A Roofs Performance is affected by numerous factors such as:

• Sun:  Heat and ultaviolet rays can cause roofing materials to deteriorate over time. Deterioration can occur faster on the sides facing west or south.
• 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 in other places of your house, including walls, ceilings, insulation and electrical systems.
• Wind: High winds can lift your shingles' edges and force water and debris underneath them. Extremely high winds can cause extensive damage.
• Snow and Ice:  Melting snow often freezes 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 and seeps into the interior. During the early melting stages gutters and downspouts can be the first to fill with ice and be damaged beyond repair or even torn off a house or building.
• Condensation:  Condensation can result from the buildup of relatively warm, moisture-laden air.  Moisture in a poorly ventilated attic promotes the 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 ouside air temperature.
• Moss and Algae:  Moss and algae can grow on moist wood shingles and shakes. Once it grows, moss and algae hold even more moisture to a roof system's surface 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 brances are blown by the wind. Falling branches from overhanging trees can damage, or even puncture shingles and other roofing materials.  Leaves on a roofs surface retain moisture and cause rot and leaves in the gutters block drainage.
• Missing or Torn Shingles:  The key to a roofs 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.  Nearby shingles are also ripped easily or blown 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 are easily blown off, torn or lifted by wind.  The end result is structural rot and interior damage.  A deteriorated roof system only get worse with time, and should be replaced as soon as possible.
• Flashing Deterioration:  Many apparent roof  leaks can really be 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.