Improper design: Inadequate roof slope, sagging, structures that excessively draw away under the load, inadequate draining and provision for expansion and contraction in decking material contribute to the roofing membrane weakening and splitting. Design deficiencies often can be corrected when identified with a roof replacement.

Hail: The impact of hail can loosen, fracture or remove granules from your asphalt shingles. The granules protect the asphalt matting of your shingles from sunlight and ultra violet light (U.V.). The asphalt will deteriorate very quickly once exposed to the sun. This is the reason a hail-damaged roof will prematurely fail. Hail-damaged roofs may or may not be detected by the inexperienced observer. The results of a hailstorm will void the shingles manufacturer’s warranty, as they cannot warranty against “Acts of God” such as hailstorms.

Rain: When water gets underneath shingles, shakes or other roofing materials, it can work its way to the roof deck and cause the roof structure to rot. Extra moisture encourages mildew and rot elsewhere in a house, including walls, ceilings, insulation and electrical systems.

Wind: High winds can lift shingles' edges (or other roofing materials) and force water and debris underneath them. Extremely high winds can cause extensive damage. Wind damage creates a partial vacuum from wind blowing over the edge of the roof. The low-pressure area tries to neutralize itself by bringing in air from a higher pressure area, typically from inside the building. Air pushing up on the bottom of the roof will loosen fasteners and break the roofing adhesion over time, which makes the roof susceptible to damage in the future. Quality roofing construction counteracts the effects of wind-uplift forces.

Snow and ice: Melting snow often refreezes at a roof’s overhang where the surface is cooler, forming an ice dam. This blocks proper drainage into the gutter. Water backs up under the shingles (or other roofing materials) and seeps into the interior. During the early melt stages, gutters and downspouts can be the first to fill with ice and may be damaged beyond repair.

Condensation: Condensation can result from the build-up of relatively warm, moisture-laden air. Moisture in a poorly ventilated attic promotes decay of wood sheathing and rafters, possibly destroying a roof structure. Sufficient attic ventilation can be achieved by installing larger or additional vents and will help alleviate problems because the attic air temperature will be closer to the outside air temperature.

Moss and algae: Moss can grow on moist wood shingles and shakes. Once it grows, moss holds even more moisture to a roof system's surface, causing rot. In addition, moss roots also can work their way into a wood deck and structure. Algae also grow in damp, shaded areas on wood or asphalt shingle roof systems. Besides creating a black-green stain, algae can retain moisture, causing rot and deterioration. Trees and bushes should be trimmed away from homes and buildings to eliminate damp, shaded areas, and gutters should be kept clean to ensure good drainage.

Trees and leaves: Tree branches touching a roof will scratch and gouge roofing materials when the branches are blown by the wind. Falling branches from overhanging trees can damage, or even puncture, shingles and other roofing materials. Leaves on a roof system's surface retain moisture and cause rot, and leaves in the gutters block drainage.

Missing or torn shingles: The key to a roof system's effectiveness is complete protection. When shingles are missing or torn off, a roof structure and home or building interior are vulnerable to water damage and rot. The problem is likely to spread, as well as allowing nearby shingles to rip easily and/or blow away. Missing or torn shingles should be replaced as soon as possible.

Shingle deterioration: When shingles are old and worn out, they curl, split and lose their waterproofing effectiveness. Weakened shingles easily are blown off, torn or lifted by wind gusts. The end result is structural rot and interior damage. A deteriorated roof system only gets worse with time. It should be replaced as soon as possible.

Flashing deterioration: Many apparent roof leaks really are flashing leaks. Without good, tight flashings around chimneys, vents, skylights and wall/roof junctions, water can enter a home or building and cause damage to walls, ceilings, insulation and electrical systems. Flashings should be checked as part of a biannual roof inspection and gutter cleaning.