As more homeowners stay put longer, many are hitting a wall—literally. One in 4 say they need more space, according to one survey, with another quarter reporting they outgrew their home just two years ...

The Merzes, both architects, moved into 48 Willow Place after its completion, and designed separate, architecturally comparable homes on two other nearby parcels. Now, a rooftop addition to 48 Willow ...