Hardscape and Landscape Construction
The Hardscape and Landscape Construction domain tests whether you can build paving, walls, steps and edges that stay flat, plumb and drained through Canadian freeze-thaw cycles. Questions focus on base preparation, compaction, drainage, reinforcement, frost depth and the details that cause failures two or three winters later.
Base and paving
- Excavate to subgrade, place a separation geotextile, then install granular base compacted in lifts of roughly 100-150 mm. Thickness follows the intended load: pedestrian use needs less than a driveway carrying vehicles.
- Compact each lift before adding the next; one thick lift leaves loose material underneath that settles.
- Pave to about 1.5-2% slope away from buildings, install edge restraint on all open edges, and finish joints with polymeric sand worked in and activated per the manufacturer.
Retaining walls
- Bury the first course, batter the wall back slightly (commonly about 2.5 cm per 30 cm of height), and found the base below the regional frost depth, often around 1.2 m across much of Canada.
- Drainage behind the wall is mandatory: filter fabric against the soil, clear drainage aggregate, a perforated collector with outlets or weep holes, and compacted backfill in lifts.
- Install geogrid at the spacing the block manufacturer or engineer's table requires for that height and surcharge; cap the wall and respect maximum unreinforced heights.
Steps and concrete
- Keep risers and treads consistent, within code ranges (commonly 150-200 mm riser and 280-300 mm tread), and provide handrails where required.
- Specify air-entrained concrete for freeze-thaw exposure, with control joints and proper curing.
Worked example
A 1.2 m segmental block wall retains a planting bed. Correct build: excavate and compact subgrade, bury the first course fully, place filter fabric, add 300 mm of drainage aggregate with a perforated outlet at the low end, install geogrid per the manufacturer's table for 1.2 m, batter the wall, cap it, and compact backfill in thin lifts. Omitting the drainage is the most common cause of leaning and settlement.
Traps that cost marks
No wall drainage; compacting a single thick lift; shallowing the footing above frost depth; grading water toward the house.