If you have access beneath the room you can jack up the portion of the floor that is descending. You should probably investigate why this is occurring anyway.

You cannot caulk 1" of space.

Maybe not the best option but consider adding a 3/4" round moulding trim (or larger) at the floor base to disguise the baseboard height difference.

You get a plain trim piece the same thickness as your baseboard. You scribe it to the floor and install it on the wall. It will cover the triangle of wall from the lowest point in the floor up to the highest point in the floor. It will be level on top. Install your normal baseboard above that.

Flextrim.

If you’re not going to fix the cause, then scribe the moulding to the floor and paint it the same color as the wall. There is a hump in it, though; look at the gap in the left corner…and the windows. Btw, you should be using a longer level (or a laser level).

The house is 130 years old. The floor is not sagging or sinking in that corner. There is a stone wall under that part of the floor where the gap starts and goes under the whole house. Floor joists end on that stone wall and start again and continue to the outside foundation wall that is not the same height as the stone wall in the middle (off center) of the floor. Fixing this is possible, for a hefty price. we were told by a foundation expert who is very reputable in northwest ohio and southern Michigan, if we’re going to start fixing parts of the foundation, it will cause issues on the other side of the house and it woild be best to leave it alone because its not a foundation issue.

Thank you all for the suggestions!

With a very old house, I think Jennifer’s idea is the best. And it looks like the perfect spot for a sofa!

Just scribe the molding to the floor and paint it the color of the wall. Having it white is not what you should do in this instance.

You just add a little shoe molding to fill the gap..paint it white.

Yes, this is what shoe moulding was invented for.

Looks like shoe won’t cover all of it. Had this problem at my office- a 1902 addition over an 1850 grocery store. Some baseboards got wood added to hide a low spot, some got wood removed to hide a hump. Once furniture is in no one is the wiser.

Shoe mould can be fabricated for the particular application. Need not be stock dimensions. In our former office which had a lot of variation in the slab, we used colonial stop moulding as shoe moulding.

IMO Jennifer has the right answer and I agree no white just the same as the wall color and you can do that on one wall and then add your furniture no one will ever know .

Scribe means you make a pattern and cut the molding to fit.