Chapter 2 Quiz
Multiple Choice
1. Why must foundation footings be placed below the frost depth?
a) Concrete cures better in unfrozen soil b) Building codes require a specific number of feet between footings and the water table c) When soil water freezes it expands, and the expansion can lift a foundation — a phenomenon called frost heave d) Frost makes soil harder and therefore a better bearing surface for footings
Correct answer: c
2. A post-tensioned slab differs from a conventionally reinforced slab in that it:
a) Uses wooden beams instead of steel rebar b) Contains high-strength steel cables that are tensioned after the concrete cures, putting the slab in compression c) Is poured in sections with control joints between them d) Uses a thicker layer of gravel base and no vapor barrier
Correct answer: b
3. Hydrostatic pressure on a basement wall is best described as:
a) The downward weight of the building transmitted through the foundation wall b) Pressure from the weight of frost in the soil during winter months c) The horizontal pressure exerted by water or water-saturated soil against the wall d) The suction force created when interior basement humidity is lower than exterior humidity
Correct answer: c
4. Which type of foundation crack is MOST concerning and requires structural engineering evaluation?
a) Hairline vertical cracks in poured concrete walls with no displacement b) Shrinkage cracks radiating from re-entrant corners in a concrete slab c) Horizontal cracks in concrete block basement walls d) Stair-step cracks in a concrete block chimney at the mortar joints
Correct answer: c
5. An "encapsulated crawlspace" is one that:
a) Has been fully excavated and converted to a basement b) Has a heavy vapor barrier covering the soil floor and walls, with foundation vents sealed and humidity controlled c) Has had all organic material removed and the floor lined with concrete d) Has been treated with pesticides to prevent termite infiltration
Correct answer: b
6. Differential settlement is more problematic than uniform settlement because:
a) Differential settlement causes the building to sink faster overall b) It puts racking forces on the structure, causing visible damage to walls, doors, windows, and framing c) Building codes allow uniform settlement but prohibit differential settlement d) Differential settlement always indicates expansive soil, which cannot be remediated
Correct answer: b
7. Which of the following drainage practices most directly prevents water from saturating foundation soil?
a) Applying waterproof paint to the interior of basement walls b) Installing an interior drain channel and sump pump c) Maintaining gutters and extending downspouts at least 6 feet from the foundation, and ensuring grade slopes away from the building d) Sealing foundation cracks with hydraulic cement from the interior
Correct answer: c
8. Why is a waterproofing contractor a potentially unreliable sole source of advice on a horizontal foundation crack?
a) Waterproofing contractors are not licensed to work on foundations b) They can only install interior drainage systems, not exterior waterproofing c) They are in the business of selling drainage systems and are not qualified to determine whether a crack indicates structural failure requiring a different type of repair d) Horizontal cracks never have a waterproofing solution, so they have no applicable product
Correct answer: c
9. Expansive clay soils are a concern for foundations because:
a) They drain too rapidly, removing moisture support from under foundations b) They cannot support the weight of residential buildings c) They swell when wet and shrink when dry, exerting variable pressure on foundation elements and creating voids beneath slabs d) They freeze at higher temperatures than other soil types, increasing frost depth requirements
Correct answer: c
10. A basement bedroom without a code-compliant egress window is problematic because:
a) Building codes require all bedrooms to have at least two windows for ventilation b) It creates a fire-trap situation where occupants cannot escape if the single exit is blocked, and represents a code violation c) Basement bedrooms are never legally permitted under any building code d) Insurance companies refuse to cover any bedroom below grade
Correct answer: b
Short Answer
11. Describe the difference between interior waterproofing and exterior waterproofing for a basement, and explain when each is appropriate.
Model answer: Exterior waterproofing applies a membrane or coating to the outside of the foundation wall, preventing water from ever reaching the wall. It typically includes drainage board and perimeter drain tiles at the footing. It requires excavating around the foundation, making it expensive ($20,000–$50,000+), but it's the most thorough solution for serious active water problems. Interior waterproofing installs drain channels inside the basement perimeter that collect water that has already crossed the wall, routing it to a sump pit where a pump ejects it. It doesn't stop water at the wall — it manages water that has entered. Interior systems cost $8,000–$20,000 and are appropriate for many common basement moisture situations where water infiltration is manageable. The choice depends on severity, budget, and accessibility of the exterior.
12. List three interior symptoms of a home that may indicate differential settlement, and explain how to distinguish these symptoms from normal seasonal wood movement.
Model answer: Three symptoms: (1) Doors that stick or fail to latch properly, particularly at the top or bottom corners; (2) Diagonal drywall cracks running from the corners of window and door openings; (3) Visible floor slope detectable with a level or by rolling a ball. Normal seasonal movement is caused by wood swelling and contracting with humidity changes — a door that sticks in humid summer months but operates fine in dry winter months is typically not a foundation concern. The warning signs of foundation movement are: symptoms that are progressive (getting worse over time, not fluctuating seasonally), multiple symptoms occurring together (several sticky doors plus drywall cracks plus sloped floors), and displacement in cracks or structural elements that doesn't resolve seasonally.
13. Explain the moisture problem endemic to crawlspace foundations and describe the modern solution.
Model answer: Crawlspace foundations have a persistent moisture problem because the soil floor continuously releases water vapor upward. The traditional solution — foundation vents in the stem walls — was intended to allow humid air to escape, but in warm humid climates the incoming air is often more humid than the crawlspace air, making venting a net moisture contributor. The result is chronically high humidity that leads to wood rot, mold, and pest activity. The modern solution is crawlspace encapsulation: a heavy-duty polyethylene vapor barrier (typically 20-mil) covers the entire soil floor and is sealed up the stem walls, all foundation vents are sealed closed, and humidity is controlled either by conditioning the space with a small supply of air from the HVAC system or with a dedicated dehumidifier. An encapsulated crawlspace eliminates ground moisture as a humidity source, protects structural wood from rot, improves floor warmth above, and creates a clean, accessible maintenance space.
14. A homeowner discovers a horizontal crack in their concrete block basement wall. The crack is about 6 feet long and roughly 1/8 inch wide. One side of the crack appears to be pushed very slightly inward — perhaps 1/16 of an inch. Who should they call first, and why?
Model answer: They should call a structural engineer — not a general contractor, not a waterproofing company, and not an internet forum. A horizontal crack in a concrete block wall indicates lateral earth pressure (hydrostatic pressure, expansive soil, or frost) pushing the wall inward. This is a structural failure mechanism, not a moisture problem. Even with minimal initial displacement, horizontal cracks are progressive — the same force that caused the crack continues to act on the wall. A structural engineer will: assess the underlying cause, measure displacement accurately, determine whether the condition is stable or progressive, and recommend the appropriate repair (which may range from drainage improvement to carbon fiber straps to excavation and wall repair). A waterproofing company may recommend a drainage channel, which does not address lateral pressure. A GC may patch the crack, which does not address the cause. The structural engineer's report costs $350–$800 and ensures that any subsequent repair actually addresses the real problem.