CSLB C-39 Roofing ContractorSafety and RepairHard
A roofing contractor is performing a tear-off and reroof on a commercial building. The existing roof is a gravel-surfaced built-up roof. During the tear-off, the crew discovers that the lightweight insulating concrete (LWIC) deck is saturated in several areas. What is the most critical immediate action the contractor must take regarding the saturated LWIC?
- ADrill weep holes through the LWIC to allow the trapped moisture to drain out.
- BRemove all saturated LWIC down to the structural deck and allow the deck to dry before installing new dry LWIC or rigid insulation.
- CApply a vapor barrier directly over the saturated LWIC and install new roofing.
- DInstall additional layers of rigid insulation over the saturated LWIC to encapsulate the moisture.
Show answer & explanationAnswer & explanation
Correct answer: B. Remove all saturated LWIC down to the structural deck and allow the deck to dry before installing new dry LWIC or rigid insulation.
Saturated lightweight insulating concrete must be completely removed. Installing new roofing over wet insulation will lead to premature failure due to trapped moisture, which will cause blistering, delamination, and degradation of the new roof system.
Why the other options are wrong
- A. Drilling weep holes might offer minimal, temporary relief but will not effectively dry out a substantially saturated LWIC deck and is not a recognized repair for this issue.
- C. Applying a vapor barrier over wet LWIC traps the moisture, leading to severe issues like blistering, delamination, and mold.
- D. Adding insulation over wet LWIC exacerbates the problem by encapsulating moisture, preventing drying, and leading to roof failure.
Saturated LWIC Management
Saturated lightweight insulating concrete (LWIC) must be completely removed and replaced to prevent premature failure of the new roof system.
- Trapped moisture causes roof degradation.
- LWIC loses insulating value when wet.
- Requires full removal and drying of substrate.
Memory trick: Wet insulation is a roof's worst foe, remove it all, let the deck dry slow.