Foundation, Anchorage, Bracing, and Stability
Stability is the theme that ties foundation, anchorage, and bracing together. The foundation must support the scaffold without settlement: firm, level ground; sills under base plates; base jacks for leveling; and attention to soft ground, slopes, and excavations. A trap is placing base plates directly on soft soil or on a slope without sills or jacks. Anchorage means ties to the structure at specified intervals; ties resist wind and overturning and must be installed as erection progresses. Never remove ties to make room for work without a qualified person's approval.
Bracing includes ledgers, diagonal braces, and plan braces that resist racking and lateral movement. Racking - the scaffold leaning or distorting - is prevented by adequate bracing. Overturning is resisted by ties, bracing, and proper loading. Traps include relying on guardrails for structural stability, omitting plan braces, and removing bracing temporarily without replacement.
Worked example / rule of thumb: Check the "three legs" of stability: (1) firm, level foundation with sills and jacks; (2) ties to the structure at the required spacing; (3) bracing in both directions. If any leg is missing, the scaffold is not stable. Also inspect for undermining by excavation or water before each shift.