Asphalt shingles are a great, low cost option for homeowners and are the most common roofing system. Asphalt shingles are also most susceptible to storm damage and naturally degrade faster than other materials. There are several factors that determine how likely a repair will be successful:
1) The extent of the damage
If a significant portion of the roof is damaged, spot repair may not always be the best option
2) The condition of the roofing system
Sometimes, attempting to repair the roof can result in damage to the surrounding roofing material. If the condition of the roof has degraded past a certain point, manipulating surrounding material can cause tearing and other damage. At that point, full replacement may be the only way to ensure a successful repair.
3) The nature of the damage
If the reason for the repair is due to a defective roofing system or design, attempting to repair the area may prove difficult. Occasionally, roofing systems are installed incorrectly and extensive repairs could be necessary.