CSLB General Building (B)Site Work, Foundations and ConcreteEasy
A contractor constructs a concrete retaining wall to hold back soil on a sloped lot. During construction, small pipes are embedded through the wall near the base, sloping slightly downward to daylight on the exposed face. What is the primary purpose of these weep holes?
- ATo provide access for future wall inspections
- BTo allow rebar to be inserted after the pour
- CTo anchor the wall to the footing below
- DTo relieve hydrostatic pressure by draining water from behind the wall
Show answer & explanationAnswer & explanation
Correct answer: D. To relieve hydrostatic pressure by draining water from behind the wall
Weep holes allow water that accumulates behind a retaining wall to drain out through the wall face, relieving hydrostatic pressure that could otherwise crack or push over the wall. They are a critical drainage feature in retaining wall design.
Why the other options are wrong
- A. They are not intended as inspection access points.
- B. Weep holes are drainage features, not conduits for rebar placement.
- C. Anchoring is handled through footing design and dowels, not weep holes.
Weep Holes
Small drainage openings built into a retaining wall to relieve hydrostatic pressure by allowing trapped water behind the wall to drain out.
- Prevent hydrostatic pressure buildup behind wall
- Typically paired with gravel backfill and drainpipe
- Essential for retaining wall stability and longevity
Memory trick: Weep holes let the wall 'cry out' the trapped water before it pushes back.