One small addition to this house in Montclair, NJ cured all of its layout problems in one go. The addition was just big enough for a small mud room, laundry, and half bathroom. But it let us take the back door out of the sitting room. This made a huge difference in a small room made unfurnishable by five door openings. Suddenly, we had room for a sofa.
The old kitchen had been an awkward size: too narrow for an island but too wide for easy use. Now, not only is it considerably more spacious, but everything is within reach. We replaced its backsplash with a strip of windows to open up views to the backyard.