Decide on Single vs. Tiered Wall Design

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When building a retaining wall taller than 4 feet (the typical maximum for a gravity wall without permits), consider two main options: a single engineered wall or a tiered retaining wall. The presenter advises caution if a contractor only offers tiered options, as this might be a tactic to avoid the extra work and costs associated with engineered walls and permitting. A single engineered wall optimizes space both at the top and bottom but poses a trip hazard, requiring safety measures like fences or hedges. For tiered walls, a general rule of thumb is that the distance between a lower wall and the next higher wall should be at least twice the height of the lower wall. Failing to maintain this distance means the upper wall will exert surcharge pressure on the lower wall, requiring even more geogrid and fortification than a single wall would need, effectively increasing costs and potentially compromising stability. Tiered walls are appropriate when planting spaces are desired between courses, but these spaces must be wide enough for effective planting and maintenance (at least waist height, not too deep).