A spacer comprising: a) a wall insert weather sealing cup portion having a peripheral sidewall, and a bottom sidewall which seats on a structural frame of the building; and, b) a structurally reinforced bend prevention bolt spacing sleeve portion mated to fit within the cup portion, the sleeve portion having an central axial bolt opening therethrough. After an exterior side of the structural frame of the building is sheathed the sealing cup portion can be directly attached to the structural frame of the building through a hole drilled through a wall sheathing. When the sheathed wall is finished the cup portion can be sealed in the finish thereby preventing moisture from penetrating through the wall at the enlarged hole; and, when the addition is screwed to the existing building's frame, a substantial bending moment on the screws can be sustained by the structurally reinforced bend prevention bolt spacing sleeve portion.