Foundation, Ground Conditions, and Stability
Ground and base
A scaffold must bear on firm, level, drained ground. Use sole boards/sills to spread load, base plates on standards, and adjustable base jacks to level. Avoid soft ground, backfilled trenches, drains, and slopes unless properly bridged or designed. Foundation failure causes differential settlement, leaning, and collapse.
Stability
Ties anchor the scaffold to the structure and resist wind and overturning. Braces (facade, end, plan) stiffen the frame. Guy wires may stabilize free-standing scaffolds. Mobile towers need outriggers/stabilizers and must not be moved with people or materials on them. Cantilever scaffolds rely on counterweights or structural anchors.
Traps
- Assuming ties are optional; they are structural, not just restraints.
- Using a single small sole board under a heavily loaded standard.
- Ignoring drain covers or manhole locations under standards.
- Believing a mobile tower is stable without outriggers.
- Forgetting that wind acts on sheeted or netted scaffolds, increasing tie loads.
Rule of thumb
Every standard needs a base plate on a sole board sized to the ground bearing capacity; every scaffold needs a tie and bracing plan. If the ground is doubtful, stop and get it assessed.
Worked example
A standard carries a design load of 6 kN on soft clay with a bearing capacity of 50 kN/m². Required sole area = 6/50 = 0.12 m², so a sole board of at least 0.4 m × 0.3 m is needed; a 150 mm base plate alone would overstress the ground.