The formulas to calculate the length of vertical bar needed are:

\[ Lb = 3.0 \cdot Aw \quad \text{(0.4 m spacing)} \]

\[ Lb = 2.1 \cdot Aw \quad \text{(0.6 m spacing)} \]

\[ Lb = 1.5 \cdot Aw \quad \text{(0.8 m spacing)} \]

Where:

• \(Lb\) is the length of vertical bar needed (m).
• \(Aw\) is the area of the wall (m²).