Hail Size Versus Typical Damages
|1/2" diameter and smaller
||Few, if any roofs damaged. Leaves stripped from bushes and trees; crops destroyed. Oxidation coatings on paint, wood, and metal spattered. Thin polyvinylehloride coatings on roofs cracked or broken. Thin aluminum vents, fins on air conditioning units, lead sleeves on soil stacks, window screens, and aluminum awnings dented.
||THRESHOLD SIZE FOR DAMAGE TO ROLL ROOFING AND DETERIORATED COMPOSITION SHINGS, especially where unsupported. Painted wood surfaces and deteriorated gray-black slates (especially at corners) chipped; most aluminum vents, flashings, valleys and siding dented.
||THRESHOLD SIZE FOR DAMAGE TO MOST LIGHTWEIGHT COMPOSITION SHINGLES. Thin and/or deteriorated wood shingles and shakes occasionally punctured or cracked. Singl pane windows and thin skylight shells cracked or broken.
|1 1/4" diameter
||THRESHOLD SIZE FOR DAMAGE TO MOST HEAVY COMPOSITION SHINGLES, WOOD SHINGLES, AND OLDER MEDIUM SHAKES. Blisters and other unsupported areas on built-up roofs punctured. Automobile body metal dented and (rarely) windshields cracked. Galvanized metal vents dented. Thicker skylights cracked or broken.
|1 1/2" diameter
||THRESHOLD SIZE FOR DAMAGE TO CLAY TILE, SLATE, AND NEW MEDIUM SHAKES. Serious denting of automobil body metal.
|1 3/4" diameter
||THRESHOLD SIZE FOR DAMAGE TO NEW HEAVY SHAKES. Metal vents caved in. Bare spots on built-up roofs bruised or punctured.
||THRESHOLD SIZE FOR DAMAGE TO NEW JUMBO SHAKES, MOST CONCRETE TILE, AND UNBALLASTED BUILT-UP ROOFING ON FLEXIBLE UNDERLAYMENT. (Note: Testing stopped at 2" stores. Gravel-ballasted, three-ply with base membrance were not damaged by 2" diameter stones, regarless of the underlying insulation system.)
These guidelines are for hard ice bailstones that strike the affected material perpendicular to it's surface. These general guidelines apply in most circumstances, but there are exceptions. In order to quantify hail damage accurately, test squares should be drawn on the roofs, and the number of hail-damaged units counted in each square.
Source: Haag Engineering Co.
2455 McIver Drive
Carrollton, TX 75006
REV JAN 94