Valleys are weak spots in roofing systems. They have a lesser slope than the adjacent roof planes. They erode faster because water is directed into them. Inspectors must look not only at visible flashing, but also at the adjacent roof covering, at least a couple of feet on either side.

Many roof problems are caused by issues with the framing and sheathing. In this section, we will focus on the defects that may be viewed from the exterior of the property. This is one of those cases where standing back and taking a good, hard look is better than getting "up close and personal" with the roof.

Chimney Flues

While the inspection of chimney flues is a highly specialized procedure, any obvious deficiencies in the flue should be noted. In particular, pay attention to flues that are damaged, collapsed, or show signs of previous chimney fires. Extra care must be taken when inspecting chimney systems that are being used to vent fossil-fuel appliances, such as boilers, furnaces, water heaters and manufactured fireplaces, as any deficiency in either the liner or the chimney structure could be a potential fire starter, or could allow carbon monoxide into the habitable space within the home. It is now required that any traditional flues being used as vents for these appliances be fitted with continuous metal flue liners to ensure that no noxious gases can find their way into the home. Compliments of InterNachi

Vent Problems

As with any other system, roof venting may have been installed incorrectly, may not have enough area, may have been rendered inoperable by changes to the home, or may have been badly modified by the homeowner in an attempt to save energy. Such problems include:

Poor ventilation causes many problems, not the least of which is substantial reduction in the lifespan of asphalt-based roof coverings....

Roof flashing are at least as important as the roof covering itself. A covering can be brand new, but unless the flashing are in a similar condition and properly installed, the roof is going to leak.

How to on gutters what to look for