Chapter 27 Quiz: Foundation Waterproofing

Multiple Choice

1. You discover that your basement gets wet during July and August even during dry weather. The moisture is spread evenly across the walls and is worse when outside temperatures are high. The most likely cause is:

a) Subsurface groundwater with seasonal water table rise b) Surface water intrusion from poor grading c) Condensation of warm, humid exterior air on cool basement walls d) Crack infiltration from storm water

2. The plastic sheeting test (taping plastic against a damp wall for 48 hours) shows moisture forming on the side of the plastic facing the wall, between the plastic and the masonry. This indicates:

a) Condensation is the primary source of the moisture b) Water is coming through the wall from outside c) The wall has a coating that is trapping moisture d) The test is inconclusive

3. Which type of crack in a basement wall is the most serious structural concern and warrants calling a structural engineer before any waterproofing work?

a) Vertical hairline cracks in poured concrete b) Diagonal cracks at corners of window openings c) Horizontal cracks running along the length of a wall d) Shrinkage cracks in concrete block mortar joints

4. An interior drainage system (perimeter drain + sump pump) is best described as a system that:

a) Prevents water from entering the basement wall b) Stops hydrostatic pressure from building against the foundation c) Collects water after it enters and redirects it out of the basement d) Seals the wall surface to block water vapor

5. You receive two contractor proposals for a wet basement. Contractor A charges $9,500 for an interior drainage system and says the deal expires in 24 hours. Contractor B charges $11,000 for the same scope, spent 30 minutes asking about the history of the problem, walked the exterior, and recommended also extending a downspout before committing to the drainage system. Which contractor shows better professional behavior?

a) Contractor A, because a lower price indicates efficiency and confidence b) Contractor B, because thorough diagnosis before recommendation indicates professional process c) Neither, because the price difference is too large to justify the same scope d) Contractor A, because urgency often reflects honest cost pressures

6. Which of the following products is appropriate for reducing condensation-related dampness on basement walls but NOT rated for hydrostatic pressure?

a) Exterior liquid-applied membrane b) Polyurethane crack injection c) Hydraulic cement d) Masonry waterproofing paint (such as DRYLOK)

7. Polyurethane foam crack injection is preferred over epoxy injection for a crack with active water seeping through it because:

a) Polyurethane is stronger than epoxy b) Polyurethane works in wet conditions and remains flexible; epoxy requires a dry crack c) Epoxy is not rated for below-grade applications d) Polyurethane is significantly less expensive than epoxy in all cases

8. A proper sump pump installation includes which of the following components to protect against power failure during a storm?

a) A secondary pump wired to a dedicated circuit breaker b) A battery backup pump or water-powered backup pump c) A check valve on the discharge line d) A ground fault circuit interrupter (GFCI) outlet

9. Exterior waterproofing (excavation, membrane, drain board, footing drain) is MOST justified when:

a) You have condensation issues and want a permanent solution b) You are planning to finish the basement into living space and have confirmed hydrostatic pressure problems c) Your gutters are clogged and grading slopes toward the house d) You want to increase your home's resale value in any water-related situation

10. A window well's gravel drain layer at the bottom is silted over with fine debris. The likely consequence if left unaddressed is:

a) The window frame will expand and stick shut during wet seasons b) Water will accumulate in the well and eventually seep in through the window c) The window well wall will corrode from prolonged soil contact d) The basement dehumidifier will need to run more frequently

Short Answer

11. Explain in 3–4 sentences why fixing gutters and downspout discharge should always be the first step before investing in any basement waterproofing system, regardless of what a contractor recommends.

12. A homeowner is told by a waterproofing contractor that their basement needs a full-perimeter interior drainage system at a cost of $12,000. The contractor spent about 10 minutes inside, looked at the walls, and is presenting a proposal on a tablet. What are three specific questions the homeowner should ask before agreeing to anything?

13. What is hydrostatic pressure, and why does it cause water to enter a foundation even when the foundation has no visible cracks?

14. Describe the difference between a footing drain and an interior perimeter drain. Where is each located, and what problem does each address?

15. Your sump pump runs every 20 minutes even during a dry week with no rain. What are two possible explanations, and what would you check first?

Answer Key

Multiple Choice: 1-c, 2-b, 3-c, 4-c, 5-b, 6-d, 7-b, 8-b, 9-b, 10-b

Short Answer Guidance:

11. Surface water from roof runoff is the most common cause of basement moisture and is addressed with minimal cost ($20–$200) compared to drainage system installation ($5,000–$15,000). A contractor who doesn't ask about or check gutters and grading before proposing a major system may either be making a diagnostic error or choosing to sell what they install. The correct protocol is to address surface drainage first and reassess — many "basement water problems" disappear entirely with downspout management.

12. Acceptable questions include: (1) What specifically is causing the water intrusion in this basement — surface water, groundwater, or condensation? (2) Have you looked at the gutters and downspouts, and are there any surface drainage improvements that should be tried first? (3) Can you provide the specific pipe type, pump model, and membrane/liner materials that will be used? (4) What does the warranty cover, for how long, and does it transfer to a new buyer?

13. Hydrostatic pressure is the force exerted by a column of water against a submerged surface. When soil around a foundation becomes saturated, the water in the soil presses against the foundation wall and floor from all sides. Concrete and masonry are porous materials — they have tiny voids and micro-cracks throughout. Under sufficient hydrostatic pressure, water finds and exploits these pathways even in structurally intact walls. The pressure increases with the depth of water in the soil — the deeper the basement, the greater the potential hydrostatic force.

14. A footing drain (or French drain) is a perforated pipe placed at the base of the foundation footing, typically installed as part of original construction or exterior waterproofing. It intercepts groundwater before it can build up hydrostatic pressure against the wall and directs it away from the foundation. An interior perimeter drain is installed inside the basement along the perimeter, below the concrete floor slab. It does not prevent water from entering the wall but collects water after it enters and routes it to a sump pit. The footing drain addresses the problem at its source; the interior drain manages it after the fact.

15. Two possibilities: (1) The discharge pipe is recirculating — the water being pumped out is draining back toward the house and re-entering the sump pit. Check where the discharge terminates and whether a check valve is functioning properly. (2) The float switch is stuck in the "on" position, causing the pump to run continuously regardless of water level. Check whether the float moves freely and whether the pit actually has water in it when the pump is running.