Wind and snow design criteria by state

Every rooftop solar structural calculation starts with two numbers: the ultimate design wind speed (ASCE 7 V-ult) and the ground snow load. They drive uplift on every attachment and the added gravity load on the existing framing — and they are the first things a plan reviewer checks on the structural sheet.

Wind and snow design criteria by state

These are the statewide starting values OneLine Studio applies when a design has no jobsite-specific data. They are a starting point, not a substitute for a site-specific lookup — wind speed and ground snow vary enormously within a single state (elevation, coastline, special wind regions), and your AHJ may enforce a local amendment.

How these numbers get used

• Wind → uplift. Velocity pressure is qh = 0.00256 · Kz · Kzt · Kd · V², then the worst-zone component-and-cladding pressure is factored to ASD (×0.6). That governs the fastener pull-out check at every attachment.
• Snow → gravity. Ground snow p_g becomes a sloped roof load p_s through exposure, thermal and slope factors, and adds to the array's own dead load on the rafters.
• Both combine with the array dead load (typically 2.5–3.5 psf) in the load combinations an engineer checks before sealing.

Always confirm site-specific values

For a real submittal, pull the exact values for the address from the ASCE 7 Hazard Tool or your jurisdiction's adopted amendment. Our permit guides by jurisdiction list the criteria we hold for each AHJ we track, and structural review explained covers what a reviewer looks for. A licensed engineer must verify the existing framing before anyone seals the calculation.