You are specifying roofing materials for a home in Hilo with 120 inches of annual rainfall. Which underlayment system provides the best protection?
Correct Answer
C) Ice and water shield over entire roof deck
In extreme rainfall areas like Hilo, ice and water shield over the entire roof deck provides the most comprehensive water protection.
Why This Is the Correct Answer
Ice and water shield (self-adhering polymer-modified bitumen membrane) applied over the entire roof deck creates a fully bonded, watertight barrier. In extreme rainfall environments like Hilo — one of the wettest cities in the US — this full coverage eliminates any unsealed seams or penetration points that felt or synthetic underlayments leave exposed.
Why the Other Options Are Wrong
Option A: Double layer of 30-lb felt
Double-layer 30-lb felt provides more protection than single-layer felt but still relies on overlapping layers that can allow wind-driven rain infiltration, especially in high-wind/high-rain tropical conditions. It is not a self-adhering membrane and does not seal around fasteners.
Option B: Single layer of 15-lb felt
Single-layer 15-lb felt is the minimum code requirement in many standard climates but is wholly inadequate for 120 inches of annual rainfall. It is permeable, tears easily when wet, and provides no sealing at laps or fastener holes.
Option D: Synthetic underlayment with sealed seams
Synthetic underlayment with sealed seams is a significant improvement over felt and is suitable for many high-rainfall applications. However, even with sealed seams, synthetic underlayment does not bond to the deck surface, leaving it susceptible to wind uplift and moisture migration under extreme conditions. Ice and water shield provides superior protection for Hilo's extreme rainfall.
Memory Technique
Hilo = extreme conditions = extreme solution. Think of ice and water shield as 'shrink wrap for your roof deck' — it adheres directly and seals everything. When rainfall is off the charts, you need the one product that actually sticks to the deck rather than just sitting on top of it.
More Hawaii Questions
A concrete mix design for coastal construction specifies a water-cement ratio of 0.40. If 650 lbs of cement is used per cubic yard, how many gallons of water should be added?
A contractor is installing hurricane straps rated at 1,500 pounds each. If the calculated uplift force on a rafter is 3,200 pounds, how many straps are required with a 2.0 safety factor?
Hawaii Building Code requires special inspection for concrete placement in seismic design categories. What is the minimum frequency for concrete strength testing?
What is the maximum allowable deflection for roof rafters under design wind loads in Hawaii's hurricane zones?
Which roofing attachment method is specifically required in Hawaii's hurricane zones for asphalt shingles on residential construction?
A building in Maui requires hurricane straps rated for 175 mph winds. If each strap must resist 1,200 lbs of uplift force and you have 48 roof-to-wall connections, what is the total uplift resistance provided?
During construction of a beachfront property, you notice white crystalline deposits forming on the concrete surface. This indicates:
You discover expansive clay soil conditions during excavation for a residential foundation in Kona. The plasticity index is 28. What foundation system is most appropriate?
According to Hawaii building requirements, hurricane straps connecting roof trusses to wall plates must be rated for what minimum uplift force in high wind zones?
A concrete slab foundation in Hawaii requires a vapor barrier. Due to high humidity and frequent rainfall, what type of vapor barrier is most appropriate?
People Also Study
Business & Financial Management
120 questions · 70% to pass
Contract Administration
60 questions · 70% to pass
Project Management
60 questions · 70% to pass
Related Study Resources
Previous Question
Hawaii Building Code requires special inspection for concrete placement in seismic design categories. What is the minimum frequency for concrete strength testing?
Next Question
For a 2,400 square foot roof in a hurricane zone, if the code requires 45 psf uplift resistance and safety factor of 2.0, what total uplift force must the roof system resist?