Here is a starter checklist for anyone inspecting a roof for possible issues:

Coating deterioration—If a roof component looks like it has been peeled or chipped, that might indicate previous ponding water (post-rain water on the roof for more than 48 hours).

Supports—Check for significant levels of debris and dirt on the roof, especially where it connects and relates to the stone ballast (support).

Check membrane conditions—The membrane is the felt weatherproofing layer of the roof. It can become corrupt or can erode due to debris and dirt build-up, entrapped moisture, and other conditions. It can also become loose and unsealed.

Perimeter edges, copings, base flashings, counterflashings and area dividers–These roof components require great attention to detail during construction and, as a result, tend to become more problematic than other areas of the roof as time passes.

Flashings—Make sure they are sealed and free of holes and other problems.

Sealants—Check sealed areas for voids and deterioration at every joint and end.

Flashing and sealant conditions should also be checked around any roof element that sticks or juts out from the roof (i.e. gables, sunroofs, gutters, etc)

Drains, scuppers and gutters—These need to be checked more regularly to make sure precipitation, dirt and debris are exiting the roof properly.

Staining—Staining on any component of the roof might indicate previous water ponding and should be inspected carefully.

Any signs of failure or problems in a house should be dealt with immediately. Sometimes what looks like a roof problem may actually originate from inside the house and not be related at all to the roof. And you don’t know how quickly a small problem (inexpensive) can become a major problem (expensive).