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Simulated Hail Impact Testing and Ball Burst Testing of EPDM Roofing Membrane

Industry

Healthcare

Location

Colorado

Services Involved

Forensic Testing

Year

2025

Experts Involved

Steven R. Smith, PE

The Problem

  • A health care center, covered with single-ply, ethylene propylene diene terpolymer (EPDM) roofing membrane, experienced significant hail impact.
  • Concern arose regarding whether the EPDM roofing membrane had been damaged by the hail and to what extent hail impact could have caused ruptures to the membrane.
  • The goal was to understand the extent of damage to the EPDM roofing system and confirm whether the hail event contributed to the damage observed.
Hospital View

The Solution

Haag’s forensic testing team, led by Steven R. Smith, PE, conducted a series of rigorous tests on EPDM roofing samples to simulate hail impacts and assess the material’s ability to withstand hail.

Simulated Hail Impact Testing:

  • Roof samples, including EPDM membrane bonded to substrates (fiberboard, gypsum, polyiso), were mounted and subjected to simulated hailstone impacts with diameters of 2 and 2-1/2 inches.
  • None of the samples ruptured at laboratory impact locations.
  • Results showed that hail impacts caused denting in substrates, with the deepest dent measuring just under 1/2 inch.

Ball Burst Testing:

  • Five specimens from each sample were tested for burst strength, following ASTM D6797 standards.
  • Testing revealed that the EPDM membrane would need to stretch by approximately 1-1/4 to 1-1/2 inches to rupture. Hailstones up to 2-1/2 inches in diameter did not produce sufficient stretching to rupture the membrane.
  • The burst strength tests showed values ranging from 122.5 lbf to 159.8 lbf, with displacement values around 1.23 to 1.47 inches.
Ball burst

The Outcome

The testing results confirmed that hailstones, even up to 2-1/2 inches in diameter, did not cause ruptures in the EPDM roofing membrane. The hailstones induced minor dents in the substrate below, but no significant damage was found to be consistent with hail-caused ruptures.

The analysis provided clear, scientifically backed evidence that the EPDM roofing membrane was not damaged by the hail event, aiding in the resolution of the case.

Impact Results

Sample
Impact
Size (inches)
Mass (pound)
Speed (fps)
Energy (ft-lbf)
Results
1
1
2
0.1431
106.5
25.23
dent in fiberboard (depth = 0.154 inch)
1
2
2-1/2
0.2820
112.6
55.57
dent in fiberboard (depth = 0.039 inch)
1
3
2-1/2
0.2777
119.0
61.12
dent in fiberboard (depth = 0.060 inch)
2
1
2
0.1406
105.4
24.28
dent in gypsum (depth = 0.191 inch)
2
2
2-1/2
0.2771
119.9
61.9
dent in gypsum (depth = 0.447 inch)
3
1
2
0.1408
108.9
25.95
dent in polyiso (depth = 0.303 inch)
3
2
2-1/2
0.2803
118.6
61.28
dent in polyiso (depth = 0.486 inch)

Burst Strength Values

Sample
Burst Strength (lbf)
Displacement (in)
1
156.7
1.46
2
122.5
1.47
3
159.8
1.23
Steven R. Smith, PE

Expert Highlight

Steven R. Smith, PE

Steven R. Smith, PE, a leading expert in forensic engineering and material testing, conducted the analysis. Steven’s deep understanding of material properties and testing protocols ensured precise results that supported the investigation.

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