Dark, "dirty-looking" areas on your roof.

Possible causes: Environmental pollutants; vegetation, fungus or algae growth; loss of granules due to age of shingles.

Missing, cracked, or curling shingles.

Possible cause: Shingles have reached their useful life.

Excessive energy costs.

Possible cause: Insufficient attic ventilation causes heating/cooling system to run excessively.

Stains on interior ceilings and walls or mold and mildew growth.

Possible cause: Inadequate or faulty shingle underlayment allowing leakage, or inadequate ventilation.

Blistering and/or peeling of outside paint.

Possible cause: Excessive moisture or high humidity due to poor attic ventilation.

Leakage in attic after driving rain.

Possible causes: Leaky or inadequate shingle underlayment; deteriorated flashing.

Roof shingle, sheathing, and siding decay.

Possible cause: Poor attic ventilation.