Last time we talked about the forms, functions, and materials of roofs. This time let's take a look at some common roof problems.

Just like any other component of your house, roofs are subject to damage and deterioration. Unfortunately, due to a roof's prominent location, it receives the brunt of the ravages of wind, rain, sun, heat, cold, and other adverse factors.

Many of the most common roof problems relate back to the composition of roofing materials themselves-predominately asphaltic materials. Over a period of years, the actions of nature-especially the sun-tend to drive off the volatile components of these asphaltic materials, leaving them dull, hard and brittle.

While sunlight itself causes some of these problems, the heat can be particularly damaging. Excessive heat (usually caused by improper or inadequate vented space beneath the roof) causes very high roof temperatures, accelerating loss of volatiles. As this process continues, shingles tend to curl and crack, aggregate is lost from the shingle surface due to the combination of erosion and lack of retention, and the throats (or flutes) that channel water down the shingles begin to wear out. Similar problems can develop in joints and valleys where roofing cement and flashing begin to deteriorate.

Erosion, abrasion and other mechanical factors can cause roof problems. In this category I include not only roof damage caused by water moving across its surface (promoting erosion), but branches, wires, shovels, and/or other items scraping against a roof surface (abrasion), as well as structural stress, expansion and contraction, etcetera.

Ice is also an enemy of a roof. Sometimes due to drainage problems, roof slope, poor maintenance, and/or venting problems, ice dams can form along a roof's lower edge. Water (from rain or melting snow) then collects upslope of the ice dam and eventually works its way back up under the shingles, causing leaks inside the house.

Of course, the common denominator in all these problems is that they adversely effect a roof's ability to do its job. (As described last week, in simplest terms, a roof's job is to keep "bad things" out.)

One of the homeowner's advantages in all of this is that many of the problems described here are related to roof deterioration. This means that the conditions take some time to develop, giving the homeowner an opportunity to observe and correct the situation.

A notable exception to this gradual deterioration is ice dams described above. These can develop rather quickly on a roof prone to ice build-ups. If your roof is prone to such ice problems, a reputable contractor can explore corrective options with you ranging from the immediate, short-term solution of removing the ice build-up to long-term solutions that will prevent ice build-ups altogether.

I'm convinced that many roof problems go uncorrected (leading to larger, more costly problems) simply because the homeowner doesn't see or recognize the condition of his or her roof. Having your roof checked periodically by someone competent to do so is probably your best strategy to prevent minor roof problems from becoming major roof problems.