Landscape Construction and Materials
Construction questions test material properties, assembly, and detailing. Know the major hardscape families: unit pavers (interlocking, clay brick, concrete), poured concrete, asphalt, natural stone (flagstone, bluestone, granite), and decomposed granite. Understand base course requirements: compacted aggregate base, bedding sand, edge restraint, and geotextile separation where needed. Traps include specifying pavers without edge restraint (they migrate), skipping compaction, or confusing flexible (paver) with rigid (concrete) pavement assemblies.
Know retaining wall types: gravity, cantilevered, segmental block, and timber, plus when each applies. Understand drainage behind walls (drain gravel, filter fabric, weep holes or drain pipe) and that walls over a certain height (commonly ~4 ft, varies by code) require engineering/permits. Recognize footing, frost depth, and expansion/control joint concepts. For wood, know decay resistance, connection hardware, and clearance from soil.
Materials traps: confusing nominal vs. actual lumber dimensions; assuming stone is uniform thickness; ignoring freeze-thaw durability; and forgetting that concrete needs control joints to manage cracking. Questions may ask which material is best for a given exposure (e.g., salt, freeze-thaw, heavy loads) - reason from durability and maintenance.
Worked rule of thumb: paver base typically 4 in compacted aggregate for pedestrian use and 6-8 in for vehicular; bedding sand about 1 in. Concrete slabs commonly use control joints at roughly 8-12 ft or in panels no more than about 1.5 times the slab thickness in feet squared. Always include edge restraint.
Review construction sequencing: excavation, base, utilities/sleeves, subgrade, finish, then planting. Questions often hide a sequencing error.