Underpinning
Underpinning , noun
1.
The act of one who underpins; the act of supporting by stones, masonry, or the like.
2.
(a) (Architecture) That by which a building is underpinned; the material and construction used for support, introduced beneath a wall already constructed.
(b)
(Architecture) The foundation, esp. of a frame house. [Local, United States]