During the life of a structure, it tends to settle into the ground and soil below it as erosion occurs and time passes. When there are two structures adjacent to each other, the neighboring adjacent structures tend to lean on each other as they settle.
The two structures essentially become each other’s supporting wall. Thus, when one of the adjacent structures is removed, it leaves the remaining structure vulnerable to structural failure since the weight of the remaining structure no longer has the support in which it previously leaned a portion of its weight on.
To address this during new construction, temporary steel beams are placed and anchored to remaining structure to maintain the support that has now been removed.