An applied force which tends to deform a body. May be tensile stress (pulling or stretching force), compressive stress (pushing or compacting force) or shear stress (opposite but offset parallel forces tending to produce a sliding motion).

SPFA believes that the path to a healthful, safe, high-quality and performing SPF installation travels through the hands of a knowledgeable, trained, experienced, and ideally PCP-certified professional contractor.