in removing our panelling, we noticed about 1/3 of the vertical studs in the freestanding walls were -- at some point in the top/bottom run -- sliced nearly 1/2 to 3/4 of the way through with plywood plating added over the sides to strengthen the now weakened stud (like a jack-stud).
if this were on one stud, i'd chalk it up to careless measurements meets thrifty framer and the desire to be resourceful with wood. however, it's so prevalent, it seems almost purposeful.
any ideas on why?
I am not sure "why." But my question is "what are you going to do about it now?"
My advice is to put some metal shim because I would hate for the support studs to break at those cuts.
Looking at your home, I can tell it's going to be beautiful! Thankfully the paneling was not painted over.
just got a tip from my father-in-law: "...'slashed' 2x4s is an old carpenters trick to straighten warped timber prior to putting on drywall or plaster. It normally is an indication of quality construction because most framing timber will bend depending on moisture content, moisture loss rate, and loading. Most houses where this is practiced were framed, encased, and roofed...and then allowed to 'season' before interior wall treatments were applied. The carpenters would then run a straight edge along the wall and correct any studs using this technique. The 'quality construction' dimension of this is that the overall construction timeframe was lengthened to make sure that the framing was allowed to adjust, and then corrected...made the wall finish more planar and square."
as to what i'm doing about it now: i'm finding the questionable studs and reinforcing them with 1/2in ply plating on the sides and/or simply replacing the stud or running a new one adjacent to the old... to be honest, the 1/2in ply plate with some screws (rather than nails) and some construction adhesive has strengthened them quite a bit... probably equal to their original strength.
hopefully this will only be on the paneled walls (which in my design are few... and unfortunately, although not painted, the original panels were in such a condition that all will need to be replaced....)