Final answer:
Built-up roofing may need flood coating in case of delamination, tar paper showing, or gravel embedded in tar.
Step-by-step explanation:
A built-up roofing may need flood coating under certain conditions. One reason is when delamination occurs. Delamination refers to the separation of layers within the roof, which can compromise its waterproofing capability. Flood coating helps seal the separated layers and restore the roof's integrity.
Another indication for flood coating is when the tar paper is showing. Tar paper is an essential component of built-up roofing systems, and if it becomes exposed, it can lead to water infiltration. Applying flood coating helps protect the tar paper and prevent leaks.
Flood coating may also be necessary if there is gravel embedded in the tar. Gravel is often used as a protective layer on built-up roofs, but if it starts to embed into the tar, it can create gaps and expose the underlying layers to water. Flood coating can help fill these gaps and prevent water damage.