A serious hailstorm can cause severe damage to your shingle roof. Here are some of the factors that will determine the amount of the damage you may be dealing with after a hailstorm:
The Size of the Hailstones
The size of the hailstones determines not only their weight but also the area of the roof that feels their direct impact. A circular hailstone with a three-inch diameter, for example, will cause more direct damage than a hailstone that is only an inch wide, assuming other factors are held constant. Therefore, if the hailstones reaching the grounds are big, assume that the same hailstones are hitting your roof, and expect considerable damage.
The Speed of the Hailstones
The momentum of the hailstones is one of the main factors determining the extent of the damage. The momentum is a factor of the speed and weight of the hailstones. This means that a small hailstone traveling at a high speed can cause the same damage as a relatively bigger hailstone traveling at a slower speed.
Different factors determine the speed of the hailstones; examples are prevailing wind speeds and the height at which the stones are formed. A hailstone that is formed at a great height will hit the roof at a high sped (and cause more damage) than another one formed at a lower speed. The effect will be worse if there is a strong wind blowing, because the wind will accelerate the hailstones, assuming they are roughly traveling in the same direction. Therefore, expect serious damage to your shingle roof if there is a strong wind blowing at the same time as the hailstorm.
The Density of the Hailstones
Hailstones are not created equal as far as their densities are concerned; some are denser than others. Denser hailstones, meaning those with a greater weight per unit volume, cause more damage due to their higher momentum. Denser hailstones appear darker than their lighter counterparts; you can use this to gauge whether a hailstorm is likely to have damaged the roof.
The Slope of the Roof
The angle at which the hailstones strike also determines the extent of the damage. Greater damage occurs when a hailstone hits the roof perpendicularly. This is why straight-falling hailstones cause more damage on flat roofs than a sloped roof.
The Age of the Roof
Lastly, the age of the roof will also determine how much damage it incurs during a hailstorm. This makes sense given that aging roofs typically have worn-out and deteriorated materials, which are typically weaker than relatively new roofing materials. For example, old roofing shingles are likely to have lost their protective granules, and this means they are more likely to experience hailstone damage than newer shingles that still have their granules intact.
You can use the above factors to gauge the extent of shingle damage after a hailstorm. However, if the hailstorm was particularly fierce, it's best to have the shingle roof professionally inspected and repaired – especially if it is old.