Understanding Very Severe Hail (VSH) Ratings – Part 2
With new Very Severe Hail (VSH) requirements in place, it is important to understand the single-ply membranes and cover boards that can be utilized in approved systems. VSH requirements now include parts of 14 states as designated by Factory Mutual. VSH requirements can also appear in specifications outside of these 14 states.
The cover board is an essential part of a VSH singly-ply system. Common rooftop cover boards such as gypsum and HD polyiso are not approved, whereas cover boards with very high compressive strengths like plywood and OSB are approved. Outside of wood products, DuraStorm VSH is the only other approved product sourced from post-industrial and post-consumer waste streams. It has a compressive strength of nearly 4,000psi. You can learn more about DuraStorm VSH by clicking here.
Fleece-backed and bareback membranes can achieve VSH approvals; however, cover board attachment is critical. With fleece-backed membranes, the cover board can be mechanically attached using plates and fasteners or adhesively attached using a two-part polyurethane adhesive. With bareback membranes, the cover board can only be attached using a two-part polyurethane adhesive. See the chart below for clarification.
To learn more about Very Severe Hail (VSH) approved systems, contact Brandon Reynolds.
The cover board is an essential part of a VSH singly-ply system. Common rooftop cover boards such as gypsum and HD polyiso are not approved, whereas cover boards with very high compressive strengths like plywood and OSB are approved. Outside of wood products, DuraStorm VSH is the only other approved product sourced from post-industrial and post-consumer waste streams. It has a compressive strength of nearly 4,000psi. You can learn more about DuraStorm VSH by clicking here.
Fleece-backed and bareback membranes can achieve VSH approvals; however, cover board attachment is critical. With fleece-backed membranes, the cover board can be mechanically attached using plates and fasteners or adhesively attached using a two-part polyurethane adhesive. With bareback membranes, the cover board can only be attached using a two-part polyurethane adhesive. See the chart below for clarification.
| VSH Approved Membrane | 80-mil VersiWeld TPO | 115- and 135-mil VersiFleece TPO |
|---|---|---|
| Membrane Attachment | Roller or Spray Applied Bonding Adhesive | Full Spray/Splatter/4" Beads |
| VSH Approved Cover Board | DuraFaceR, DuraStorm VSH | DuraFaceR, DuraStorm VSH |
| Cover Board Attachment | Flexible DASH | Flexible DASH or Plates and Fasteners |
To learn more about Very Severe Hail (VSH) approved systems, contact Brandon Reynolds.
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Understanding Very Severe Hail (VSH) Ratings – Part 1
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