basement. (the top floor only has two small rooms slanted ceilings). The basement is carpeted cement floor, the exterior/walls of the house is brick. The basement floor is sloped to the center. The main floor also slopes to the center of the home. From what I can tell the joists are ~8-10" apart and appear to be 2x8's maybe larger. they run north/south in the house east/west runs a center main beam that is a 6x6. The east/west run is the longer run of the rectangular house.
at some point a staircase was installed to access the basement at the east end of the house and the main beam was chopped. Everything is dry walled so we can't tell exactly how well it was re-enforced but it looks like the main beam is well supported.
I've used a laser level at the worst part of the main floor and it registers a 1.6* slope. the areas of the floor around the walls seem level and firm, the closer you get to the center the more creaking and slopey it feels.
On the main floor in the center of the house near the staircase(to upstairs), the bathroom, and main bedroom- I notice that the floor has pulled away from the edges of the walls(like at the bottom of the entrance frame) rough estimate of this gap is about 1/4". We identified the center of the house and where we thought the main support posts would be in the basement. removed the dry wall and purchased a couple 20 ton jacks.
So far we have lifted this main beam in two different sessions and added metal shims to the top of the main support posts in the center of the basement. The two shims should now add up to a tad over 1/4".
However, it might be that day-to-day living in the house makes it so we don't notice any change but it seems that our efforts havent made much or any impact. I did not measure slope or anything prior to installing the shims. I did take a measurement from the center of the house to the ceiling, and a measurement from a spot close to the exterior walls and it seemed as though there was a 3/4" difference in my measurements.
Let me know if there is more information needed to aid in recommendations!