A Basement Mystery

I've taken a few days away from the basement demo because 1, I recently had to engage in a tree-trimming extravaganza, prompted by a sizable tree limb snapping off and getting hung up - directly over the garage - in one of the back yard oaks, 2, I wanted to button up a few spots on the roof that needed patching, and 3, I've still got some undetermined MCL issue; after hauling a legit 5+ tons of crap out of the yard and basement, the left knee isn't currently on friendly terms with the rest of my body.

The break in the action has given me a chance to inspect and think through what I've uncovered. So far, the basement demo has yielded quite a few interesting finds, albeit head-scratchers. For example, there's a spot by the rear wall, below what are now kitchen cabinets, where the framing indicates something heavy was going on above it; the mortise and tenon joints used to join the joists together are pretty rad, but what was the reason for beefing up or boxing around the framing in that area?! 1st floor radiator? Stove? Fireplace? 

The biggest basement mystery, by far, and one that impacts my future plans for this house the most, is a wall. Why is it a mystery? Because it's a full-blown stone wall, with a brick wall above it on the first floor - the same as all the EXTERIOR walls - in the INTERIOR of the basement/house. 

The wall cuts right across the middle of the basement - shown by the yellow line -  separating the space into a northern half and a southern half. It's got a doorway through it with what has to be about a 16" deep jamb, and it runs from the west foundation wall to the east foundation wall, floor to ceiling.

I've seen interior stone foundation walls in much larger, older homes than this, stuff that's 2 or 3 stories and thousands upon thousands of square feet. But in a house this size and shape, single story...never seen it before. 

There are only a few quasi-reasonable explanations:

1. This was originally the rear of the house, or 
2. This wall was constructed for lateral stability, or
   
3. The builder hated his crew and made them build a stone wall when it wasn't necessary.

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Let's tackle possibility #1.

​The water service to the house enters through the basement floor on the south side of this wall, a few feet to the left of the doorway, and the service appears to be original - it's a lead pipe - to whenever plumbing was introduced to the house. 

Similarly, the basement stairs - which are original - are entirely on the south side of the wall, also supporting the idea that the stone wall could have been the original back wall of the house. 

​If the stairs, water service, or anything like that fell on the north side of the wall, then it obviously wouldn't have been the back end of the house.

Looking at old maps, which almost always accurately portray the general building footprints, the 1883 map shows the house as being a different shape than the 1903 map. Is it possible that the interior stone foundation wall was originally, at least in part, the back side of the house and the angled, bumped-out section of the house was added at a later date? 

1883 city atlas

1903 fire insurance map

Conversely, the door jamb and (removed) door in the stone wall do not appear to be of the exterior variety, nor was there any presence of wear and tear typical of exterior basement-level doors, which supports the idea that this was not originally the back end of the house. And the jamb wasn't added after the fact, the plaster and stone are too tight to it; the evidence of square cut nails tells me she's been there as long as that wall.

Is it possible that the basement was originally separated by the stone wall for a utilitarian purpose? The south section could have been accessed by the interior stairs, and the north section could have been accessed by the exterior/walkout stairs. The basement was originally given a plaster finish, and although the house was billed as a single-family, is it possible that the basement was always the shape shown in the 1903 map and the stone wall and doorway served to separate living quarters, or separate basement space from some type of root cellar?  

Tough to say at this point. Maybe further demo and investigation will give me more clues to work with. Maybe the brick wall on the first floor, directly above the stone wall, will give me some information when I tear into it. ​

Then there's point #2, lateral stability. The house does make use of a few steel rods running across the building above the ceiling, which is common for this era of construction; if you ever see metal stars on the sides of old buildings, those are actually big, fancy washers on either end of the steel rods. My house has 3 rods, if I remember correctly, which provide lateral bracing at the points of the wall farthest from the foundation, where brick walls tend to get a little loosey-goosey if not supported laterally.

But to brace things laterally like that in the basement, and first floor of the house via masonry? Never seen it, not for that purpose anyhow. Walls get braced at points furthest from where they're most stable, not at the foundation level. I don't think the mystery wall's existence has anything to do with stability.

As for point #3, having moved several big foundation stones from random spots in the back yard (why they're there, I have no idea), I can tell you that those suckers are heavy. Stupid heavy. There is zero reason to use them for anything unless it's absolutely necessary, and if the mystery wall really didn't serve any purpose, then whoever called the construction shots wanted to make his people really, really earn their income. I can't imagine this was the case either.

So...no conclusive proof of point #1, no real likelihood that point #2 was the case, and no way point #3 is in play. 

​What am I missing? What options have I not thought through? 

The truth is, the mysterious stone wall in the basement is sort of inconsequential...but the brick wall above it, cutting the house in half and also a total mystery...she presents a little bit of a design challenge.

If I can figure out why the stone wall exists, or existed, that may help me figure out what I can and can't do with the brick wall above it.