So what is hail spatter, and why is it important? Did you know that a quick, preliminary inspection can provide great insight into a reported hail loss and better guide you during your detailed inspection?

A preliminary inspection can provide information such as directionality and size of the hail stones, potential debris patterns, and even whether or not hail was recently present at the risk location. A lot of this information can be determined by looking at hail spatter.

What is hail spatter?

Typically, painted components and exposed materials form a layer of oxidation, dirt, grime, or algae over time. Hail spatter is the temporary markings left by hailstone impact, which may or may not cause damage depending on how dense the hailstone is.

Why is hail spatter important?

Hail spatter removes the layer of dirt and grime, leaving behind a mark that can tell us how large and dense the hailstones were, what direction they came from, and how recently the hailstorm occurred.

Size of the hailstone

This diagram by InterNACHI shows how to measure spatter to determine the approximate size of the hailstone. These measurements are approximate because the spatter mark can vary based on the density of the hailstone. A softer hailstone will scatter more upon impact, leaving a misleadingly larger impact area.

A lot of research has been performed by engineers and roofing manufacturers to determine how large the hailstone must be to cause damage to different types of roofing materials. In the chart below by HAAG, you can see how large the hailstone needs to be to cause damage to the roofing material.

Roofing	Threshold
Lightweight asphalt shingles	1”
Heavyweight asphalt shingles and wood shingles	1¼”
Medium wood shingles and clay tiles	1½”
Concrete tiles	1¾”
Built-up roofing (smooth)	2”
Modified bitumen membranes	1½” to 2”
EPDM membranes (smooth)	2”
Other plastic singles-ply membranes (smooth)	1” to 2”
Membranes ballasted with gravel	2½”
Galvanized steel panels	2½”

Hailstone density

If you observe spatter on soft metals without denting or damage, the hailstone was not well formed and broke apart easily on impact. There would likely be little to no actual damage from this type of hail.

Time of hailstorm

Because hail spatter is temporary in nature, it can help you determine if the observed damage was caused by a recent event or possibly an older one. The main impact point of the hailstone will leave a clean, debris-free marking and typically takes a year or two to fade away. If spatter is missing and impact points have debris, dirt, or grime built back up in the dent, the damage is most likely from an older event.

Five areas to focus on during your preliminary inspection

Before you climb on a roof to look for damage, perform a preliminary inspection and look for the following:

1. Hail spatter on trash cans, electrical panels, siding, painted items, or fencing. Spatter on these areas can quickly tell you the approximate size of the hailstone and direction of the storm.
2. Denting or other damage to soft metals (fascia wrap, gutters and downspouts, aluminum siding, garage doors, etc.). These areas are more delicate than roofing and can be damaged by smaller hail impacts. Remember that hail falls at random, so if you begin to see patterns in soft metals like a straight line of dents in a gutter, it could be mechanical damage.
   

   Pro tip: Run your chalk sideways over dents to highlight the impact for your photo documentation.

3. Check the HVAC unit for exposed condenser fins, which are highly susceptible to impact damage, and look for spatter on the covers of the HVAC unit. These condenser fins are made of very soft metal and can easily exhibit signs of mechanical damage, so be thoughtful in your evaluation based on the location of the unit and the location and appearance of the impact.
   

   Pro tip: Take a photo of the ID badge on the HVAC units. The model number can sometimes be used to determine the tonnage of the unit, which is important for your estimation.

4. Look at the areas around the downspouts – do you see granules? Granular loss is part of general wear to the shingle but can also be caused by hail damage and be used as supporting evidence during your preliminary inspection.
5. Check the horizontally exposed surfaces such as windowsills, trim pop-outs, and light fixtures. Wood or aluminum-wrapped windowsills often show spatter or impact damage from hail, depending on the direction of the storm and the location of the window.

It may seem unnecessary, but a preliminary inspection for hail spatter can save you a lot of time on-site. Homes on opposite sides of a neighborhood can experience different levels of hail damage (some can experience no damage at all!) and hail size can vary greatly in the same area so you can only rely on evidence at the location of the risk. So the next time you’re inspecting a hail loss, take five minutes to perform a preliminary inspection!