My wife and I own an italianate farmhouse in New York State. Originally built circa 1850, it burned down around 1880 and was rebuilt a few years later. The foundation is fieldstone, the main structural elements (mud sill, support beams) are timbers, but the rest of the house is balloon framed with true 2x4s on the wall and 2x10s for the floor. It’s 2 stories with an attic and about 3300 square feet. I’ve been room by room renovating the house and have recently started work on the back half of the second floor. The house has a ~8′ deep basement under the majority of the home, but the rearmost 11′ of the house sits above a crawl space with a fieldstone foundation.
During the demo work I discovered that the rearmost 11′ of the house slopes down toward the rear of the house with a 3″ fall over the course of that 11′. This 3″ fall is similar on the first and second floors of this section of the home. I’ve checked the structural elements of this section and there doesn’t seem to be any significant rot or damage to the timbers and the crawl space foundation walls look intact and sound. Given that it appears to affect the entire section and there isn’t any obvious structural issue, my suspicion is that the foundation wall under the rearmost wall of the home was probably not built as deep as the full basement (given that it’s a crawlspace) and with the local freeze/thaw cycles probably just sank into the ground that 3″.My plan for that rearmost 11′ section of the home is to have a master bath and a large closet on the second floor and a kitchen on the first floor. So there will be a lot of weight and nice finishes in this section of the home. So before I start to put all this nice heavy stuff in I want to make sure that the subsidence problem is addressed.
To that end I see two possible paths:
1. I count on any subsidence being complete and done, the house dropped what it’s going to drop and it’s not going anywhere. It’s been sitting here successfully for 140 years and it’s going to be fine. I modify the floor joists as needed to level out the floors and start adding the rooms and finishes.
2. I count on the subsidence continuing and therefore I need to reinforce the foundation. I know there’s several correct ways to go about this (jack up the house, new foundation wall, put in piers, etc) I pick one and move forward.
What path would you pick? What have you seen with similar age houses in terms of foundation movement/sinking? Is subsidence typically an ongoing process or does it usually occur over the first few years/decades and then stabilize (barring siting the home on top of a giant cave or sinkhole)? Would there be a way to evaluate if the subsidence is an ongoing problem or one that’s resolved? Is there a third path where I add some bracing or a beam that would prevent the house from dropping further without redoing a large section of the foundation? Thanks for the help.
