Foundation (engineering)
Foundations are designed to have an adequate load capacity depending on the type of subsoil/rock supporting the foundation by a geotechnical engineer, and the footing itself may be designed structurally by a structural engineer. The primary design concerns are settlement and bearing capacity. When considering settlement, total settlement and differential settlement is normally considered. Differential settlement is when one part of a foundation settles more than another part. This can cause problems to the structure which the foundation is supporting. Expansive clay soils can also cause problems.
Roaring Spring, Pennsylvania
Sixty-Nine (69) Percent of the foundations are stone, which supports almost all buildings erected before ca. 1920. While stone as a foundation material is common in pre-1920s buildings, its use as a structural material is very rare due in large measure to the common availability and economy of sawn lumber, and the age of the community which postdated the vernacular use of stone as a regional building material. As a foundation material, stone was generally replaced in the 1920s by cast concrete block (generally molded as a rock-face ashlar), which in turn was succeeded by cinderblock and poured concrete after the 1940s. After concrete and cinderblock, concrete block is the third most common foundation material (almost 3 percent); it was also employed for garages, outbuildings and additions in the 1920s and 1930s. Most contributing houses bear full front porches, the vast majority of which are intact. Original roof materials were generally slate or tin (raised seam, corrugated, or pressed pattern). While a fair number survive, many others have been replaced for economy with modern asphalt shingle. Even where original slate roofs have been replaced, many decorative slate shingles covering the fascia boards of large window gables survive, especially on turn-of-the-century Gothic Revival types. This decorative practice, fairly common on houses built from 1900 to 1920 by the Roaring Spring Planing Mill Co., can be seen in other period buildings around the Morrisons Cove area where the Planing Mill's contractors are known to have worked.